The Practical Methods of Organic Chemistry - LUDWIG GATTERMANN

THE PRACTICAL METHODSOF ORGANIC CHEMISTRY LUDWIG GATTERMANN, PH.D. PROFESSOR IN THE UNIVERSITY OF FREIBURG WITH NUMEROUS ILLUSTRATIONS TRANSLATED BY WILLIAM B. SCHOBER, P H . D . ASSISTANT PROFESSOR OF ORGANIC CHEMISTRY IN LEHIGH UNIVERSITY THE SECOND AMERICAN-FROM.THEFOURTH GERMAN EDITION THE gcrrfe MACMILLAN COMPANY 1909 All rights reserved LONDON: MACMILLAN & CO., LTD. COPYRIGHT, 1896, 1901, Bv T H E MACMILLAN COMPANY. First printed September, 1901. Reprinted September, 1903; July, 1905; January, 1906; October, 1907; February, 1909. J. S. CmMng & Co. — Berwick k Smith Co. Tym czarownym rekom, ktorych dotkniecie pokoj pozynosL TRANSLATOR'S PREFACE THE success of Professor Gattermann's book in the original has warranted its reproduction in English. The translation is intended for those students of chemistry who have not yet become sufficiently familiar with scientific German to be able to read it accurately without constant reference to a dictionary. To such students this translation is offered, in the hope that it will increase their interest in the science without causing a corresponding decrease in their efforts to acquire a knowledge of German, which is indispensable to every well-trained chemist. My grateful acknowledgments are due to my colleague, Dr. H. M. Ullmann, for many valuable suggestions, and to Professor Gattermann for his courtesy in pointing out several inaccuracies in the German edition. WILLIAM B. SCHOBER. SOUTH BETHLEHEM, PENNSYLVANIA, April, 1896. PREFACE THE present book has resulted primarily from the private needs of the author. If one is obliged to initiate a large number of students at the same time into organic laboratory work, it is frequently impossible, even with the best intentions, to direct the attention of each individual to the innumerable details of laboratory methods. In order that students, even in the absence of the instructor, can gain the assistance necessary for the carrying out of the common operations, a General Part, dealing with crystallisation, distillation, drying, analytical operations, etc., is given before the special directions for Preparations. In the composition of this General Part, it has been considered of more value to describe the most important operations in such a way that the beginner may be able to carry out the directions independently, rather than to give as fully as possible the numerous modifications of individual operations. In the Special Part, to each preparation are added general observations, which relate to the character and general significance of the reaction carried out in practice; and the result follows, that the student during the period given to laboratory work, becomes familiar with the most varied theoretical knowledge, which, acquired under these conditions adheres more firmly, as is well known, than if that knowledge were obtained exclusively from a purely theoretical Viu PREFACE book. And so the author hopes that his book, along with the excellent " Introductions " of E. Fischer and Levy, may here ar.d there win some friends. For the assistance given by his colleagues, in pointing out deficiencies of his work, the author will always be grateful. GATTERMANN. HEIDELBERG, August, 1S94. PREFACE TO THE SECOND AMERICAN EDITION IN the preparation of this new edition advantage has been taken of the opportunity offered to correct a number of errors in the first edition, and to make the text a reproduction of the fourth German edition of Professor Gattermann's book. In many cases the laboratory directions have been improved, a number of new illustrations have been added, and the Special Part now includes methods for the preparation of glycol, dimethylcyclohexenone, s-xylenol, phenylhydroxylamine, nitrosobenzene, p-tolyl aldehyde (Gattermann-Koch synthesis), salicylic aldehyde (Reimer and Tiemann's oxyaldehyde synthesis), cuprous chloride, the decomposition of inactive mandelic acid into its active constituents, and a zinc dust determination. The preparations of acetylene and acetylene tetrabromide have been omitted. WILLIAM B. SCHOBER. SOUTH BETHLEHEM, PENNSYLVANIA, May, 1901. Carius' Method . . . 112 2. . PAGE m Sublimation 14 Distillation D i s t i l l a t i o n with S t e a m S e p a r a t i o n of Liquid Mixtures. Quantitative Determination of Sulphur. Dumas' Method . . Reaction: Preparation of an Anhydride from the Acid-Chloride and the Sodium Salt of the Acid 127 . . . . Quantitative Determination of Nitrogen. Separation by E x t r a c t i o n . . . . Sulphur. . Hydrogen. Melting-point D r y i n g a n d Cleaning of Vessels . Carius' Method . . ^ m . Liebig's Method 72 75 81 85 98 SPECIAL PART I. Quantitative Determination of the Halogens.CONTENTS GENERAL PART Crystallisation . Quantitative Determination of Carbon and Hydrogen. . Nitrogen. . . and the Halogens . 121 3. Reaction: The Replacement of an Alcoholic Hydroxyl Group by a Halogen . 10 S a l t i n g Out . Reaction: Preparation of an Acid-Chloride from the Acid . . Decolourising. . # 41 47 „ -g 6 6 R e m o v a l of T a r r y Matter . yO ORGANIC ANALYTICAL METHODS Detection of Carbon. Drying Filtration H e a t i n g u n d e r Pressure . . ALIPHATIC SERIES 1. . Reaction: Reduction of a Nitro-Compound to an Amine . Reaction: (a) Reduction of a Nitro-Compound to a Hydroxylamine Derivative. Reaction: Reduction of a Nitro-Compound to an Azoxy-. Union with Bromine 166 Reaction: Replacement of Halogen Atoms by Alcoholic Hydroxyl Groups 171 TRANSITION FROM THE ALIPHATIC TO THE AROMATIC SERIES Dimethylcvclohexenone and s-Xylenol from Ethylidenebisacetacetic Ester (Ring Closing in a 1. 199 5.131 Reaction: Preparation of an Acid-Nitrile from an Acid-Amide . Reaction: Replacement of the Amido. AROMATIC SERIES 1. 13. . XI. 6. 8.139 Reaction: Oxidation of a Primary Alcohol to an Aldehyde . 143 Reaction: Preparation of a Primary Amine from an Acid-Amide of the next Higher Series 151 Reaction: Syntheses of Ketone Acid-Esters and Polyketones with Sodium and Sodium Alcoholate 155 Reaction: Syntheses of the Homologues of Acetic Acid by means of Malonic Ester 161 Reaction: preparation of a Hydrocarbon of the Ethylene Series by the Elimination of Water from an Alcohol. 9. . Reaction: Sulphonation of an Amine 208 7. 10.5 Diketone) II. 7. or Hydrazo-Compound . 135 Reaction: Preparation of an Acid-Ester from the Acid and Alcohol 137 Reaction: Substitution of Hydrogen by Chlorine . Azo-. (&) Oxidation of a Hydroxylamine Derivative to a Nitroso-Compound 196 4. . 210 176 . Reaction: Nitration of a Hydrocarbon 185 2. Reaction: Preparation of a Thiourea and a Mustard Oil from Carbon Disulphide and a Primary Amine 205 6. of the Acid ~ . .x£i CONTENTS PAGE 4. Reaction: Preparation of an Acid-Amide from the Ammonium Salt 5.188 3. . .and Diazo-Groups by Hydrogen . 12. R e a c t i o n : Nitration of a Phenol 24. . (l>) Replacement of the Hydrazine-Radical by Hydrogen and an Amine. . . . and Phosphorus Pentachloride 31. . Imido-. . . . Benzoin 27. . . . R e a c t i o n : Sulphonation of an Aromatic Hydrocarbon ( I ) or to a Thiophenol 2 1 . . R e a c t i o n : Oxidation of a Benzoin to a Bcnzil 28. R e a c t i o n : (a) Preparation of an Azo-Dye from a Diazo-Compound 13. 269 274 276 278 . . . . . 261 264 267 . R e a c t i o n : Reduction of a Quinone to a Hydroquinone . R e a c t i o n : Oxidation of an Amine to a Quinone 17. . or Reduction of a Diazo-Compound to a Hydrazine. R e a c t i o n : T h e Molecular Transformation of a Diazoamido-Com15.CONTENTS xiii PAGE 8. 12. . 19. . . R e a c t i o n : Addition of Hydrogen to an Ethylene Derivative . .217 221 223 229 235 238 239 243 244 249 253 258 10. . . . R e a c t i o n : Condensation of an Aldehyde by Potassium Cyanide to a 30. . R e a c t i o n : Preparation of an Aromatic Acid-Chloride from the Acid 32. . Reaction: Replacement of a Diazo-Group by Iodine Cyanogen 11. . R e a c t i o n : Fittig's Synthesis of a Hydrocarbon 16. . (l>) Reduction of the Azo-Compound . . R e a c t i o n : Simultaneous Oxidation and Reduction of an Aldehyde under the Influence of Concentrated Potassium Hydroxide . R e a c t i o n : Conversion of a Sulphonic Acid into a Phenol 23. . Chlorination of a Side-Chain of a Hydrocarbon. 279 285 288 289 290 . Bromine. . R e a c t i o n : Replacement of a Diazo-Group by Chlorine.216 . R e a c t i o n : Addition of Hydrocyanic Acid to an Aldehyde 29. . (£) Conversion of a Dichloride into an Aldehyde 25. . . . R e a c t i o n : Sulphonation of an Aromatic Hydrocarbon ( I I ) 22. . R e a c t i o n : Reduction of a Sulphonchloride to a Sulphinic Acid . . R e a c t i o n : T h e Schotten-Baumann Reaction for the Recognition of Compounds containing the Amido-. . R e a c t i o n : Replacement of the Diazo-Group by Hydroxyl 9. . R e a c t i o n : (a) 20. . . R e a c t i o n : Preparation of a Diazoamido-Compound pound into an Amidoazo-Compound . . . R e a c t i o n : Perkin's Synthesis of Cinnamic Acid 26. R e a c t i o n : (a) . or Hydroxyl-Group . . . R e a c t i o n : Bromination of an Aromatic Compound 18. 14. . 44. . Reaction: Oxidation of the Side-Chain of an Aromatic Compound . Reaction: Aldehyde Synthesis. Reaction: Condensation of Phthalic Anhydride with a Phenol to form a Phthalein 42. . Reaction: Reduction of a Ketone to a Hydrocarbon . (&) Preparation of" an Oxime. . . PYRIDINE OR QUINOLINE SERIES . . 41. . Reaction: Condensation of Phthalic Anhydride with a Phenol to an Anthraquinone Derivative . Reaction: The Pyridine Synthesis of Hantzsch 2. . Reaction: Zinc Dust Distillation . Reaction : Alizarin from Sodium /3-Anthraquinonemonosulphonate .xiv CONTENTS PAGE $Z. 348 350 350 • 35 1 . . . 2. . . Reimer and Tiemann . Reaction: Saponincation of an Acid-Nitrile 37. Chlorine Hydrochloric Acid Hydrobromic Acid Hydriodic Acid Ammonia Nitrous Acid Phosphorus Trichloride Phosphorus Oxychloride Phosphorus Pentachloride Sulphurous Acid . . .Reaction: (a) Friedel and Crafts' Ketone Synthesis. . 43. 10. . . 35. . . 36. • . 3$. 7. . III. . 5. Reaction: Preparation of a Dye of the Malachite Green Series . Reaction: Kolbe's Synthesis of Oxyacids 40. . . . 3. . 4. 343 343 345 345 348 348 . Reaction: Skraup's Quinoline Synthesis IV. Reaction: Synthesis of Oxyaldehydes. INORGANIC PART 1. 337 340 . . . 39. 292 301 303 307 309 312 316 320 323 330 331 333 335 1. Gattermann-Koch . 8. 9. Reaction: Condensation of Michler's Ketone with an Amine to a Dye of the Fuchsine Series . (c) Beckmann's Transformation of an Oxime 34. 6. 45. . . . . 1 5 . . . Cuprous Chloride . . • • • 3°° .CONTENTS XV PAGE 11. . - • • • • • • " • 357 ABBREVIATIONS . Lead Peroxide 14. . D e t e r m i n a t i o n of t h e V a l u e of Zinc D u s t INDEX . . Sodium . . . . . . 351 352 • 354 355 356 12. . . . • • • . Aluminium Chloride 13. CRYSTALLISATION. 2. even at the ordinary temperature.THE PRACTICAL METHODS OF ORGANIC CHEMISTRY GENERAL PART THE compounds directly obtained by means of chemical reactions are. In order to obtain the compound in uniform. etc. they must therefore be subjected to a process of purification before they can be further utilised. CRYSTALLISATION Methods of Crystallisation. 3. DISTILLATION. The dissolved compound then separates out in a crystallised form. while the dissolved impurities are retained by the mother-liquor. SUBLIMATION. only in rare cases. it is dissolved. by-products.. For this purpose the operations most frequently employed are : i. . usually with the aid of heat. that B I . as well as to separate it from impurities like filter-fibres. and allowed to cool gradually. inorganic substances. pure. filtered from the impurities remaining undissolved. in a proper solvent. — The crude solid product obtained directly as the result of a reaction is generally amorphous or not well crystallised. well-defined crystals. {Crystallisation by Cooling.) Many compounds are so easily soluble in all solvents. carbon disulphide. Less frequently used than these are : hydrochloric acid. the following substances are principally used: CLASS I. — The choice of a suitable solvent is often of great influence upon the success of an experiment. In order to find the most appropriate solvent. methyl alcohol. solution . in order to obtain crystals. Water. In this case. preliminary experiments are made in. The remaining portions are heated to boiling. naphthalene. Also mixtures of these: CLASS II.2 GENERAL PART they do not separate from their solutions on mere cooling. Ether. with small quantities of the solvents of Class I . nitrobenzene. Ether -f. etc. after the addition of more of the solvent if necessary. phenol. Glacial Acetic Acid. aniline. the following manner: successive small portions of the finely pulverised substance (a few milligrammes will suffice) are treated in small test-tubes. provisionally. Water -|.Ligroin. solvent naphtha.) Solvents. If solution takes place at the ordinary temperature.—As solvents for organic compounds. (Crystallisation by Evaporation. ethyl acetate. amyl alcohol. But rarely used are: pyridine. chloroform. left out of consideration. the solvent in question is. and others. until.Glacial Acetic Acid. Benzene. a portion of the solvent must be allowed to evaporate. in that a solid compound does not assume a completely characteristic appearance until it is uniformly crystallised. Water 4-Alcohol. Choice of the Solvent. Alcohol. Ligroin (Petroleum Ether). xylene. Benzene + Ligroin. or on gentle heating. toluene. acetone. In order to determine whether a separation of crystals will take place on cooling. Hence mixtures of these solvents can be frequently utilised with advantage. If a substance is easily soluble in all solvents. nitrobenzene. in this case the walls of the vessel a r e rubbed with. are preserved. experiments are made with the mixtures. a n d others. recourse must be had to crystallisation by evaporation. At times crystallisation does n o t occur on mere cooling. That solvent from which crystals separate out first is the most suitable. the portions under examination are again heated until solution takes place. according t o the conditions. or the solution is " seeded. by allowing the different solutions to stand some time in watch-glasses. — Class II. If t h e individual solvents of Class I. in a cool place. If these experiments have shown several solvents to be suitable. xylene.CRYSTALLISATION 3 takes place. as a rule. and this time are allowed to cool slowly. Frequently a compound dissolves in a solvent only on heating and yet does not crystallise o u t again on cooling. and an observation will show in which tube crystals have separated in the largest quantity. the hot solutions in the pure solvents are treated with more or less water. are shown to be unsuitable. toluene. difficultly soluble in water. If a compound is very difficultly soluble. especially if they are of easily soluble substances. Substances easily soluble in ether. i. in the manner just described. compounds of this class are said to be "sluggish" (trage). benzene.. and which consequently do not separate out on cooling. Compounds which are easily soluble in alcohol or glacial acetic acid. so that if from the main mass of the substance no crystals . crystallisation is frequently induced. The crystals obtained in these preliminary experi rnents. a small crystal of the crude product is placed in the solution. are.e. if necessary over night." i. a sharp-angled glass rod. often dissolve in ligroin with difficulty. etc. That solvent from which the best crystals separate in the largest quantity is selected for the crystallisation of the entire quantity of the substance. In this case. by this means. as toluene. phenol. The tubes are now cooled by contact with cold water. the solution may be allowed to stand for some time. aniline.e. solvents with high boilingpoints are used. heating may be done in a beaker on a wire gauze over a free flame if the quantity is small. The result is that a portion of the solvent must be evaporated or distilled off. in case it is moist. but on cooling nothing crystallises out. which involves a loss of time and substance. it is true. therefore. In working with large quantities of alcohol. ligroin. or other substances with low boilingpoints. as well as decomposition of the substance. no attempt to extinguish the flame by blowing on it should be made. the. but the burner is removed and the vessel covered with a watch-glass. the substance to be dissolved melts at the bottom of the vessel. benzene. Alcohol and benzene may alsb be heated in like manner directly over a moderately large flame. before dissolving. A substance to be crystallised from a solvent which is not miscible with water must be dried. is employed. or a solvent which is not inflammable or not easily inflammable. The following rule should. If the liquid becomes ignited. To dissolve the Substance. if large. In either case care must be taken to prevent the flask from breaking. When heat is applied.quantities. always be observed : The quantity of solvent taken at first should be insufficient to dissolve the substance completelyt even . a flask is always used.4 GENERAL PART can be obtained. by stirring up the crystals from the bottom with a glass rod. An error which even advanced students too often make in crystallising substances consists in this : an excessive quantity of the solvent is poured over the substance at once. they are heated on a water-bath in a flask provided with a vertical glass tube (air condenser) or a reflux condenser. solution takes place easily. a glass plate. or a wet cloth. or by frequently shaking the vessel. So much of the solvent has been taken that it holds the substance in solution even at ordinary temperatures. — When water or glacial acetic acid. This precaution is especially to be observed when. ether. The crystallisation of substances which boil without decomposition may often be facilitated by first subjecting them to distillation. carbon disulphide. thus inducing crystallisation. on heating. if the student has already had a sufficient amount of experience in laboratory work and does not use too large . the solution may be seeded. e. For filtration a funnel with a very short stem is generally used. The result of this is that on cooling nothing crystallises out. filter-fibres. On the addition of the first portions of the second liquid (water or ligroi'n) resinous impurities separate out at times. the filter . i). The funnel with a shortened stem or no stem is prepared with a folded filter. it becomes cooled to such an extent that crystals frequently separate out. Filtration of the Solution. etc. etc. The funnels used in analytical operations have the disadvantage that when a hot solution of a compound flows through the stem. In order to remove this cloudir/ess^ a small quantity of the first solvent is added. The beginner often makes the mistake here of adding more and more of the solvent to dissolve this last residue. If a mixture of two solvents is used. which for the most part generally consists of difficultly soluble impurities. these are filtered off before a further addition of the solvent is made. until all of the substance is just dissolved.CRYSTALLISATION 5 on heating. i.g. inorganic compounds. the solution must next be filtered from the insoluble impurities like by-products. in this case. an ordinary funnel the stem of which 'has been cut off close to the conical portion (Fig. thus causing an obstruction of the stem. In this way only is it certain that on cooling an abundant crystallisation will take place. e. In case the solution contains a substance that easily crystallises out. the substance is first dissolved in the former with the aid of heat. then ??iore of the solvent is gradually added. one of which dissolves the substance easily and the other with difficulty. At times it happens that the last portions of a compound will dissolve only with difficulty. like inorganic salts. In such cases the difficultly soluble portions may be allowed to remain undissolved. and on filtering the solution are retained by the filter. the heating is continued while small amounts of the second are gradually added (if water is used it is better to add it hot) until the first turbidity appearing does not vanish on further heating. — When a substance has been dissolved. alcohol and water. but is poured on the filter immediately after removing it from the flame or water-bath. see Fig. The solution to be filtered is not allowed to cool before filtering. Before filtering inflammable liquids. a n d filtered.6 GENERAL PART is made of rapid-filtering paper (Fig. I f large quantities of crystals appear in a FlG 2 solution as soon as it is poured on the filter. phenol. 53). p. 5). the flame with which the hot water or hot air funnel has been heated is extinguished. the point of the filter is pierced and the crystals are washed into the unfiltered portion of the solution with a fresh quantity of the solvent. Very difficultly soluble compounds crystallise during the filtration in the space between the filter and funnel. Under normal conditions. the solution is further diluted with the solvent. 2). If inflammable solvents are used. it is an indication that too small an amount of the solvent has been used. 3 and 4). they are somewhat warmed before filtering by immersion in warm Boiling nitrobenzene. This may be prevented when a small quantity of liquid is to be filtered. In order to prevent the thick-walled filter-flasks from being cracked by solvents of a high boiling-point. or the funnel may be surrounded by a cone of lead tubing wound around it through which steam is passed ( F i g . heated. If the quantity of the liquid is large. Substances which easily crystallise out again. After filtration the solution is poured into the proper crystallisation vessel. care must be taken that the vapours are not ignited by a neighbouring flame. In a case of this kind. in consequence of the contact of the solution with the cold walls of the funnel. hot water or hot air funnels may be u s e d (Figs. by warming the funnel previously in an air-bath. 38. or directly over a flame. Choice of the Crystallisation Vessel. may also be conveniently filtered with the aid of suction and a funnel having a large filtering surface (Btichner funnel. aniline. and similar substances may be filtered in the usual way through ordinary filter-paper. no crystals or only a few should separate out on the filter during filtration.—The size and form of the . in consequence of the complete evaporation of the solvent. 4. they contain all the impurities which should remain dis- FIG. since. the crusts collecting on the edges are very impure. since they cannot be heated over a free flame. in consequence of the rapid separation. If a compound will crystallise out on simple cooling. therefore.CRYSTALLISATION 7 crystallisation vessel is not without influence upon the separation of the crystals. 3. FIG.—Many compounds crystallise out in the beaker during nitration. without the necessity of evaporating a portion of the solvent. a beaker is used for the crystallisation. it is heated again until the crystals have redissolyed^ and is then allowed to cool as slowly . Heating after Filtration. The shallow dishes known as "crystallising dishes" are not recommended for this purpose. 5. The beaker is selected of such a size that the height of the solution placed in it is approximately equal to the diameter of the vessel. which is thus about one-half to two-thirds filled. involving a loss of the substance. The crystals thus obtained are never well formed. FIG. the solution easily " creeps " over the edge. Moreover. solved in the mother-liquor. and 'further. after the entire solution has been filtered. At times a compound separates out on cooling. Crystallisation. separates out in very coarse crystals. the convex surface of which is uppermost: the condensed vapours will thus flow down the walls of the beaker.g* the . but in a melted condition. the vessel is put in a cool place — in a cellar or ice-chest if practicable. the vessel is covered first with a piece of filter-paper and then with a watch-glass or glass plate. If a deposit of crystals as abundant as possible is desired. not in crystals. by allowing the solution to cool very slowly. Very coarse crystals are commonly more impure than smaller ones.8 GENERAL PART as possible without being disturbed. more of the solvent is then added. as soon as a slight turbidity shows itself. This may be caused by the solution being so concentrated that crystallisation already takes place at a temperature above the fusing-point. in case a sample of the substance for analysis is desired. The vessel must not be touched until the crystallisation is ended. The paper is used to prevent drops of the solvent formed by the vapours condensing on the cold cover-glass from falling into the solution. the quantity depending upon the conditions. Should a compound crystallise sluggishly. This difficulty may also be avoided. seeding the solution. by which the crystallisation would be disturbed. t. The paper need not be used if the vessel is covered with a watch-glass. In this case the solution is again heated until the oil which has separated out is dissolved. —In order to obtain as good crystals as possible. If a substance. or by seeding the solution with a crystal of the same substance. on slow cooling. under " Choice of the Solvent/' may be followed (rubbing the sides of the vessel with a glass rod. the solution is allowed to cool slowly without being disturbed. so that smaller crystals will separate out. In order to protect the solution from dust as well as to prevent it from cooling too rapidly. In exceptional cases only is it placed in cold water to hasten the separation of crystals. it is expedient. In other cases this may be prevented by rubbing the walls of the vessel a short time with a sharp-edged glass rod. in many cases. in that they enclose portions of the mother-liquor. the directions given on page 2. allowing to stand over night). to accelerate the crystallisation by artificial cooling. In the first case the crystals are spread . Drying of Crystals. etc. throughout the entire solution. obviously. This is done by first washing with a fresh quantity of the solvent. glacial acetic acid. the liquid. within a few seconds. After it has partially cooled.—When crystals have been freed from the mother-liquor they must be dried. then with a mixture of the solvent and a small quantity of the more volatile liquid. and never by merely pouring off the liquid. be displaced by water.CRYSTALLISATION g C L. like alcohol or ether. in this way. Glacial acetic acid may. At times the separation of crystals takes place suddenly. is heated until solution again takes place. The filter to be used is previously moistened with the same substance which was employed as the solvent. nitrobenzene. if the substance is easily soluble. and (2) at higher temperatures by heating on a waterbath or in an air-bath. formed on the sides and edges of the vessel by the complete evaporation of the solvent. Crusts.. and are worked up with the mother-liquor. eg. it must be removed from the crystals by a more volatile substance. the proportion of the latter in the washing mixture being gradually increased. they are removed with a spatula before the filtering. Separation of Crystals from the Mother-Liquor. they are then to be separated from the liquid (mother-liquor). they are washed several times with fresh portions of the solvent . those crystals which were taken out are now added to it. This may be effected ( i ) at the ordinary temperature by the gradual evaporation of the solvent in the air. are not filtered with the crystals .—When crystals have been deposited. In order to remove the last traces of the mother-liquor adhering to the crystals. toluene. This is always done with the aid of suction. until finally the volatile substance is used alone. by which a gradual crystallisation is caused. If a solvent that will not evaporate easily in the air or on the water-bath has been used. too large quantities of the solvent must not be used. after some of the crystals have been removed. I rv j7 / H ^ v beaker is placed in a larger vessel filled witrh i)ot water and'allowed J to cool in this. Since the crystals thus obtained are generally not well formed. in many cases it is advantageous to extract the last portions remaining in solution. a solution. if necessary. or a solution in ether or benzene with ligroin. In this case. — If a compound is so easily soluble in all solvents that it will only crystallise out on partial evaporation. which crystallise from a solvent miscible with ether. a solution in alcohol or glacial acetic acid may be diluted with water. in order to get good crystals. Compounds. then. Crystals may also be dried in a desiccator which is partially exhausted.—The mother-liquor filtered off from crystals still contains more or less of the substance. not too dilute. Crystallisation by Evaporation. one of the various forms of shallow dishes— the so-called crystallising dishes — is used. in -the manner indicated under "Drying of Crystals.I0 GENERAL PART out in a thin layer upon several thicknesses of filter-paper and covered with a watch-glass. is made. funnel. In drying substances at higher temperatures the crystal form may be lost by the fusion of the substance or by the separation of the water of crystallisation. The mother-liquor may also be diluted with a second liquid. Treatment of the Mother-Liquor. in proportion to its solubility at the ordinary temperature. can be very quickly dried by being washed several times with it. or similar vessel. In order that the vapours of the solvent may escape. and filtered from the impurities remaining undissolved. this is conveniently done by supporting it on several corks. a preliminary experiment with a small portion is always made when the drying is to be effected at higher temperatures.'1 Jn crystallising . not easily soluble in ether. as a crystallisation vessel. After a short exposure to the air they are dry.g. beaker. in which the dissolved substance is difficultly soluble. the covering must be so placed that the air is not shut off completely from the crystals. in which the solution is allowed partially to evaporate. A " second crystallisation " is obtained by distilling or evaporating off a portion of the solvent. Since many substances will liquefy far below their melting-point if they contain even small quantities of the solvent. e. by the aid of heat if necessary. In order to protect the vessel from dust. it is covered with a funnel or watch-glass. If. since. owing to capillary action. in no case must the solvent be allowed to evaporate completely. or sodium hydroxide. in order to obtain well-formed crystals. Fractional Crystallisation. — a task that is generally far more difficult th&n the crystallisation of an in . glacial acetic acid is absorbed by soda-lime. are removed with the aid of a small piece of filter-paper or a spatula.CRYSTALLISATION 11 by this method. If the quantity of crystals is very small. generally on the edges of the vessel. and the object of crystallisation was only to change it to a crystallised form. for the absorption of water or alcohol. with different substances. the solution is placed in a beaker or test-tube. which is then covered with filter-paper. but the crystals must be filtered off while still covered with the mother-liquor. calcium chloride or sulphuric acid is used. -r. Even though the substance is very soluble.Up to this point. according to the nature of the solvent. Evaporation may be hastened by placing the crystallisation' vessel in a desiccator. the vessel is never covered with filter-paper. will " creep " over the edge of the dish. The evaporation of all solvents may be hastened by exhausting the desiccator. it sometimes happens that the solution. crusts deposited. solid potassium hydroxide. it has been assumed that the substance to be crystallised possessed an essentially homogeneous nature. the mother-liquor adhering to the crystals is washed away with small quantities of the solvent. by placing them on porous plates (biscuit or gypsum) and moistening with a spray of the solvent. and with this are filtered off. the dish is placed on a watch-glass or glass plate. Under these conditions. To avoid loss of the substance from this source. Crystallisation is often employed for another purpose — that of separating a mixture of different substances into its individual constituents. in cases of necessity. Since the purifying effect of crystallisation depends upon the fact that the impurities remain dissolved in the mother-liquor. it may absorb the entire quantity of the substance. charged. the adhering mother-liquor may be separated. after standing some time. Before filtering. the solvent is to be evaporated as slowly as possible. it is frequently not difficult to find a solvent which will dissolve a considerable portion of the more easily soluble substance. An apparatus of this kind is represented in Figs. 6. s o i v e n k A c o r k bearing a reflux condenser —a ball condenser is convenient—is fitted in the opening at the upper end of the jacket. as is generally the case when a mixture of two different highly substituted compounds is under examination. FIG. a solution will be obtained containing all of the easily soluble substance and a small portion of the difficultly soluble substance. specially constructed apparatus — the so-called extraction apparatus — may be employed. The mixture has thus been divided into two fractions. the crystals are filtered off. The simplest case is one in which two substances are to be separated. This is filtered from the residue remaining undissolved. and but a small portion of the less soluble. the more insoluble compound will crystallise out. A shell of filter-paper is next prepared . This is connected with the flask that is to contain the FIG. bent as in Fig.If the crystallisation of the two fractions be repeated a second time. unaccompanied by any of the other compound. in not too large quantities. By evaporating the solution to a certain point. a complete separation will be effected. If the solubilities of the two substances are very different. 7. now. To a wide glass tube d is fused a narrow tube which acts as a siphon. the use of which possesses the advantage over the method of simple *h eating. For separating a mixture of this kind. 7. 6 and 7.12 GENERAL PART ual substance. This portion of the apparatus is surrounded by a glass jacket b. and the solution further evaporated. If. that much smaller quantities of the solvent are required. narrowed at its lower end. the mixture be treated with such a solvent. The condensed vapours drop from t h e condenser into the shell. One end of the roll must extend somewhat beyond the edge of the glass tube. a ball condenser is represented in Fig. The flask a. o n cooling. crystals of the second substance will appear. thread is loosely wound around its middle and upper portion. filter through t h e paper.CRYSTALLISATION i n the following manner: Three layers of filter-paper are rolled around a glass tube with half the diameter of the inner tube d. then. 8. and fill the space between shell and inner glass tube. the solution siphons off and flows back into the flask a. this is turned over and securely fastened with thread. A s soon as the liquid has reached the highest point of the siphontube. the solution is filtered with suction at once. under these conditions the crystallisation must be carefully watched. T o preserve the form of the roll. Occasionally. the former is marked with an arrow. The length of the roll is such that it extends i cm. above the highest point of the narrow siphon-tube. the substance which was prese n t in larger quantity generally crystallises out. ~a I f a mixture of this kind is dissolved. the upper end is closed b y a loose plug of absorbent cotton. . even though it is still warm. after standing some time. The amount of solvent used should be one and a half or two times t h e volume of the inner tube up to the highest point of the siphon. This operation may be continued as long as necessary. Comparatively easy also is the separation of two substances about equally soluble. dissolve the substance. I n the shell is placed the mixture of the easily soluble and difficultly soluble substance to be extracted . containing the solvent. T h e construction of. and as soon as crystals differing from those first appearing are observed. according to the nature of the solvent. In order to distinguish the tube by which the water enters from the outlet-tube. if the one i s present in larger quantity than the other. is now heated on a water-bath or over a free flame. sublimation is used to purify a solid compound. and others also have the power of uniting with other substances to form double compounds. Under these conditions the substance frequently condenses in crystals. e. If. benzene.g. the separation may be effected by picking out the crystals with small pincers or ^ quill. Double Compounds with the Solvent. The principle involved is this: A substance is converted by heat into the gaseous condition. it is possible to separate them by causing the lighter crystals to rise to the top of the liquid. the combined solvent is generally vaporised. when one of the compounds is heavier than the other. the combination of triphenylmethane with benzene may be mentioned in this connection. acetone.in needles by a sieve. and the liquid with the lighter compound floating in it can be poured off. It is well known that many substances. A compound crys^ tallising in leaflets can frequently be separated from one crystals Using. they may be separated bysifting through a suitable sieve or wire gauze. — Many substances crystallise from certain solvents in the form of double compounds. In many cases. one of the compounds crystallises in coars^ crystals. The sublimation of a small quantity of a substance can be con- . by imparting to it a rotatory motion by rapid stirring with a glass rod. composed of the substance and the solvent.. in crystallising from water. SUBLIMATION Much less frequently than crystallisation. Alcohol. as i ^ the case when they possess approximately the same solubility ancj are present in almost equal quantities. and the vapours are caused to condense again on a cold surface. In all these mechanical operations. and the other in small ones. The heavier compound collects at the bottom of the vessel. If these methods fail. combine with a certain portion of water. If double compounds of this kind are heated. As a familiar example. they can be separated me^ chanically. chloroform. the crystals must be a s dry as possible.14 GENERAL PART If two compounds crystallise simultaneously at the outset. In FIG. The plate is covered with a concave glass dish. it is covered with several layers of wet filter-paper a or with a small piece of wet cloth. the second watch-glass with its convex side uppermost is placed on it. a n d the two are held together by a watch-glass clamp. If the lower glass is now heated very slowly on a sand-bath with a free flame. The substance to be sublimed is placed on the lower one. which is then covered with a round filter perforated several times in its centre and projecting over the edges . 9). It consists of a hollow metal plate through which water flows. If large F quantities of a substance are to be sublimed. the conical opening is placed a crucible containing the substance to be sublimed. . 10. To prevent the escape of vapours. light crystals from falling back on the hot surface of t h e lower glass.SUBLIMATION veniently effected between two watch-glasses of the same size. the stem of t h e funnel is closed by a plug of cotton or is covered with a small cap of filter-paper. To keep the upper glass cool. t h e vaporised substance condenses on the cold surface of the upper watch-glass in crystals • t h e filter-paper prevents the very small. the upper watch-glass in the apparatus just described is replaced by a funnel somewhat smaller than the lower glass (Fig. 10). The apparatus for sublimation designed by Brtihl is admirably adapted to the purpose for which it is i n t e n d e d (Fig. 13). remains behind in the bulb.. In the distillation of low boiling . a larger volume of vapours which condense on cooling. In order to lead off the vapours rapidly. not only in size.16 GENERAL PART the ground edges of which fit the plate tightly. in that. etc. " There are two objections to distilling small quantities of a substance from a large flask: the vapours are easily overheated. a loss of the substance follows. thus giving a boiling-point that is too high. after the distillation is finished. tubes. When distillation is conducted at the atmospheric pressure. The crucible is heated directly with a small flame. DISTILLATION Kinds and Objects of Distillation. or to separate a mixture of substances boiling at different temperatures into its constituents. The heating may be done in an air. The glass cover is not removed until the apparatus is completely cold. than if a smaller flask had been used. n . 12. — By distillation is meant the conversion by heat of a solid or liquid substance into a vapour and the subsequent condensation of this.or oil-bath. In selecting a fractionating flask the following points are to be observed. it is called ordinary distillation . The object of distillation is either to test the purity of an individual substance by the determination of its boiling-point. These flasks differ. flasks. Sublimations can also be conducted in crucibles. — The heating of the substance to be distilled is generally effected in a fractionating flask (Figs. retorts. if in a partial vacuum. The vapours condense in part on the glass cover. (Fractional Distillation. beakers. vacuum distillation. as well as in the distance of the latter from the bulb. but more abundantly on the upper cold surface of the plate in crystals. while cold water flows through the plate. but in the diameter of the condensation-tube (side-tube).} Distillation Vessels. For distillation at the atmospheric pressure a flask is selected having a bulb of such a size that when it contains the substance to be distilled it will be about two-thirds filled. a current of an indifferentgas is sent through the apparatus. the nearer must the side-tube be to t h e bulb.DISTILLATION I 7 compounds. T h e higher a substance boils. in FIG. order that the vapours shall have as little opportunity as possible of condensing below the tube and flowing back into the bulb. 13. but the operation am be carried out more c . a fractionating ilask with a wide side-tube is used. as is the case when the mercury column is not entirely surrounded by the vapour. A fractional distillation can also be conducted in the fractionating flasks jusUdescribed. This can be converted into a fractionating flask with the aid of a cork bearing a T-tube. so that the entire thread of mercury of the thermometer employed is heated by the vapour of the liquid. an ordinary flask is used. as illustrated in Fig. If large quantities of a substance are to be distilled. By using a flask of this kind it is not necessary to correct the observed boiling-point. . For the distillation of solid substances which solidify in the condensation-tube. a flask is selected which has its condensation-tube as high as possible above the bulb. FIG. 11. 14. 14. Flasks of FIG. the round. this enables one to use the same cork with any flask. HEMPEL Fractionating Apparatus. WURTZ FIG. short-necked flasks such as represented in Fig. are well adapted to this purpose. 15). 16. These can be fused directly on the bulb or they can be attached to an ordinary flask by means of a cork (Fig. The value of these different forms of fractionating apparatus depends upon the fact that the higher boiling portions carried ^ along with the vapours do not pass immediately . LlNNEMANN this description can be obtained in different sizes but still possessing the same width of neck.18 GENERAL PART rapidly and more completely by the use of apparatus especially adapted to fractionating (Fig. 14) . 15. it is placed as far a b o v e the outlet tube as possible. this precaution is unnecessary. In the apparatus of Wurtz (a) the condensation takes place on the large upper surfaces of the bulbs. the fla. and since the expansion i s impeded by the clamp. Supporting the Fractionating Flask. More complete condensation is obtained in LinnemamVs apparatus (3). Since the lower "boiling portions condense to a liquid and collect in these. For the distillation of large quantities of a liquid the Hempel apparatus is • particularly well adapted. never below it. but before entering this they have an opportunity of condensing and flowing back into the flask. in working with i t as well as the Linnemann form. Experiments have shown that a single distillation with one of the forms of apparatus just described. T h e apparatus of Hempel is filled with l^lass beads which act like the sieves in t h e Linnemann apparatus. effects a more complete separat i o n than repeated fractionations in an ordinary fractionating flask. — If it is necessary to sxxpport the fractionating flask with a clamp. which differs from that of Wurtz in that the narrow tubes between the bulbs contain small platinum-wire sieves.sk frequently breaks. . the txeating must be interrupted from time IG x t o time. particularly if it is firmly attached. the glass exp a n d s by contact with the hot vapours.DISTILLATION 21 to the outlet tube. in order that the liquid col* * lecting in the beads or sieves may have an opportunity to flow t>ack to the distillation flask. since in this apparatus special tubes for conducting off the condensed liquid are joined t o the sides of the bulb somewhat above the sieves. the ascending vapours are so far cooled by the passage through them that the accompanying portions of the higher boiling substances are likewise condensed. If the Le Bel-Henninger form is xised. T h e most exact determinations of the boiling-point are obtained if tint entire thread of mercury is surrounded by the vapour of the substance. cork supporting the thermometer. the thermometer is thrust so far into the neck of t h e flask that the thermometer-bulb is somewhat below the outlet tube. if it does. and for those of . the graduation of the scale beginning at ioo°. thus preventing the temperature from being read. depending upon the height of the boilingpoint. With low boiling compounds this condition is easily obtained by the use of a fractionating flask having its outlet t u b e at a sufficient distance above the bulb. In order to avoid making a correction a special form of thermometer is used. the outlet tube of the fractionating flask is connected with a Liebig condenser by a cork (not a rubber stopper). or at other convenient points. from that portion of the cork which projects above the flask. 2oo°. the observed reading is corrected in the manner described below. a section is cut which will enable the scale to be seen. another flask must be used. In this case. so that the top of the mercury is visible. or if this is not possible.—The condensation of vapours is effected in various ways. Condensation of Vapours. By employing an instrument of this kind the mercury column may be kept in the vapours at any temperature. In making distillations. but the b u l b of the thermometer must not extend into the bulb of the flask and never into the liquid .18 rap1' GENERAL PART Supporting the Thermometer. In this case the thermometer is so placed that the degree corresponding to the boiling-point of the liquid is opposite the outlet tube. If a compound boils at a relatively low temperature (up t o ioo°). it occasionally happens that the mercury column ascends to that point in the scale which is hidden by t h e . if an exact determination of the boiling-point is desired.—The thermometer is passed through a cork (no rubber) which fits the neck of the flask. In a case of this kind the thermometer is either raised or lowered. For very low boiling compounds a long condenser is used. If i n dealing with high boiling compounds such an arrangement is not possible. the outlet tube of which is still higher above the bulb. the outlet tube is inserted far enough into the condenser or extension tube . 63). 18). is cooled by running water (Fig. a tubulated suction-flask may also be used. If the boiling-point of a compound is very low. long (extension tube) is connected by a cork (Fig. a condenser is always used. the tube finally becomes so hot that the vapours are not completely condensed. 17. the flask in which the condensed liquid collects (the receiver) is connected with the condenser by means of a cork and a bent adapter (Fig. for the condensation. and it is desired to avoid the loss of substance necessarily incident to the use of a condenser. connected to the condensing tube by a cork. If large quantities are to be distilled. With still higher boiling substances even this is superfluous. It is often unnecessary to employ running water for cooling purposes if to the outlet tube of the flask a wide glass tube 50 cm. provided it is not too short. If the boiling-point is moderately high.DISTILLATION high boiling-points a short one. the source of heat being a minute flame (the so-called microburner). the distillation even of low boiling compounds is conducted in a small distillation flask as slowly and carefully as possible. the receiver. and the receiver is cooled by ice or a freezing mixture. If the substance is to be distilled again. between ioo° and 2000. If a small quantity of a substance is to be distilled. will suffice FIG. 17). a fractionating flask is employed as a receiver. since the condensation tube of the fractionating flask. If the vapours of a substance attack corks. since when other condensation apparatus is employed. are thrown into the liquid (see below). which is heated gently or strongly as the case requires. of the flask from time to time in a vessel filled with warm water. — Low boiling substances (those boiling up to about 8o°) are not generally heated over the free flame. k Low boiling substances may also be heated by immersing the bulb FIG. The so-called microburner is well adapted to this purpose. If a substance is not distilled over a free flame.22 GENERAL PART so that the vapours do not come in contact with the cork. but on the waterbath gently or to full boiling. 18. in order to prevent " bumping " a few pieces of platinum wire or foil. But generally a cork is not used. the outlet tube being inserted sufficiently far into the condenser. High boil- . When a substance to be distilled is heated on the water-bath. Frequently it is more convenient to immerse the bulb of the fractionating flask as far as the level of the liquid which it contains in a dish or beaker filled with water. it may easily happen that the vapour inside the flask may be overheated by the steam escaping between the rings. For this reason. in the determination of exact boiling-points it is better to use a small free flame. Heating. or bits of glass. In heating. since the latter is likely to break easily on sudden heating.DISTILLATION 23 ing substances are always heated over the free flame. or during the distillation the burner may be placed under the flask and allowed to remain stationary. If now a free flame be applied. — If a substance which is not quite pure is -being treated. it is an indication that the heating is too strong. it is better to pass the flame back and forth slowly and uniformly over the bottom of the flask until the liquid is brought to incipient ebullition. particularly when ether has been used. In order to prevent this the flask is shaken repeatedly during the heating. It may also be prevented frequently by heating the flask on the side. Substances which have been previously dissolved. the flame is not placed under the flask at once. If vapours escape from the receiver. Toward the end of the distillation the burner is turned down somewhat. the temperature remaining constant. If there is only a small . this is collected separately in a small receiver. but in this case care must be taken not to apply the flame to the flask at any point above the liquid inside. the burner is held obliquely and not directly under the flask . then on distillation a small portion will generally pass over below the true boiling-point ("first runnings "). In this case the flask may be protected by heating it on a wire gauze . The size of the flame is so regulated that the condensed distillate flows into the receiver regularly in drops. and it is desired to test the purity by a determination of its boiling-point. often stubbornly refuse to give up the last portions of the solvent. To collect the Fractions. since an overheating of the vapours would result. During the actual distillation the heating may be continued by slowly passing the flame over the bottom of the flask as in the preliminary heating. passing over at the true boiling-point. it frequently happens that in consequence of a retarded boiling during which the solution becomes overheated. still by working carefully the gauze need not be used. since if the liquid is kept in motion. In order to protect the hand in case the flask should break. after the evaporation of the solvent on the water-bath. overheating cannot easily take place. a sudden active ebullition and foaming will take place. Then follows the principal fraction. as a basis for the fractions to be collected. at 2000. until finally. be collected with that portion which boils at the correct temperature. the entire quantity of phosphorus oxychloride does not pass over at about n o 0 . as in the example selected. a mixture consisting essentially of the higher boiling substance passes over. in spite of using a small flame. it is difficult. It is almost impossible to give definite rules of general application for fractional distillation. the boiling-points of the constituents lie far apart. this will cause a rise of the mercury The portion passing over a few degrees above the true boiling-point can.24 GENERAL PART quantity of the liquid in the bulb of the flask. p. and afterwards the benzoyl chloride at 2000. while the quantity of the former steadily decreases. However." The operation of fractional distillation is conducted in a wholly different manner. If this mixture is subjected to distillation. very commonly. A quantitative separation of the constituents of a mixture cannot be effected by the method of fractional distillation. as follows. in most cases. as is generally the case in preparation work. If but two substances are to be separated. no 0 ) and benzoyl chloride (b. p. the number of fractions to be collected depends upon the difference of the-boilingpoints. that of the latter increases. High boiling portions collected separately are designated as "last runnings. in preparation work. and upon other factors. to prevent the vapours from being somewhat overheated. 200 0 ). The preparation of benzoyl chloride (see page 289) will furnish a practical example of the method of procedure. it is possible to obtain fractions which contain the largest part of the individual constituents. The product of the reaction is a mixture of phosphorus oxychloride (b. particularly when. and a mixture consisting of a large quantity of the lower boiling substance and a small quantity of the higher boiling substance will pass over. but the distillation will begin below no°. the interval . the procedure is. upon the relative proportion of the compounds present. the temperature then rises gradually . This compound is obtained by treating benzoic acid with phosphorus pentachloride. without evil results. upon the number of compounds to be separated. by collecting the different fractions and repeating the distillation a number of times. i9O°-2O5° are collected. for benzoyl chloride. and the distillation is again continued : in this way the three fractions are collected. further. and the portion passing over up to 1400 is collected as in the first distillation in the empty receiver I.. Vacuum Distillation. The vacuum distillation is used advantageously for the fractionation of small quantities of a substance. 2000. the two end fractions are once more distilled separately. Fraction I.). and to the residue in the flask is added fraction III. 1400. since the separation of the individual constituents can be effected more rapidly and more completely than at the atmospheric pressure..). When the temperature reaches 1700.). a larger portion of these end fractions boil nearer the true boiling-points than in the first distillation. that from i4O o -i7o° in the empty receiver II.. and finally in another receiver that passing over between 1700 and 2000 (fraction III. up to 1400. which in the meantime has been washed and dried.. but now the lower and higher boiling fractions are much larger than the intermediate one . the distillation is stopped. then in another vessel the fraction passing over between i4o o -i7o° (fraction II. and the distillation continued. not volatile at the atmospheric pressure without decomposition. The portion passing over up to 1400 is collected in receiver I. is now redistilled from a smaller flask. in the case of the example selected the temperatures would be i io°. 1700.DISTILLATION 25 between the boiling-points is divided into three equal parts . and to the residue remaining in the flask is added fraction II. The fraction passing over between the temperature at which the distillation first begins. If it is now desired to obtain the two substances in question in a still purer condition. Vacuum Apparatus. and the portion passing over a few degrees above and below the true boiling-point. — Many compounds. is collected (fraction I. These are again distilled as in the first distillation. The quantities of the three fractions thus obtained are about equal. for phosphorus oxychloride about io5°-ii5°. may be distilled undecomposed in a partial vacuum. When the temperature reaches 1400. — The simplest form of a vacuum apparatus . the distillation is again interrupted. A thermometer is placed in the tube. 19. But this kind of flask is used only in case low boiling substances are to be distilled. h FIG. If it is desired to collect a larger number of fractions. 19.26 GENERAL PART is represented in Fig. its lower end being drawn out to a fine point. the object of which will be explained below. These simple forms of apparatus are used only when it is desired to collect a few fractions. may be used (Fig. for each new fraction. in order to get complete condensation of the vapours. since the contact of too hot liquids with the thick walls causes them to crack easily : this is likely to prove very destructive in vacuum distillation. Two fractionating flasks a and b are connected by a cork. the jacket of a Liebig condenser through which water is allowed to flow is fitted over the outlet tube of the fractionating flask. since it is troublesome to be obliged to change the receiver. With low boiling substances. In place of the flask b. a suction-flask such as finds application in filtering under pressure. 20). The neck of a is closed by a tightly fitting cork bearing the glass tube d. an . reaching to the bottom of the flask. and thus destroy the vacuum. Ordinary corks may also be used with almost equally good results.DISTILLATION 2 7 apparatus is employed by means of which the receiver can be changed without destroying the vacuum. 23 is also very convenient for fractional distillation in a vacuum. — In vacuum distillations the evolution of bubbles of vapour occurs to a much greater extent than under ordinary conditions. The receiver shown in Fig. 20. Brtihl's apparatus is very well adapted to this purpose (Figs. Construction of a Vacuum Apparatus. The individual parts of the apparatus are connected by rubber stoppers. By grasping the cork a and the tube c firmly with the fingers and turning. the different portions of the receiver may be brought under the condensing tube. a flask of such a size is selected. By turning the axis b} so arranged that it supports the receivers firmly. FIG. that when it contains the liquid it must in no case be more than half full. 21 a n d 22). each receiver may in turn be brought under the end of the condenser tube c. b u t only those are selected which are as free as possible from . it is better to have it but one-third full. In order to prevent the liquid from foaming up and passing over. prevent "bumping.28 GENERAL PART pores. 19: It is also a very excellent arrangement to use a two-hole cork. there is no difficulty in obtaining a vacuum. as in Fig. 21. with a thin layer of collodion. The capillary tube is made by drawing out a glass tube of 1--2 mm. the thermometer passing through one. they are pressed in a cork-press. the corks are coated FIG. the narrow hole in the cork through which this passes is made conveniently by a hot knitting-needle. If. 21. diameter.' Instead of using a * capillary tube to FIG. The thermometer and capillary tube may be arranged as showoyn Fig. after the apparatus is put together." other . and the capillary tube through the other. 22. and then very carefully bored. a short piece of thick-walled rubber tubing. A tube drawn out to a capillary point is secured in the limb a by a piece of thick-walled rubber tubing or a cork. with glass beads — obviously these are only to be used in the distillation of liquids not having a too high boiling-point — . The flasks recommended by Claisen (Fig. L f B R A means may be employed (see below)^. wholly. 24) may be used advantageously in vacuum distillations in place of the common fractionating flasks. When a tube drawn out to a capillary point is used. partially or FIG. e and c)9 is attached to the upper end. 19.DISTILLAT|(^D .^ 25§}t j ^ j r r prdirjaiy distillations.m vwhicji^case the mometer is supported in the fractionating. When a few large pieces of broken glass are placed in b. which can be closed by a screw pinch-cock (Fig. FIG. The thermometer is inserted in b. these flasks possess the advantage of preventing -porFIG. The space above the pieces of broken glass may be filled. tions of the liquid (even in cases of violent boiling) from being carried over into the condenser. 24. 23. 25. the lower tube of the Briihl apparatus is connected with a manometer (Fig. In order that the apparatus may be perfectly tight. In order to determine the efficiency of the vacuum. greased again or covered with more collodion. ends of the rubber tubing. Frequently the suction pump will not work satisfactorily. For the distillation of solids a fractionating flask with a wide. are covered with collodion after the apparatus is set up. 26). are covered with a thin layer of grease or vaseline. and in case a . The rubber tube attached to the suction is closed by a screw pinchcock which has been placed on it beforehand. the corks. bent sabre-shaped condensing tube is used (Fig. by the same kind of rubber tubing. the pinch-cock on the capillary tube is closed. 25). it happens. it is advisable to insert a thick-walled suction flask between the suction pump and manometer. it is then examined to see if it is stopped up. as well as the ground surfaces of the Briihl receiver. the suction attached. Before the distillation. For this purpose. and the rubber tubing is pushed farther over the ends of the glass. In case it is not. and after some time the manometer is read : this will indicate whether the desired vacuum has been obtained. by means of a thick-walled rubber tubing which will not collapse upon exhausting the apparatus. When the apparatus has been exhausted. the air must not be admitted suddenly. Since in consequence of the varying water pressure. the apparatus is tested to determine whether it will give the desired vacuum. If ordinary corks are used. for the sudden rushing in of the air may easily destroy the apparatus. as well as the ends of the tubing. or a better pump is used. the corks are pressed more firmly into the tubes. that the water from the suction pump may be forced into the manometer or receiver. at times. these. The other end of the manometer is connected with suction. by removing a rubber joint.30 GENERAL PART thus combining the advantages of a Hempel column with vacuum distillation. detaching it and opening the t u b e repeatedly for an instant at a time. A thermometer is immersed in the bath and the flame so regulated that the difference between the two thermometers is not greater than that mentioned. which will prevent the flask from c o m i n g in contact with the metal. otherwise . from the opening to the edge of the plate there is a straight narrow slit. controlled by a pinch-cock. The air current. violent ebullition) frequently occurs. the pinch-cock which has just been closed may be opened. as in the ordinary way. continuous current of air is drawn through the liquid. powdered talc. The temperature of the oil. bits of glass. The same effect may be obtained by placing certain substances i n the liquid — splinters of wood the size of a match. until the rushing sound made by the inflowing air ceases. through which the neck of the fractionating flask may pass . in exact experiments. the bottom is covered with a thin layer of asbestos. but the flame must be applied to the side. the pinch-cock on this is gradually opened and the air allowed to enter through it. pieces of porcelain. o r better a metallic air-bath (iron crucible).or paraffin-bath. After a test has shown t h a t the apparatus does not leak. thus keeping it in constant motion.it will be difficult to maintain a high vacuum. The latter is covered with a thick asbestos plate containing a round opening in the c e n t r e . Small pieces of pumice-stone bound with platinum . — In vacuum distillation the flask can be heated directly with a free flame.o r airbath should. The heating is not begun until the a p p a r a tus is exhausted. The same object may be accomplished most rapidly by closing the tubing leading to the suction with the fingers. or after disconnecting the rubber tubing from the suction. T o prevent this a slow.DISTILLATION 3x capillary tube has been used. The air-bath must not be too large. not be more than 200—300 higher than the boiling-point indicated by the thermometer. and not to the bottom of it. the liquid to be distilled is p o u r e d in the flask and the distillation begun. — In vacuum distillations a troublesome bumping (a sudden. scraps of platinum wire or foil. must not be allowed to enter too rapidly. Care must be taken to keep the flame constantly moving. Heating. To prevent Bumping. It is much more satisfactory and safer to use an oil. capillary tubes. then the following correction i s added : L(T—t) • 0. — If it is not possible in making an exact determination of the boiling-point to have the mercurial column entirely surrounded by the vapour of the liquid." R. the side-tube of which is at a sufficient distance from the bulb. Acetic acid Monochloracetic acid . Acetanilide 19° 84° 27° io8° 16 7 ° u8° 186° 132° 236 0 295° 99° 102° 105° 128° 128° Corrections of the Boiling-Point. For further details concerning vacuum distillation consult "Die Destination unter vermindertem Druck im Laboratorium.32 GENERAL PART wire also act satisfactorily. and whicht lies near the one in question. the following table is given : Substance. — In order that some idea maybe obtained as to the approximate lowering of the boiling-point. Boiling-point at Ordinary Pressure. Boiling-point at 12 mm. The difference between t h e corrected and observed boiling-points is applied to the boilingpoint of the first substance. The portion of t h e mercurial column not heated by the vapours — that portion above the side-tube — is read in degrees (Z). another substance. by diminishing the pressure.—An operation frequently employed in organic work is distilling off a solvent from the substance dis~ . Chlorbenzene p-Nitrotoluene . the temperature of which is also read (/). Lowering of the Boiling-Point. The so-called " corrected " boilingpoint may also be obtained as follows : The boiling-point iif> determined in the usual way. . Another thermometer is brought as near as possible to the middle point of this column. . the corrected boiling-point of which is known. or a sectional thermometer. is placed in the same flask and distilled under the same conditions.000154. . Difference. .— then a correction may be applied to the observed boiling-point in one of two ways. Distilling off a Solvent. If T is t h e observed boiling temperature. or both. after the distillation. — a condition usually obtained by employing a flask. Anschlitz. but the burner is extinguished. and attached by rubber tubing to the suction. ligroi'n. a second portion is added. alcohol. but always without a flame. then. this is warmed. Large quantities of solvents may also be evaporated by these two methods. Carbon disulphide. will be described first. The vaporisation is considerably accelerated by shaking the flask. carbon disulphide. on account of its great inflammability. supported firmly by a clamp. and the mouth covered with a watch-glass. the following method of procedure is recommended: A few cubic centimetres of the solution are placed in a sufficiently wide test-tube. The tube must at no time touch the liquid. and this is immersed in a larger vessel filled with warm water. When the boiling-point of the solvent is sufficiently far away from that of the dissolved substance. the flask removed from the batH with a cloth. like ether. Should the vapours become ignited from the flame of the water-bath. and when this has been evaporated. but the entire quantity is not treated at once. luminous flame. some small pieces of platinum wire or capillary tubes are placed in the liquid. the solution is poured into a small flask. that of the dissolved substance and the boiling-point of the solvent. and so on. no attempt to blow out the burning vapours should be made. a complete separation can be effected by a single distillation. ligroi'n. in case the solvent is ether. or carbon disulphide. and others. The methods used depend upon the quantity of the solution. extending to within a few centimetres of the level of the liquid. the evaporation is also facilitated by frequent shaking. The operation is more rapidly performed by heating the flask on a water-bath. over a small. The methods which can be used for distilling off low boiling solvents. is never vaporised in this way. D . For rapid evaporation of small quantities of ether. To prevent a sudden foaming.DISTILLATION 33 solved in it. A portion is placed in a small flask. and it is not worth the trouble to recover it by condensation. If a small quantity of a solvent is to be evaporated. with continuous shaking. due to retarded ebullition. The danger of ignition of the solvent may be avoided by inserting in the flask a glass tube. this event should always be expected. 27) the distillation of solvents is greatly facilitated. and the flask is heated by immersing it in a water-bath containing hot water. 28). since. or carbon disulphide. and the flame is easily extinguished by blowing on it or covering the mouth of the test-tube. it will ignite spontaneously without the intervention of a flame. ether and ligro'in can be distilled by continuous heating with a flame. The entire quantity of the liquid is not placed in the flask at once. and so on. FIG. By the use of the so-called safety waterbath. A piece of rubber tubing attached to the side tube of the receiver carries the vapours to a hood or below the surface of the table. the heating is interrupted for a moment. this. . the receiver is attached to the condenser tube by a cork. a silk thread as frayed as possible at the end reaching to the bottom of the flask is suspended from the neck and the flask is shaken frequently during the distillation (Fig. To prevent the liquid from being superheated. When it happens. and to recover it by condensation. the second is added. If it is desired to distil off a larger quantity of ether. and so on. the danger of ignition is lessened. If the tube is held as nearly horizontal as possible during the heating.34 GENERAL PART After the first portion is evaporated. By the use of a coil condenser (Fig. and should occasion no alarm. Since the vapours of the ether almost regularly become ignited. if it be surrounded by a cylinder of wire gauze. one in which the flame is surrounded by a wire gauze as in Davy's Safety Lamp. ligroin. another portion is added. 27. The free flame.e. It is not safe to distil off carbon disulphide even from this apparatus. when it becomes sufficiently hot. may be employed in place of a water-bath. but only a portion : after the solvent has been distilled off from. i. into the neck of which a dropping-funnel is inserted. Besides its convenient manipulation. This is an especially eco- . is connected with an ordinary condenser or an upright coil cpndenser. or in special cases. the water-bath may be heated with a flame.DISTILLATION 35 The apparatus best adapted to distilling off any desired quantity of ether is represented in Fig. the mouth of the receiver is closed by a loose plug of cotton. To protect the ether from ignition. During the heating by means of hot water. If the flow of the solution is regulated so that the same quantity of liquid is added as that distilled. the ethereal solution is allowed to flow gradually from the dropping-funnel into the flask in the bottom of which are a few scraps of platinum. A fractionating flask. or the receiver. the operation may be carried on continuously for hours. 28. is connected with the hood by rubber tubing. united to the condensing tube by a cork. 29. or the flask may be heated directly by a flame protected by a safety gauze. by pouring it into a larger vessel from time to time. The quantity of ether collected in the receiver is prevented from becoming too large. FIG. this method possesses the further advantage that after the completion of the distillation the dropping-funnel may be replaced by a thermometer. and the residue can be distilled directly from the fractionating flask. under these conditions the separation must be effected by a systematic fractional distillation with the aid of fractionating apparatus. The methods applicable to high boiling liquids have been given under "Distillation.36 GENERAL PART nomical procedure when the quantity of the dissolved substance is small. but ///. . the temperature is raised* and the distillation proceeds still more rapidly. and to always use threads. In a case of this kind the size of the flask is selected with reference to the residue that may be expected. Benzene can be distilled off under the same conditions as alcohol. 29. it is necessary to heat the water-bath continuously." (See page i6») In comparatively few cases the difference between the boilingpoints of the solvent'and the dissolved substance is a slight one. the water-bath. In distilling off alcohol. In this case especial care must be taken not to use too large quantities at one time. If one has had sufficient experience in laboratory work. may be distilled off by heating the flask on a wire gauze or sandbath over a flame. The distillation may be hastened b y placing the flask not upon. If a solution of common salt is employed in the bath. alcohol FIG. through the other hole passes the outlet tube bent at a right angle. Apparatus. 30. The distillation with steam is therefore to be regarded as a special case of distillation in a partial vacuum. the inlet tube is bent so that it may reach the lowest point of the flask. Steam is generated in a tin vessel about half-filled with water. The distillation flask selected is of such a size that the liquid fills it not more than half full. the other hole bears a short glass tube the end of which is just below the cork. but since at . or when steam is passed over or through them. Many substances. through one hole passes a not too narrow glass tube reaching to the bottom and serving to lead in the steam. The flask may be heated on a wire gauze over a free flame. — The apparatus used for distillation with steam is represented in Fig. is distillation with steam. A round flask inclined at an angle is closed by a two-hole cork. when heated with water. even those distilling far above ioo°. of volatilising with the steam.DISTILLATION WITH STEAM 37 DISTILLATION WITH STEAM A particular kind of distillation. the lower end of this tube does not touch the water. In order that the steam may act on an oil at the bottom of the flask. the other end is connected with a long condenser. This phenomenon finds its explanation in the fact that the atmospheric pressure acting upon the mixture is naturally divided between the steam and the other substance. very frequently employed in organic work for the purification or separation of a mixture. or those not volatile without decomposition. possess the property. the neck being closed by a two-hole stopper . Method of Procedure. in consequence the volatility is increased. so that the partial pressure upon the latter is accordingly less than the atmospheric pressure. the former conveniently by means of a low burner (Fletcher burner). — The experiment is begun by heating the steam generator and the flask simultaneously. into one hole is inserted a safety-tube partially filled with mercury. it may still contain considerable quantities of the dissolved substance. by the fact that the water passing over carries no drops of oil or crystals with it. . it is better. When the melting-point of the substance is above ioo°. so that only a small flask need be used. about 10 c c . otherwise the cold water coming in contact with the hot condenser may easily crack it. The end of the operation is indicated. In this case. But when the substance is soluble. If after this operation the water is to be turned into the condenser again.gg GENERAL PART times a very troublesome " bumping" will occur. the generator is being heated too strongly. and the flame should be lowered. even though the condensed water is apparently pure. The distillation is then continued until the condensed steam passes over unaccompanied by any of the substance. to heat on a briskly boiling water-bath. these may be removed provided the substance melts below ioo°. if the substance is difficultly soluble in water. the tubes of the two vessels are connected with rubber tubing. As soo# as the water in the generator boils and the liquid in the flask has been heated to the proper point. it must be done slowly at first. The substance is melted by the hot steam and flows into the receiver. the introduction of the latter may be omitted. a small quantity. If the substance to be distilled is solid. in order to keep the condenser free from crystals. and its vapour forms crystals in the condenser. by drawing off the water in the condenser for a short time. the preliminary and continued heating of the latter is superfluous: the steam can be passed at once into the cold liquid. To prevent the partial condensation of vapours in the upper cool part of the flask this should be covered with several layers of thick cloth to lessen the radiation of heat. Should the steam escape from the safety-tube. If the quantity of substance to be distilled is small. to determine when the end of the operation has been reached. in this case it is only necessary to mix the compound with several times its volume of water and distil directly from the flask. \i this happens. and the crystals are pushed out of the tube by a long glass rod. the distillation is interrupted for a short time. is collected in a test-tube. If a compound is very easily volatile with steam. DISTILLATION WITH STEAM 39 . a small opening is made in the steam exit and a piece of metal tubing affixed to it. . If no residue remains. flask (Fig. the ether decanted and evaporated. In order to superheat the steam. and then. the flame under the generator is extinguished. the distillation is finished. after this has been done. a large burner is placed under the spiral in such a position that the flame comes in contact with the interior of the spiral. This point is also carefully observed when the distillation is interrupted. it is frequently necessary to conduct the distillation with the aid of superheated steam. Since for many purposes it is necessary to use superheated steam at a definite temperature. 31. otherwise it may happen that the contents of the flask will be drawn back into the generator. After the distillation is ended the rubber tubing is first removed from the distilling flask. advantage is taken of this to decide the question. e.g. Under these conditions the substance to be distilled is not covered with a layer of water. 31). A thermometer is inserted into this tubulure and held in position by means of asbestos twine.or water-bath.40 GENERAL PART shaken tip with ether. A conically wound copper tube is interposed between the steam generator and the distilling FIG. When a substance shows a colour reaction. aniline with bleaching powder. The distillation is still further facilitated by heating the flask to a high temperature in an oil. Superheated Steam. — In dealing with very difficultly volatile compounds. and adhering to the sides of the stem. the so-called dropping funnel. If the quantity of liquid is so small that even a dropping funnel is too large. If. it can be done with a separating funnel (Fig. SALTING OUT Separation of Liquids. Separation by Extraction. the pipette is immersed in the mixture almost to the surface of contact of the two liquids in case the upper layer is to be removed. but which is not rniscible with the first liquid. it floats upon the water. generally water. If the lower layer is the one desired. If the liquid desired is of a greater specific gravity than that of water. is employed.—When a substance is held in suspension or dissolved in a liquid. and if one is accustomed to work with them. For the separation of small quantities of liquids a small separating funnel. and the liquid remaining is poured out of the top of the funnel By this manipulation the liquid is prevented from coming in contact with the portion of water remaining in the cock. SEPARATION BY EXTRACTION. a capillary pipette is used (Figs. and the operation conducted as before. The mixture to be separated is placed in a narrow test-tube. however. it is allowed to flow off through the stem by opening the cock. the latter is first allowed to flow off. one of which is for the most part water or a water solution. the pipette is immersed to the bottom of the test-tube.SEPARATION OF LIQUID MIXTURES SEPARATION OF LIQUID MIXTURES. is to be effected. 32). the test-tube is brought to the level of the eyes. and the upper layer drawn off. The tubing is then closed by pressure with the teeth or fingers and the pipette removed from the tube. drawing off this and . 33 and 34). — If the separation of large quantities of two non-miscible liquids. the removal of the dissolved substance may be effected by agitating the solution with another solvent which will more readily dissolve the substance. Pipettes of this kind are very easily made from glass tubing. are indispensable. allowed to stand. etc. benzene. ether is generally use£. In the discussion following it will be assumed that the extraction is made with ether. in special cases carbon disulphide. A similar method is followed if the substance is completely soluble in water. may be used. if a liquid. the oily layer is separated in a dropping funnel.. 34.GENERAL PART distilling it. and the ether evaporated. it is not immediately extracted with ether. drops. it is first filtered off. 33. chloroform. but' if the substance separating out is a solid. For extraction. FIG. If from an aqueous solution a considerable portion of a solid or liquid separates out. or if it is held in suspension by the water in the form of individual FIG. the two layers separated. amyl alcohol. ligroin. and then the filtrate is . If the liquid to be separated is insoluble in water and is present in such a small quantity that a direct separation would cause a loss owing to the adhesion of the liquid to the walls of the vessel. ether is added to the mixture. it is then shaken. or if a portion of it is soluble and the remainder held in suspension. in such a way as not to cause the two layers to be mixed by the shaking. when the layer of oil is very turbid. Under certain conditions the neck of the funnel may be closed with a cork bearing a glass tube attached to the suction. carbon disulphide. In many cases.g. e. If the test portion is evaporated by blowing the breath on it. due to the cold produced by the evaporation of the ether. the colouring of the ether does not show that it still contains any of the substance dissolved. This difficulty may be obviated either by stirring the liquids with a glass rod. The tendency is to continue the extraction until the ether is no longer coloured. Another error into which the beginner often falls when extracting with ether. in consequence of the formation of a flocculent precipitate floating in the liquids at the surface of contact. is this: in most chemical processes small quantities of coloured impurities are formed. or other low boiling solvents. In an extraction the following points are to be observed : Hot liquids are allowed to stand until they are cold before they are extracted with ether. It frequently happens that. leaves no residue. formed by the condensation of the moisture of the breath. or by giving the separating funnel a circular motion in a horizontal plane. and so on. the beginner will probably often be deceived by the appearance of an abundant quantity of crystals of ice. after long standing. With substances soluble in water the extraction must be repeated one or more times in proportion to the greater or less solubility of the substance. after the first extraction it is distilled off and used for the second extraction. evaporated on a watch-glass. on extraction. The bubbles of gas which now rise through the liquid frequently . the above-mentioned test gives the only safe indication of the presence of the substance. If it is desirable to avoid using large quantities of ether. the entire solution may be treated at once with ether. these impart a colour to the ether." The extraction is repeated until a test portion of the ethereal solution. or the solution strongly acid or alkaline. thus rendering filtration difficult.SEPARATION BY EXTRACTION 43 extracted with ether. two layers of liquids will not separate. On extracting colourless compounds. by this means the space over the liquid is exhausted. but the proper method of procedure is just the reverse of this. On opening the cock. and the eye is directed to the liquid at a point just above the cock. ammonium chloride. is added to the solution until no more will dissolve. potash. potassium chloride. In this case the separating funnel is held toward the light. can be separated out with ease. Under certain conditions both the ethereal and aqueous solutions are so coloured that they cannot be distinguished. by which the specific gravity of the aqueous solution is increased. By this method many compounds like alcohol. In this case water is added until the salts are redissolved. if. acetone. If the separation of the layers is very imperfect." Many substances soluble in pure water are insoluble or difficultlysoluble in an aqueous solution of certain salts. calcium chloride. If all of these methods prove ineffectual. or otber salt is added to the solution. they will separate out as solids. etc. The method of procedure is this : One of the above-mentioned salts. this is dissolved. in the evening a luminous flame is placed behind it.. as it approaches the opening. Some common salt is then added. Occasionally when extracting an aqueous solution containing inorganic salts with ether. sodium chloride.44 GENERAL PART destroy the troublesome emulsion. If the specific gravity of an ethereal solution is approximately the same as that of the water solution. the cause is often due to the fact that an insufficient quantity of ether has been used. in this case more ether is added. the eye will readily detect the layer separating the two liquids. with suction. Salting Out. which are so easily soluble in water that they cannot be removed from it by extraction with ether. Glauber's salt. which will retain the precipitate causing the emulsion. The substance . the separation often takes place only with difficulty. sodium acetate. best with the aid of a Biichner funnel. and the sub j stance previously in solution separates out. The same object may also be attained by adding a few drops of alcohol to the ether. then a complete separation may be obtained by first filtering the mixture. and then allowing it to stand. therefore. usually solid potash. ammonium sulphate. — A very valuable method to induce substances dissolved in water to separate out is known as "salting out. or the solution is filtered. If to the solution of a compound in water one of the salts mentioned is added — it is best to use finely pulverised sodium chloride — before the extraction with ether.c. a portion of the dissolved substance will separate out. then boiled with the animal charcoal and filtered. DECOLOURISING. it is allowed to cool somewhat. since when animal charcoal comes in contact with liquids heated nearly to the boiling-point. the latter is first dissolved in a suitable solvent. and finally. the ani- . a larger portion is dissolved by the ether than on treating the solution directly with it. instead of the salt. Before treating a hot solution. In many cases. a violent ebullition is frequently caused. the solubility of the substance in the the new solvent — sodium chloride solution — will be diminished so that on extracting. Among the reagents constantly used.DECOLOURISING. of the aqueous solution. while in the laboratories of technical chemists it has long been in daily use. In the first place. When a solvent not miscible with water is used. and an overflowing of the liquid may easily take place.the colour from certain solutions. The amount of sodium chloride to be added is about 25-30 grammes of the finely pulverised salt to 100 c. REMOVAL OF TARRY MATTER As is well known. animal charcoal possesses the property of being able to remove . Unfortunately the method of "salting out" has not been so generally adopted in scientific laboratories as it deserves. due to the " salting out" action. a concentrated aqueous solution may also be used. A combination of extraction and salting out also presents many advantages. ether does not dissolve so readily in a sodium chloride solution as in water. If it is to be used to remove the colour of a solid substance. REMOVAL OF TARRY MA1TER 4$ thus forced out of solution collects above the heavier salt-solution and is removed by decantation or suction. so that the volume of the ethereal solution is larger. a bottle of solid sodium chloride should not be wanting. furthermore. for this reason it is frequently employed'in the laboratory to free a colourless substance from coloured impurities. this latter is greatly facilitated for several reasons. to a deeply coloured solution. When substances to be analysed have bee. the general rule that no animal charcoal is ' added until the substance to be decolourised has completely dissolved. Very finely divided precipitates in water which pass through the filter may also be removed by the use of animal charcoal.g. especially when it is in a very finely "divided condition. In carrying out this operation. care must always be taken to prevent the contamination of the substance. This mixture ought to be of great advantage in the laboratory. so that by using much smaller quantities the same effect is obtained as with far larger quantities of . The solvent selected is such that upon cooling the decolourised solution. In such cases it is again crystallised without the use of animal charcoal. a larger quantity. a small quantity is added. the substance will crystallise out.n decolourised with animal charcoal. This may he prevented frequently. is previously dried on the water-bath. The quantity of animal charcoal to be added to a solution depends upon the intensity of the colour of the latter. should be followed. has the disadvantage that at times it passes through the filter and contaminates the filtrate. tin is precipitated with hydrogen sulphide. which is generally moist. the filtration presents no difficulty. e. the portion suspended in the water is decanted. and only the coarser residue which easily settles at the bottom is used. Recently the use of animal charcoal in the sugar industry has been replaced in part by a mixture of fine wood meal and floated infusorial earth (kieselguhr). To the mixture is ascribed verysuperior purifying properties.4g GENERAL PART mal charcoal. If the liquid is boiled with animal charcoal. This difficulty may also be prevented or essentially lessened. Under these conditions only. by washing the charcoal with water several times before using. is it certain that a portion of the substance does not remain undissolved mixed with the charcoal. When. To a solution very slightly coloured. for decolourising purposes. if used in the same way on a small scale. by filtering again. the tin sulphide is often so finely divided that it runs through the filter. or by boiling the filtrate a few minutes before the second filtration. The use of animal charcoal. The absorption of an oil may often be facilitated by moistening the substance on the plate with alcohol. but in a flask. Not only coloured impurities. Very easily oxidisable substances are not evaporated in a dish. In order to prevent an easily oxidisable liquid from decomposing when it is heated in the air—this action being generally attended with more or less colouration — a gaseous reducing or protecting agent is passed through it. or t h e substance is placed in layers of filter-paper between two wooden blocks. ether.DRYING 47 animal charcoal. For this purpose either a screw-press is used. so that it will be unnecessary to repeat the directions already given. the substances being firmly pressed out with a spatula in a thin layer. If one pressing out is insufficient. and generally employed in dealing with crude products will be referred to here. since in this the liquid is better protected from the action of the air. or only imperfectly crystallised. in so far as they are liquid or oily. sulphur dioxide. unused portion of the plate. the substance is spread out again upon a fresh. For the absorption of tarry impurities. Before a substance is dried by allowing it to lie in the air or in a desiccator. hydrogen sulphide. but those of a tarry character. porous plates (drying plates) may b e used with advantage. even if they are not crystallised. This method is naturally applicable to all solids. not so refined.g. — Under the chapter on "Crystallisation. which at times will dissolve the impurities without causing a solution of the substance. But a few methods. e. or carbon dioxide." page 9. the method of drying moist crystals has already been given. unglazed. Oily by-products may also be removed by pressing the substance between a number of layers of filterpaper. A mixture of wood meal and infusorial earth with which the solution may likewise be boiled is said to be of great value. or ligroin. or by . may also be removed by boiling with animal charcoal as above described. the upper one of which bears a heavy object DRYING Drying Solid Compounds. like ether. the paper. The upper hemisphere is enveloped in a cloth to prevent the condensation of the vapours. as follows: The substance lying between a number of layers of filter-paper is placed in a screw press. Drying Agents for Liquids. and is allowed to stand for some time. Smaller quantities of a substance may be pressed out between two wooden blocks. are used. the operation is repeated. the opening of which is closed by a cork bearing a glass tube bent at a right angle connected with suction. the upper of which bears a heavy object. until it is no longer moistened. two glass hemispheres. and the paper renewed. In order to dry a substance at a high temperature in a vacuum. If a solid is not contaminated by water or other solvent. The substance to be dried is pressed out in a thin layer upon a suitable piece of an unglazed porcelain plate. the greatest portion of the moisture is removed by pressure. using a fresh plate.48 GENERAL PART heating. Compounds which fuse without decomposition may be dried either upon the water-bath or in an air-bath. and pressure applied. Large masses of a compound not too finely granulated can be tied up in a piece of filter-cloth of fine texture. Very often solids may be dried by making use of the power of unglazed porcelain to absorb liquids with avidity. The upper vessel is supplied with a tubulure. longer or shorter. The operation is repeated. and then pouring off the water. but by a liquid by-product. If one pressing out is not sufficient. The most frequently employed drying agents are : . or in a solution of them. or by heating over a free flame until they melt. allowing them to solidify. Oily and tarry impurities may also be removed in this way. after it has absorbed this liquid substance. drying agents. can be extracted with a solvent. and pressure applied. with a spatula. which one desires to obtain. as mentioned above. Generally one places the blocks on the floor and stands on them. placed in the screw press. The sphere may be heated by immersion in a large quantity of hot water or on a boiling water-bath. as may be necessary. the edges of which are ground and fitted together. — Liquids are dried (deprived of water) either by placing in them. as is well known. — As . Still. (&) fused. 49 Less frequently used are : lime. it must be borne in mind that these drying agents may be contaminated. Sodium hydroxide. In the choice of a drying agent care must be taken to select one which will not react with the substance to be dried. phosphorus pentoxide. or liquids containing very little moisture. Further. The former acts more energetically. Caustic potash and caustic soda. Since these latter act upon bases. with potassium nitrite or sodium nitrite. react with acids and phenols to form salts. liquids may be . it is necessary to use the pure alkalies. — granulated and fused. it has the disadvantage of being more porous than the fused variety and in consequence of this porosity the loss of the substance being dried is greater. since it contains less water of crystallisation and possesses a larger acting surface. owing to the salt formation taking place. On drying bases with caustic potash or caustic soda. and others. acids are never dried with carbonates. These drying agents are never used with these substances. at times. For example. it is better.already mentioned. For drying small quantities of a substance. therefore. saponifying them. for drying these two classes of compounds. calcium chloride is never used. and upon esters. (a) granulated. anhydrous copper sulphate.METHODS OF DRYING Calcium chloride. anhydrous sodium carbonate. Ignited potash. Calcium chloride is employed in two forms. Fused sodium sulphate. decomposing them. sodium. Methods of Drying. calcium chloride unites to form double compounds with alcohols as well as with bases. or in place of them potassium carbonate or Glauber's salt. barium oxide. Consequently. Potassium hydroxide. to use fused calcium chloride. upon alcohols to form alcoholates. it must be treated in a separating funnel or the water drawn off with a capillary pipette: it is then dried. The drying of high boiling substances. adhering to the walls. the former is not drawn off through the cock of the vessel. So long as a liquid appears turbid. A liquid about to be dried must never contain drops of water which are visible . pipette. it is done before the solvent is distilled off. A small quantity of a substance or a viscous substance is designedly treated with a diluting agent. in case it does. to prevent a portion of the water from being carried along with the ethereal solution. If a solution of-a higher boiling compound is to be dried. the liquid is first filtered through a small folded filter. according to circumstances. but the separation of the two layers is effected by a separating funnel.SO GENERAL PART dried either in the undiluted form or in solution. and is then dried. or it is poured carefully into another vessel. so that the loss of the substance necessarily incident to the adhesion of the liquid to the drying agent cannot amount to a large percentage of the whole. . If a liquid contains very much moisture. milky liquids. or by decanting one of the layers. generally ether. without the use of a solvent. and this is the case especially in turbid. If only a few small drops of water are present. it has not been deprived of its moisture. The drying is accomplished by placing the drying agent in the liquid and allowing the two substances to remain in contact for a longer or shorter time. In this case a fresh quantity of the drying agent is not added at once. When a separation of an ethereal from an aqueous solution is to be made. as has already been mentioned. and the water drops will remain in the first vessel. it frequently happens that the drying agent will absorb enough water to dissolve itself and thus form an aqueous solution. if they are not volatile at the temperature of the water-bath. but is poured out of the mouth. may be greatly facilitated by heating them with the drying agent on the water-bath. The first method is followed when the quantity of the liquid is considerable. A similar rule obtains for undiluted liquids. Low boiling liquids are always dried directly. To obtain the small portions which adhere to the latter it may be washed with a small quantity of the dried solvent. it is poured off from the drying agent. Filtration with Suction. in order to effect the separation. be distilled without a previous separation from the drying agent. bent at a right angle. but he is advised to reread the chapter on Crystallisation (see page 1). the precipitates obtained in organic preparation work are filtered with pressure whenever it is possible. it is poured through a funnel containing a small quantity of glass wool.FILTRATION Before distilling a liquid which has been dried. which. however. If the liquid to be dried is of such a specific gravity that the drying agent will float in it. An ordinary flask may be converted into a suction flask by fitting to it a two-hole rubber stopper. through one hole is passed the stem FIG. then. of a funnel. under certain conditions. etc. in consequence of which the latter will dry more rapidly. the liquid may be much more completely separated from the precipitate. • The student lias already learned the methods of filtering without pressure in the operations of analytical chemistry. . — For filtering under pressure (suction). through the other a glass tube. The method presents a number of advantages : the filtration may be made in a much shorter time. FILTRATION While in analytical operations it is much more desirable to conduct nitrations without employing pressure. are rare. 35) is used. or asbestos. one end of which passes just through the cork. 35. a liquid not easily volatile may be dried by exposing it in a dish as shallow as possible in a partially exhausted desiccator. Low boiling individual liquids (boiling on water-bath) can. In some cases. a filtering flask a (suction flask) with a side-tube b (Fig. or before distilling off the solvent from such a liquid. This is one of the common methods of preventing foaming in general. the filter is made narrower or wider.g. as happens at times with alkaline liquids. as is represented in Fig. The suction surface may be increased by placing a so-called filter-plate of glass or porcelain in the funnel (Fig. . 36. or. If the funnel is imperfect in construction. as the case may be. in which is placed the filter. the filter-paper should be of two thicknesses. and does not possess the correct angle (6o°).52 GENERAL PART while the other is attached to the suction. in order that they may not be crushed by the atmospheric pressure on exhaustion. In order that the point of the filter not supported by the glass walls of the funnel. a test-tube is placed in the filter-flask. may not tear on exhaustion. If a platinum cone is not at hand. For this purpose flasks with thick walls are selected. If a filter-plate is used. rendered difficult. and upon this another round filter. The foaming may also be prevented at times by treating the filtrate with a few drops of alcohol or ether. it may be replaced by a conically folded piece of parchment paper or filter-cloth. 38). if a thin-walled flask is used. The funnel used is. the edge of which projects about 2-3 mm. the ordinary conical glass form. e. The pressure of the in-rushing air destroys the bubbles. in many cases. In the filtration of large quantities of substance it should always be used (Fig. if the filter has been moistened with water. The Biichner funnel is indispensable in working with organic substances. the substance dissolved in the alcohol may be precipitated in the pores of the filter by the water. 37). Upon the plate is first placed a round filter of exactly the same size as the plate. beyond that of the plate. When filtering very small quantities of a liquid. and an alcoholic solution is to be filtered through it. In consequence of its large suction surface. If a liquid foams excessively on filtering. it must be exhausted but slightly. a platinum cone c is previously placed in the funnel. The filter is moistened with the same liquid which is to be filtered. to accommodate it to the angle of the funnel. the rubber tubing is removed suddenly from time to time from the filter-flask. at least. a very rapid filtration is possible. otherwise it may happen that the filtration is prevented. This consists of a shallow dish with a perforated bottom. the joint being air-tight. and consequently are opaque. filtercloth may be used in its place. FIG. * * If this is also attacked. This apparatus is especially adapted to the filtration of larger quantities than can be conveniently treated in the Buchner funnel (Fig.FILTRATION S3 A double filter (described above) may be used in this. they must be carefully cleaned immediately after using. but in most cases a single filter is sufficient. 38. nitrocellulose cloth may b e u s e d . according to the nature of the precipitate. 37. If the solution t o b e filtered acts on the filter-paper. FIG. A fine or coarse meshed cloth is selected. 36. it is FiG 39 moistened before t h e filtration. which is fitted to t h e cover of a tubulated cylinder by means of a rubber ring. Similar to the Buchner funnel in its construction and a c t i o n is the so-called " N u t s c h " filter. 39). Since the Buchner funnels are made of porcelain. i t is made by treating a cloth woven from plant fibres with a mixture of . FIG. containing in this case a platinum cone. long fibrous asbestos. Filter-Press.— For the filtration of large quantities of substances which filter with difficulty. not too wide. like calcium sulphate. and for the most part is deposited on the exterior walls of the cell. When the suction is applied. PukalFs cells (porous cells). etc. with which the bottom of the funnel. and possess either the form of a cylinder or a mortar pestle. . or better. and is then drawn into the flask. Concentrated sulphuric acid may b e filtered through it. are very useful. — For the filtration of precipitates. The tube at each end projects slightly below the stopper (Fig. connected with a filter-flask. barium sulphate. especially dye-stuffs. closely fitting stopper bearing a glass tube bent twice at right angles. the liquid filters through the porous walls until the cell is filled. of strongly acid liquids. The operation is . made of unglazed clay. if necessary.. or asbestos. In cases of this kind the precipitate is retained by using glass wool. is filled. the precipitate remains behind in the vessel. as soon as a large quantity of the precipitate has accumulated. the suction is increased. until it almost touches the bottom. on account of their explosiveness. They may be procured in different sizes in the market. or it is spread out in thin layers over a filtering plate. Such cloth and other substances containing nitrocellulose must always be preserved under water. 40. 40). the suction is applied gently at the beginning of the filtration. contained in a beaker. or on the surface of a Biichner funnel Under these conditions. Very coarse-grained precipitates can be filtered without the use of a filter by placing in the point of an ordinary glass funnel a sphere of glass (a marbled : this is surrounded by glass wool. performed as follows : In the mouth of the cell is placed a FIG.54 GENERAL PART nitric and sulphuric acids. barium sulphate. Pukall Cells. The cell is now immersed in the liquid to be filtered. this is placed upon the cloth. which extends almost to the opposite side of the cell. . After a wide glass tubtg. 41). and finally the second plate. the cells are made as follows : At the bottom comes the perforated plate upon which is placed one layer of the filter-paper. one of which is attached near the glass 55 FIG. which consists of two perforated porcelain plates between which is a rubber ring. The first operation in working with the press is the preparation of the cells. after the cloth (linen or muslin) has been thoroughly moistened with water. filter-paper. and upon this the cloth. filter-presses are often used. 41.SEPARATION OF LIQUID MIXTURES calcium sulphate. The separation of the liquid from the precipitate is effected in the cell c>. The cell is now secu ed by three clamps. then follows the other piece of cloth. Two circular pieces of filter-cloth and two of filter-paper the same size as the plates are cut. of which the Hempel form will be described (Fig.. has been inserted into the opening of the rubber ring. etc. it forms a solid cake that can be removed without difficulty. and it is desired to obtain it. and the precipitate adhering to the sides scraped off with a spatula. By filtering with suction a complete separation of the liquid and precipiFIG. the pinch-cock on this is closed. Before it is connected with the vertical tube b. tate is effected. But if the precipitate is small. If it is desired to filter larger quantities of a precipitate than can conveniently be done in a single cell. The cock is again closed and the tube is connected with the cells. is . and the cock is now opened until the vertical tube is filled. The cell is now ready for the filtration. — Precipitates which are not too finely divided may be filtered off through a filter-cloth (muslin) stretched over a wooden frame (filter-frame) (Fig. water is poured into the funnel a. Filtering through Muslin. they are returned to the funnel. are poured into a beaker. the glass tube is withdrawn from the rubber ring. the contents of the cell. the liquid to be filtered poured into the funnel and the cock opened. so that it projects into the cell but a few centimetres. If the first portions run through turbid. If the precipitate is large enough to completely fill the interior space of the cell. 42). generally half-fluid. and is placed between the two corrugated glass plates d. the glass tube passing through the rubber ring is partly withdrawn. the cell taken apart. two cells connected by a Y-tube may be used. A square piece of muslin or linen.56 GENERAL PART tube. after being thoroughly moistened. and the others equally distant from this. This causes a canal to be formed in the cell from which the wash water can permeate the precipitate in all directions. 42. In order to wash the precipitate collecting in the cell. During the resulting filtration care is taken to keep the funnel partially filled so that the vertical tube is constantly full. folded together.FILTRATION 57 fastened on the four nails of the frame is such a way as to cause a shallow bag in the middle. . If it is desired after Washing the precipitate to press it out. the cloth is taken from the four corners. The frame is placed over a dish of the proper size and the liquid to be filtered is poured on the cloth and generally filters rapidly through it. The precipitate may be further dried. and then pressing it out carefully under a screw-press. by tying up the opening of the bag with twine. and squeezed with the hands. 43. they are generally heated in sealed tubes. The flame is then applied to the tube at a short distance from the opening.1). when the glass becomes soft. depending on the conditions. and as soon as the glass has become soft the tube is narrowed by drawing it out suddenly (II). Easily volatile substances as well as those giving off vapours. — If it is desired to induce a reaction between two substances at a temperature above their boiling-points. Sealing. it is heated at b. are transferred to the tube just before the sealing is to be done. and if the heating is not to be high. Never put solid or liquid substances directly in the tube. like hydrochloric and hydriodic acids. In withdrawing the funnel-tube care is taken to avoid bringing it in contact with the walls of the tube. In proportion to the temperature of the heating a greater or less pressure is developed. After breaking off or cutting off the end of the capillary tube at a. and then heated strongly in a larger non-luminous flame. when the tube is softened at this point it is drawn out slightly. difficultly fusible tubes of potash glass are used. In filling the tubes the following points are observed. a previously somewhat warmed glass rod is fused to it (Fig. since they are not so easily acted upon and do not crack so readily as the former. if the substances to be heated do not attack the glass or generate no gases. therefore more or less of the substance is placed in the tube. and in quantitative determinations always. But generally. it is warmed by holding it at an angle of about 45 °. The tube is never more than half-filled. . in the small luminous flame of a blast-lamp. Method of Filling.58 GENERAL PART HEATING UNDER PRESSURE Sealed Tubes. to allow the air to escape on further heating. If a quantitative determination is not to be made. — To seal the open end of a tube charged with the substance. but with the aid of a funnel-tube which should be as wide as possible when the substance is a solid. The tube is dried before placing the substance in it. which render the sealing of the tube difficult. soft glass tubes may be used. with constant turning. it is drawn out again. the capillary portion. but to give it a few turns in one direction and then to reverse the motion. w Ill 43. After sealing. If one . The narrowest part of the latter is then heated with a not too large flame without drawing it further. otherwise a spiral would be formed owing to the smalm ess of the glass at that point. the result is that the form of the end of the tube gradually changes from a cylinder to a sharp-pointed cone. the heated portion is cooled gradually by holding it in the luminous flame until it is blackened. and so on. 44. and there is thus obtained a thick-walled capillary tube which is melted off at the proper place (III). FIG.HEATING UNDER PRESSURE 59 the heat is applied just below 3. In the formation of -—a 1 L - ) —0 /A i • II FIG. Figure 44 shows the sealed portion of a tube in its natural size. it is desirable not to turn the tube in the manner previously directed. The sealing of hard glass tubes may be facilitated by placing a brick or tile near the flame in such a position that the heat will be reflected. The soft glass melts together. and this is used to draw out the tube. Under these conditions. this will cause the oxidation of the carbon. it may be attached to the blast-lamp in place of the blast. but the glass rod fused on is allowed to remain. To be able to carry out the operation of heating at a definite temperature. so that it will just admit a funnel-tube as narrow as possible. iodine. etc. The sealed tube is not heated directly. through a narrow tube into the upper part of the tube being sealed. ice.60 GENERAL PART is in possession of a cylinder of oxygen. The sealing is rendered less difficult by allowing the air to have free access to the tube. or by the decomposition of the substance with the evolution of troublesome products like carbon. but is slightly inclined from the horizontal. 45. the services of an assistant will be needed to givt to the vessel containing the cooling agent a circular motion corresponding to that of the tube. during the sealing the lower part of the tube is cooled by water. the tube is not drawn out first to a narrow tube. Under these conditions. but in a thick-walled protecting case of iron closed at one end. in which the glass tube is so placed that the capillary portion is at the open end. above the bottom of the iron tube. bearing a thermometer. in order that the evolved vapours may pass out unimpeded. covered with asbestos paper. as above. Heating. or a freezing mixture." of which a convenient form is represented in Fig. is fitted into the opening at the top of the furnace. a cork. The bulb of the thermometer must be about 1 cm. so that the glass tube may . In this case. When dealing with very volatile substances. during the heating. In transferring the glass tube to the iron casing the latter is not held vertically. The separation of carbon may be avoided by having an assistant direct a continuous current of air. In many cases the operation is rendered difficult by the vapours of the substance attacking the glass. it is often advisable to narrow the tube before charging it with the substance. the sealing may be effected with great ease. At the high temperature of the illuminating gas-oxygen flame.—The heating of sealed tubes (bombs) is conducted in the so-called "bomb-furnace. the gas tubes are raised and small flames used. rather than a lowering of the gas-tube and the corresponding increase in size FIG. Opening the Tubes. of flame. The tube is then resealed and heated again. 45. particularly in those in which a very high pressure is developed." The tubes are not heated at once up to the desired temperature. The danger of the bursting of the glass tubes may be diminished in many cases. If tubes are to be heated not higher than ioo°.HEATING UNDER PRESSURE 61 not be broken by suddenly striking the bottom. and allowing the gases which have been generated to escape. If it is desired to heat a furnace similar to the one represented to a low temperature. so that in case of an explosion the fragments of glass are not thrown out of the forward end but from the rear of the furnace. by interrupting the heating after a certain length of time. the convenient so-called "water-bath cannon" is used. A " fragment cage" renders the flying pieces of glass harmless. is removed from the furnace and held in a slightly . but are warmed gradually.—Sealed tubes must not be opened until after they are completely cold. The protecting case of iron. directed toward a wall. opening the capillary after the tube has completely cooled. The iron case is pushed into the furnace open end first. in which the case enclosing the tube is heated by steam at ordinary pressure. After the tube is in position the front opening is closed by a " drop-slide. in this case overheating is impossible. containing the tube. the capillary is opened by snipping off the end with pincers or tongs.52 GENERAL PART inclined position. often with such force as to extinguish the flame. the hand is protected from injury. obviously there is pressure. so that the contents may be emptied out. If on the softening of the glass the capillary is not blown out. In handling an unopened tube the greatest care possible must be observed. so that if the tube bursts. in consequence of the sudden diminution of pressure. the glass on becoming soft will be blown out and the gases will escape from the opening thus made. it sometimes happens. On opening. Under these conditions. if the latter is blown out in a long thin flame sidewise. To remove the end of the cone. On heating substances with hydriodic acid and phosphorus. The extreme end of the capillary is now held in the flame of a Bunsen burner. but the end of the tube is broken directly with a blow of a hammer. that the tube on being opened by a flame. In the latter case the substance is removed by heating. By means of a slight jerk the capillary end of the glass tube is caused to project from the iron case. and the seam of the case should be torn open. it is not necessary to proceed as described below. In order to break off the end of a tube after it has been opened. In case there is an internal pressure in the tube. In this case the explosion is due to the fact that the phosphine as well as the hydrogen evolved in the reaction have formed an explosive mixture with the oxygen of the air present in the tube. explodes. but in doing so the greatest care must be observed. it is held in such a position that neither the operator nor any one else can be injured in case of bursting. the end of the capillary being higher than the rear end. the procedure is as . If great pressure exists in a tube to be opened. it may be due to the absence of internal pressure or the tube may be stopped up by some of the substance. It is never removed from the iron casing to look at it or for any other purpose. before blowing the capillary the hand holding the iron casing is protected by a thick glove or a cloth is wrapped around the casing several times at the point where it is held. To show that there is an internal pressure the capillary is held after it has been opened near a small luminous flame. at a distance of \ cm. a thick iron wire. and on each side of it. a welldefined file mark is made. and the wire turned. a glass rod. Pressure Flasks. To prevent the fragments of glass from falling into the tube (when a quantitative determination is being made). finally. — In order to heat substances under pressure at a moderate temperature which on reacting with each other evolve no gaseous products. If this is heated to redness. the extreme end of it is again touched with a hot glass rod. If. contains about J of a litre.. the method of procedure is this : As before. and possesses the further advantage of being easy to seal. Volhard Tubes. previously heated to fusion in the blast-flame. not extending completely around the tube. . 11 the heated portion is moistened with a few drops of water. the end of the tube breaks off smoothly. the tube being constantly turned. If the crack caused by this does not extend entirely around the tube. . the narrowed portion becomes too short. kind of tubing is sealed on. wide is wrapped around the tube several times. so that no pressure due . It consists of a wide tube to the end of which a narrower one is fused. in diameter and 45 cm. . this causes the end to split off smoothly fl without splintering. j FIG. by which it is extended. the file mark touched with it. . That portion of the tube between the strips is heated by a small flame. . . If on opening the tube care be taken to cut off as small a portion of the narrow end as possible. a strip of moistened filter-paper 1 cm. and the breaking off will follow with certainty. a deep file mark is made. Autoclaves. — The tube described by Volhard (Fig. this is touched lightly with the hot end of.HEATING UNDER PRESSURE 63 follows : At that point of the tube where the cone begins. so that the conical end may be lifted off. another piece of the same . Instead of a glass rod. it may be used repeatedly. A tube of this kind. 46) may be used to great advantage when it is desired to heat large quantities of substances in a single tube. 35 mm. . 46. in length. If the glass does not crack at once. may be used. . the end of which has been bent around the iron casing to a semicircle. bronze or copper (autoclaves). thus giving i FlG 48 an excellent joint. The open end is cone-shaped. Such vessels are not suited for heating acid substances.use. and the cap made fast with a wrench. but may be used for neutral or alkaline substances. If the heating is to be carried beyond the point at which lead softens. one end being welded together. they are sometimes enclosed in strong-walled flasks (pressure flasks). the tube is then clamped in a vise. The flasks are not opened until after they are completely cold. one may not be burned by the hot water. The tube is closed by a threaded cap. which in section shows a cone. generally made of iron. of the kind represented in Fig. wrapped up in a cloth and heated in a water-bath.GENERAL PART to the reaction is developed. The water-bath is closed by a loosely fitting cover. but are slowly heated with the water. The heating may be * ' ' conducted in an oil-bath. FIG. so that in case the bottle bursts. 47. In this laboratory Mannesmann tubes (without seams) are in. In using them they are not immersed in water already heated. 47. the cover is screwed on as far as possible with the hand. Large quantities of substances which do not act on metals may be heated under pressure in closed vessels. and the other is supplied with a screw-thread and cap. After the substance has been put in. The conical end of the tube is pressed into the soft lead. Very well adapted to this purpose are the common soda-water or beer bottles. a . The cap is partially filled with lead. or directly in the bomb-furnace. for the preparation of the phenol ethers. For the packing a ring of lead or asbestos is used. e. . The lower portion contains oil in which the thermometer is placed. A slow current of water is passed through the condenser.HEATING UNDER PRESSURE 65 short metallic condenser about 10 cm.g. in length may be screwed on the threaded portion of the tube. The tube leading to the interior is designed for a thermometer. Another form of autoclave is represented in Fig. 48. Tubes of this kind have proved of excellent service in many cases. and so on. wide.66 GENERAL PART. wide is heated at one point while constantly turned. The apparatus most generally used for this purpose is represented in Figs. of characterising and of recognising a solid compound. Fig. The substance is placed in a small narrow tube (melting-point tube). into which is dropped a crystal of potassium nitrate the size of a pin-head. and is then drawn out from both ends to a tube 1 mm. The narrow tube thus produced is then fused off at its middle point. To transfer to the tube the substance the melt- . 49. 51 b represents the melting-point tube in its natural size. until it becomes soft. made in the following way: A glass tube 4-5 mm. to prevent it from becoming dark in colour. 51 <z. the portion lying next to that part of the glass tube which has not been drawn out is heated as before and is again drawn out. A long-necked flask is closed by a cork provided with several canals cut in the sides. MELTING-POINT In organic work the most common method of testing the purity. In order to prepare the melting-point tube from this a file-mark is made at the points indicated. FIG. A supply of several dozen of these is made and preserved in a closed bottle. 49 and 50. The bulb of the flask is two-thirds filled with pure concentrated sulphuric acid. the tube broken off and fused at the narrow end by holding it nearly vertical in a Bunsen flame. bearing a thermometer. There is thus produced a tube having the form represented in Fig. through which the heated air and vapours may escape. blast-lamp flame. is the determination of its melting-point. 50. in a small. FIG. it is observed that the previously opaque. if the flask should break. so that. it can be readily FIG. unfused substance suddenly becomes transparent and a meniscus is formed on its upper surface. the end of the tube dipped into it. The thermometer is now immersed in the sulphuric acid until the bulb is at about the centre of the liquid. The substance is placed at the middle point of the thermometer bulb. the hand would not be directly under it. and then slowly with a small flame so that the behaviour of the substance from degree to degree can be easily observed. it may be heated rapidly to within io c of this point.MELTING-POINT 67 ing-point of which is to be determined. it is packed by a thin glass rod or platinum wire. by gentle tapping the substance is caused to fall from the upper end to the bottom of the tube. 51. a b If the melting-point is not known. when brought in contact with the thermometer. It is safer to fasten the tube. ascertained on heating it rapidly to a high temperature. and in no case more than 2 mm. * In many cases when the temperature nears the meltingpoint this is shown by a softening of the substance before melt- . this. to the thermometer with a thin platinum wire or a rubber ring 1 mm. and then slowjy. wide. just below the mouth. uniform motion as in distillation. the flask is heated with a free flame which is given a continuous. heating rapidly until the temperature approaches the melting-point. sIf it is known at about what point the substance will melt. In order that it may not form a too loose layer. In this case the determination is repeated. The burner is inclined at a convenient angle. The height of the layer should be 1 mm. will cause it to adhere. The upper end of the tube may be touched with a drop of sulphuric acid. When the melting temperature is reached. To attach the tube different methods may be used. a small portion of it is pulverised. this may also be regarded as a characteristic of the substance. At times proximity t o the melting-point may also be recognised by the fact that the particles of the substance which adhered to the upper portion of the tube during the filling. a small portion is recrystallised and the melting-point again determined. If this phenomenon occurs the heating is conducted very slowly from degree to degree. melt before the mass of the substance . The liquid used may be water or sulphuric acid. if this takes place suddenly at a definite temperature. Instead of the apparatus just described the one represented in Fig. % I n determining the I a D2 * melting-point of a newly discovered substance. and since in the last few years it has happened that the explosion of minute quantities of a compound has shattered the melting-point . it is stirred by an up-anddown motion of the glass stirrer a. Many substances decompose on fusing. In order to keep the liquid at a uniform temperature. depending on the meltingpoint of the substance to be examined. since the hotter and therefore lighter layers of the acid rise to the top.68 GENERAL PART ing. it loosens from the walls of the tube and collects in the middle. if it melts sharply within one-half or a whole degree. the upper layers of the bath are heated somewhat higher than the lower. and if after repeated crystallisation the melting-point does not change. 52 serves very well for the same purpose. Since many compounds on heating decompose explosively. or in case of a substance with a high melting-point paraifin is placed in a beaker supported on a wire gauze. A substance is regarded as pure in most cases. one determination is not sufficient even if it is very sharp . In an analogous manner. to take the slight trouble of making a preliminary test by heating a small tube containing the substance directly in a small flame to the melting temperature. at least the cheaper varieties. or vaseline. There is thus obtained a table from which the corrections may be read directly. The test-tube is surrounded by a freezing mixture of ice and salt. the correction to be applied may be determined by slowly heating the thermometer to be tested by the side of the normal instrument in a bath of sulphuric acid. — At this point a few observations concerning the testing and correcting of the thermometer will be added. The true ioo° point is found by placing distilled water in a not too small fractionating flask and determining the boiling-point of it. the entire column of mercury being in the vapour. Since the boilingpoint is influenced by the pressure. pressure) may serve for the correction of the higher degrees. and by this means ascertaining if the substance will explode. are never exact. For many purposes it is sufficient to determine the deviation at only a few points. Since the ordinary thermometers. it is safer before the melting-point of a hitherto unknown substance is determined in the apparatus described above. The water is frequently agitated with the stirrer. e. Testing the Thermometer. the temperature at which crystals first begin to form is carefully noted. The mouth is closed by a cork bearing a thermometer dipping into the water. and noticing the reading of both thermometers for every io°. Through an opening cut out of the side of the cork is introduced a thick copper wire. the end of which is bent into a circle at a right angle to its length. and serious wounds have been caused by the hot sulphuric acid. the barometer must be read at .g.. pressure) and of benzophenone (3060 at 760 mm.MELTING-POINT 69 apparatus. in length is one-third filled with distilled water. glycerol. If a normal thermometer is at hand. the corrections for the degrees lying between these may be calculated by interpolation. they must be corrected before using. in diameter and 12 cm. the boiling-point of naphthalene (218° at 760 mm. the point to be considered as the true zero point may be determined as follows : A thick-walled test-tube of about 2. Thus.\ cm. In this case the procedure is as follows: The wet vessel is first drained as thoroughly as possible.3 2l6. and then heated with constant turning in a large luminous blast-flame.7 306.0 IOO. into which the substances. The alcohol and ether used for rinsing can frequently be used again.5 304. 720 mm. In order to dry small pieces of apparatus rapidly.7 DRYING AND CLEANING OF VESSELS While in analytical operations.I 306. Water. 725 73O 735 740 745 750 755 760 98.4 218. by means of a blast of air from bellows or other source.yQ GENERAL PART the same time with the thermometer and a correction. while. Naphthalene. applied.4 215-7° 303-5° 303-8 2I6. the cleaned vessels may be used even if wet. To remove the last portions of the easily volatile ether. the water vapour is driven out. they should be rinsed first with alcohol and then with ether.5O 98. or the ether vapours are removed by suction. may be poured. Pressure. air from a blast is blown through the vessel for a short time.I 304.2 217. it frequently happens in organic work.2 100. that dry vessels must be employed.9 99. after being used.6 216.O 216. It . Benzophenone.8 765 770 218.7 98.6 99.8 305.9 217. it is convenient to keep two separate bottles for the wash alcohol and wash ether.4 306.I 99-3 99-4 99.8 2I8. For rapid drying of large vessels this method is costly.8 100.2 304. taken from the table given below.5 217.2 3O5-5 3O5. since one generally deals with aqueous solutions. in experimenting with liquids not miscible with water. contains an amido (NH2) group. fuchsine. Vessels may be cleaned in part by rinsing them out with water with the use of a feather or flask-cleaner.g. are coloured brown by manganese dioxide. Thick-walled vessels like suction flasks must not be heated over a flame. In order to take away the unpleasant odour of the bleaching powder. and thereby destroyed. If the vessel contained a liquid not miscible with water. the hands are scrubbed with a brush. The second method is this: A thick paste of bleaching powder and a sodium carbonate solution is rubbed on the hands. and then afterwards with water. as just described. the hands are dipped into a dilute. in alcohol. The action of this latter may be strengthened by adding a little water to it. eg. The dye is diazotised. and may be removed by washing in water. This is removed by washing the hands with a little sulphurous acid.DRYING AND CLEANING OF VESSELS 71 may also be removed by careful heating and simultaneous suction. . a method for cleaning the hands may be mentioned if they are discoloured by dyes which cannot be removed by water. also by the addition of some crystals of potassium dichromate. This causes the oxidation and destruction of the dye as above. and are allowed to remain for some time. it is not washed out at once with water. the hands are immersed into a dilute solution of potassium permanganate1 to which some sulphuric acid has been added. are to be removed from a flask. but first with a small quantity of the solvent. and are then washed. the hands. Finally. If the last portions of the solution of a solid. . If the dye. weakly acid solution of sodium nitrite. Impurities of an acid character can. sulphuric acid for a long time. it is first washed with alcohol and then with water. Resinous or tarry impurities adhering firmly to the walls can be removed by crude concentrated sulphuric acid. the dye is oxidised. especially the nails. Crude concentrated nitric acid. is also used at times for cleaning purposes. After the permanganate has been washed off with water. The two methods following are applicable to all dyes. with sulphurous acid. be removed by caustic soda or caustic potash. but are dried by the first method. or a mixture of this with sulphuric acid. e. by which heat is generated . under certain conditions. At times the impurities adhere so firmly that the vessel must be allowed to stand in contact with. care being taken to remove the particles adhering to the upper and under surface of the nails. the original substance contained carbon. — To test an organic substance for nitrogen.c. it decomposes with charring. SULPHUR. it is boiled 1-2 minutes. while still hot it is dipped into a small beaker containing 10 c. The tube is finally heated to redness. and any potassium unacted upon becomes ignited. Carbon and hydrogen may be detected in one operation.GENERAL PART ORGANIC ANALYTICAL METHODS DETECTION OF CARBON. of water. it is an organic substance. which has been pressed between layers of filterpaper. HYDROGEN. small drops of water will collect in the upper cold part of the tube. is filtered from the carbon and glass fragments. placing the mixture in a small test-tube. to this solution is then added a small quantity of ferrous sulphate solution and ferric chloride solution. If the gas evolved (carbon dioxide) will cause a clear solution of barium hydroxide to become turbid. by mixing a small portion of the dried substance with several times its volume of ignited fine cupric oxide. After cooling. the tube being closed by a cork bearing a delivery tube bent twice at right angles. in a Bunsen flame until decomposition. A N D T H E HALOGENS Tests for Carbon and Hydrogen. generally accompanied by slight detonations and dark colouration. the alkaline liquid is acidified with hydrochloric acid. wide and 6 cm. by this the tube is shattered. about 5 mm. NITROGEN. if nitrogen was present in the substance. — If on heating a substance on platinum foil. potassium ferrocyanide will be formed. and if potassium cyanide was present. takes place. adding more cupric oxide to the to]) of the mixture. Test for Nitrogen. the filtrate treated with a few drops of caustic potash or caustic soda until it shows an alkaline reaction. and heating strongly. long. it is heated in a small test-tube of difficultly fusible glass. The aqueous solution containing potassium cyanide. if it also contained hydrogen. with a piece of bright potassium the size of a lentil. the . a longer tube is used and the portions of substance condensing in the upper cold part of the tube flow back a number of times on the potassium. cannot be tested in the manner described. sodium may also be used in most cases. just prepared by shaking a few crystals with water at the ordinary temperature. Accordingly. potassium. — The qualitative test for sulphur is made in the same manner as that for nitrogen. e. In place of potassium. if nitrogen was present. will form Berlin blue.02 grm.. this causes decomposition with evolution of ammonia. the precipitate will separate out In testing easily volatile substances for nitrogen. which is detected by its odour or by means of a black colour imparted to a piece of filter-paper moistened with a solution of mercurous nitrate. In dealing with a substance of this kind it must be determined whether on heating the substance with cupric oxide in a tube filled with carbon dioxide.2 grm. and being acted upon by the potassium ferrocyanide. but the former acts more certainly. a larger quantity of potassium or sodium than that given above is used (for 0. but only a bluish-green solution. of substance.ORGANIC ANALYTICAL METHODS 73 precipitated ferric and ferrous hydroxides will be dissolved. (See quantitative determination of nitrogen. otherwise only a yellow solution will "be formed. the presence of the latter may be proved by heating the substance with an excess of pulverised soda-lime in a test-tube with a Bunsen flame .g. under certain conditions. If this is allowed to stand some time. a blue precipitate is obtained. over night. If the substance contains only a small proportion of nitrogen. The substance is heated in a small tube with sodium. and to one-half of the solution is added a small quantity (a few drops) of a solution of sodium nitroprussiate. After the mass has cooled it is treated with water. eg. a gas is given off which is not absorbed by a solution of caustic potash. . do not give this reaction. In testing for nitrogen. Nitro-compounds. about 0.) In a limited number of substances containing nitrogen. diazo-compounds. Test for Sulphur. at times no precipitate is obtained at first. in order to prevent the formation of an alkali sulphocyanate). A violet colouration indicates the presence. in a substance containing sulphur. Substances which evolve nitrogen at moderate temperatures. or a small rod of the oxide \ cm. They are heated with fuming nitric acid in a bombtube to about 200 or 300°. therefore the second half of the solution is treated with a lead acetate solution and acidified with acetic acid. or a more or less heavy precipitate will appear. the solution is then filtered and treated with silver nitrate. the substance to be tested is heated in a not too narrow test-tube with a Bunsen flame with an excess of chemically pure lime. After diluting with water the solution is tested with barium chloride for sulphuric acid.e. as is the case in solutions of the inorganic salts of the halogen hydracids. In proportion to the amount of lead sulphide formed. and heated in the Btmsen flame until it becomes . since. long.) Test for the Halogens. i. the other end of which is fused to a glass handle. bromine. that the solutions of the same do not contain free halogen ions. This is explained by the fact that most organic compounds are non-electrolytes. like the sodium halides. a test for the halogens may be made by the same method given for nitrogen — heating with sodium. is acidified with nitric acid and silver nitrate added. the liquid will assume a dark colour. filtered from the decomposition products and fragments of glass. chemically pure nitric acid is added to acid reaction. as shown above. reacts with silver nitrate. in this way indicating the original quantity of sulphur. these on fusion with sodium give sodium cyanide. which. and iodine in organic compounds can only in rare cases be shown by precipitation with silver nitrate. Substances" containing nitrogen cannot be tested in this way for the halogens. (See method for the quantitative determination of sulphur.—The presence of chlorine. In compounds containing no nitrogen.GENERAL PART of sulphur. Since the nitroprussiate reaction is very delicate. The presence of halogens may be recognised very quickly and conveniently by Beilstein's test A piece of cupric oxide the size of a lentil. the tube while still hot is dipped into a little water. In order to detect the halogens. Easily volatile substances cannot usually be tested by this method. no conclusion as to the amount of sulphur can be drawn from the test. In this case the solution. is wrapped around with a thin platinum wire. 4. with the help of a spatula. and funnel-tube have been cleaned with distilled water. length about 50 cm. and adding a few drops of a silver nitrate solution. A funnel-tube about 40 cm. This soon vanishes. Drying. outside diameter. thickness of walls. about 2 mm.. Requisites for the analysis : 1. outside diameter. about 6-8 mm. conclusions may be drawn concerning the presence of a trace or more of the halogen in the original substance. bomb-tubes. Into this.. long.c. but by heating over a flame.ORGANIC ANALYTICAL METHODS 75 colourless. a minute particle of the substance containing a halogen is placed on this and then heated in the outer part of the flame. by which it is completely decomposed (oxidised). Filling and Sealing the Tube. and there appears a green or bluish-green colour due to the vaporisation of the copper halide. A tube of difficultly fusible glass sealed at one end. If after cooling.. 3. is placed . From the length of time the colour is visible. 7 cm. they are dried. The purity of the latter is tested by diluting 2 c. weighingtube. — After the bomb-tube.). of it with 50 c.c. QUANTITATIVE DETERMINATION OP THE HALOGENS CARIUS' METHOD The method consists in heating a weighed amount of the substance to be analysed in a sealed glass tube with silver nitrate and fuming nitric acid. (See page 70. of distilled water. the carbon burns first and a luminous flame is noticed. A weighing-tube of hard glass (length.) The exact weight of the weighing-tube is next determined. 18-20 mm.) 2. Solid silver nitrate and pure fuming nitric acid. for transferring the silver nitrate and nitric acid to the glass tube. and weighing the quantity of the silver halide thus formed. not with alcohol and ether. (Sealing-tubes. Neither an opalescence nor a precipitate should appear. In dealing with easily volatile sub^ f stances. After removing the funnel-tube. The temperature and time of heating depend upon the greater or less ease with which the compound is decomposed. 2 gramme of the substance to be analysed. so that the heating may be begun the. finely powdered The open end of the tube is wiped off with a cloth. If the substance to be analysed is liquid. while aromatic compounds must be heated 8-10 hours. it is placed in the weighing-tube with a capillary pipette. as by violently shaking the tube.j§ GENERAL PART 0. and the exact weight of the tube plus the substance is found. otherwise the procedure is just as described.5 gramme of finely powdered silver nitrate is transferred to the bomb-tube (a correspondingly larger amount up to 1 gramme is used for substances containing a high percentage of halogen) and 2 c. With the aid of the funnel-tube. the tube is transferred to the iron protecting case. but the substance must not come in contact with the acid. and finally up to 250-300 0 . the weighing-tube is inserted in the bomb held at a slight angle. of fuming nitric acid. it is necessary to heat aliphatic compounds 2-4 hours at a temperature of 150-2500. the substance must be prevented from coming in contact with the acid. During the sealing. and is allowed to slide down to the bottom. —After cooling. and heated in the bombfurna. It is convenient to so plan the analysis * that the bombs may be sealed in the evening. In many cases. mark the volume with a file on the outside.c.15 to o. Heating the Tube. first thing the next . Even after the tube is closed. The tube is now sealed in the manner described on page 58. about 0. in accordance with the directions on page 60. If a number of halogen determinations are to be made. made by heating a piece of glass rod in the blast-flame until it softens. and then use this to measure the acid for the different determinations. this is not brought about purposely. it is advisable to measure off 2 c. the weighing-tube is closed by a glass stopper.ee. 53). and then pressing it on a metal surface until a head is formed (Fig.c. of water in a narrow test-tube. care being taken not to touch the walls of the bomb-tube with it. in this case at the beginning of the second day the pressure is reduced by opening the tube.M. To Open and Empty the Tube. From 9-10 the temperature is raised to about ioo°. which is clamped with its open end directed vertically upwards. the gas-tubes being lowered from the furnace. Especial care must be taken before heating the capillary to softening in a . and then in the afternoon opening the capillary. If this has been neglected. an entry is made in the note-book to show which tube lies to the right and which to the left. at first. -*. pressure is developed in the tube. The same method is followed in working with a substance so refractory that several days' heating is required. The heating is done gradually. The heating is begun at 9 o'clock A. If two bombs are heated in the furnace at the same time. therefore. The sealed tube is kept under the hood in the bomb-room. 2500. with a small flame. and the flames increased in size. the danger of the bursting of the tube may be lessened by turning off the gas before leaving the laboratory at noon. io-n „ „ „ *5°°> II-I2 12-3 „ „ „ „ „ „ 2OO°. sealing and heating again to a higher temperature. Gradually these are raised. after it has been standing over night. it must not be removed from the iron case to be examined. and the identity of the two tubes is in doubt. naturally it is most convenient to place the bomb at once in that.The perfectly cooled tube is opened according to the directions given on page 61. over night.ORGANIC ANALYTICAL METHODS ft day. Since in many cases the oxidation begins even at the ordinary temperature. If the furnace is not loaded. The tube is never allowed to remain at the working table. in the iron case. the neglect may be corrected by again weighing the two weighing tubes. The following table will show how the heating of a moderately refractory substance should be regulated. If an especially high pressure is generated by the decomposition of a substance. If a portion of the silver halide adheres firmly to the glass> it may be removed by loosening it with a long glass rod over the end of which has been drawn a piece of rubber tubing (such as is used in the quantitative analysis of inorganic substances) and then washing it out with distilled water. but if it does not. solid lumps. the portion in the tube is diluted with distilled water. and then raised with the fingers and washed several times again. together with the weighing-tube into a beaker by inverting the tube. with distilled water. upon which there is generally obtained a bluish-green solution. The part broken off is first washed free from any liquid or any of the precipitate which may have adhered to it. care being taken that the sudden falling of the weighing-tube does not break the bottom of the beaker. washed thoroughly inside and out with distilled water. this is repeated as often as may be necessary. This is not detrimental to the results of the analysis. Before the conical end is broken off the tube is examined to see whether it still contains crystals or oily drops of the undecomposed substance.78 GENERAL PART large flame. otherwise some of the liquid may easily be spilled. To filter off and weigh the Silver Halide. Since the excess of silver nitrate at times packs together with the silver halide to form thick. to drive back into the tube by gentle heating over a small flame. the precipitate is from time to time crushed . The weighing-tube is removed from the bottom of the beaker with a glass rod or thick platinum wire held against the walls above the liquid. In case it does. this is poured. any of the liquid which may have collected in the capillary. into a beaker. the conical end is removed according to the directions given on page 61. coloured by nitrous acid. After the outer open portion of the tube has been washed with distilled water the tube is revolved and the precipitate in the interior is washed out. — The beaker is now heated on a wire gauze until the silver halide has settled to the bottom and the supernatant Jiquid is clear. the attention should be directed to the open end of the tube and not to the liquid in the rear end. the capillary is again "sealed and the tube reheated. At times the weighing-tube becomes yellow to deep brown in colour due to the formation of silver silicate. In pouring out the tube-contents. the fused residue is moistened. If the substance under examination is silver chloride. the filter. The folded filter may also be incinerated directly in the crucible. It is then treated with a few drops of the corresponding halogen acid. the weight of the ash of which is known. and then evaporated on the water-bath with the halogen acid. it sometimes happens that the silver halide is mixed with fragments of glass. and the temperature increased later . Even after taking the usual precautions. the heating is done only with the outer part of the flame. and the presence . If the analysis is intended to be very exact. and allowed to cool. and transferred to a watch-glass placed on a piece of black glazed paper. cause the percentage of halogen to be too high. In order to convert the silver which has been reduced in the incineration back to the silver halide. with a few drops of nitric acid. as large an amount as possible is separated from the paper carefully. only after complete cooling of the crucible: it is now evaporated to dryness on the water-bath. the principal mass of the silver halide may be moistened before fusion. the end of which has been flattened out to a broad head. which will. which is first heated over a small flame. the heating is continued until the filter ash appears uniformly light. and heated directly over a small flame until it just begins to fuse : the crucible is then placed in a desiccator. the silver halide is collected on a filter. together with the funnel. by the aid of a glass rod. The filter is rolled up tightly. is then dried in an air-bath at 100-1100. and again evaporated to dryness on the water-bath. and washed with hot water until. with a few drops of nitric acid. and not with the inner. no turbidity follows. The portions which fall on the paper are swept into the watch-glass with a small feather. The principal mass of the silver halide on the watch-glass is transferred to the cmcible with the aid of a feather. the funnel being covered with a piece of filter-paper.ORGANIC ANALYTICAL METHODS 79 with a glass rod. reducing part. of course. — if the latter method of incineration has been employed. and ignited in the usual way over a weighed porcelain crucible. on testing the filtrate with hydrochloric acid. After cooling. In order to weigh the dry halide. wrapped with a platinum wire. Agl = 235. and the latter incinerated. AgCl = 143*5.73263 — 1 .96. log-r-^.i .62893 — AgJhJr I == 127. AgBr = 188. l o g . In conclusion.85. AgCl = 143-38.. and glass fragments have been noticed. lo& A g C l = ° ' 3 9 3 3 8 ~ * Br = 80. this is repeated several times. the atomic weights of the halogens as well as the molecular weights of the corresponding silver compounds are here given: I. If the compound under examination is silver bromide or iodide.89. It is then treated with dilute nitric acid. then washing the filter with water. the silver halide is reduced to spongy. log — = 0. it is filtered through a quantitative filter. By careful decantation.= 0. an error may be avoided.0. log — = 0. the liquid is separated from the silver.73273 — II. and precipitating the pure silver chloride in the filtrate by acidifying with hydrochloric acid.78.80 GENERAL PART of glass is noticed in the beaker or on filtering.0. and heated on the water-bath until all the silver is dissolved. (exact): Cl= 3545. The weight of the glass is to be subtracted from the weight of the halide obtained. water is added and decanted. To determine the amount of glass present.0. the undissolved glass fragments are also well washed on the filter. Agl = 243. AgBr= 187. and a small piece of chemically pure zinc is added. metallic silver. moist silver chloride on the filter.0. (approximate) : Cl Cl = 35-5. the analysis is carried out to the end in the usual way. slightly warmed dilute ammonium hydroxide several times. In the course of several hours.= 0.62897 — 1 AgJor I = 126. the silver halide in the crucible is treated with very dilute pure sulphuric acid. l o ^ Cl Br =5 79. It is obvious that the purity of the fused silver chloride may also be tested in this way. After dilution with water. by pouring over the completely washed. and emptying of the tube are performed in exactly the same way as in the halogen determinations. It contains nitrogen over the mercury column. and possesses but two degree marks. diluted with water up to 400 c.c. they are filtered off through a small filter. the capillary is again sealed and the tube reheated. Precipitation of the Barium Sulphate. — The determination of the halogens may be materially facilitated by using 16-20 drops of fuming nitric acid instead of 1-^-2 c. at the suggestion of the author. Heidelberg. but in this case it is evident that the use of silver nitrate is superfluous. depends upon the complete oxidation of the weighed substance. The tube so charged is heate I directly up to 320-340°. Before breaking off the conical end. opening. corrects this defect. the tube is examined to see that no undecomposed portions of the substance are present. The charging. by heating it with fuming nitric acid in a sealed tube.—The liquid from the bomb. Desaga. a solution of barium chloride heated to boiling in a test-tube is gradually added until a precipitate is no longer formed. the column of mercury frequently parts. — it is unnecessary to heat it gradually. QUANTITATIVE DETERMINATION OF SULPHUR CARIUS' METHOD This method. Before the sulphuric acid is precipitated with barium chloride. if there should be. like the preceding one. heating. When an ordinary thermometer is employed to register temperatures above 300°. sealing. A bombthermometer made by C. This can be easily observed by allowing the precipitate to settle somewhat before adding more of the solution. The sulphuric acid thus formed is weighed as barium sulphate.c. Germany.ORGANIC ANALYTICAL METHODS 81 Kiister's Modification. corresponding to 3200 and 3400. The liquid is then heated over a . the bottom of the beaker must be examined for any fragments of glass which may be present. is heated almost to boiling on a wire gauze and acidified with hydrochloric acid. if there are any. — In order to prepare the barium sulphate for weighing. After cooling. Should any barium sulphate adhere to . the liquid is filtered. and to evaporate the liquid ori the water-bath until the acid vapours vanish. the above process is repeated and the second precipitate collected on the filter containing the first. the precipitate remaining in the beaker is boiled several minutes with 100 c. Ignition and "Weighing of the Barium Sulphate. If a precipitate is formed. it may be incinerated while still moist. another beaker is placed under the funnel so that the entire quantity of liquid need not be refiltered. it is for many reasons preferable to wash the contents of the bomb into a porcelain dish instead of a beaker. The precipitate occasionally at first goes through the paper. the percentage of sulphur is too high. the residue is diluted with water. and the operation just described above repeated. without disturbing the precipitate at the bottom. in case it does. With the aid of a small spatula or knife the moist filter is removed from the funnel and folded in the form of a quadrant. Under these conditions. The method just described has the disadvantage that if a smaller quantity of water be used for diluting the contents of the tube than that given above. The precipitate is washed with hot water until a portion of the filtrate tested with dilute sulphuric acid shows no turbidity. which is only removed with difficulty on washing with water. by this operation the nitric acid is removed.82 GENERAL PART small flame until the barium sulphate settles at the bottom of the beaker and the supernatant liquid is perfectly clear: at times from one to two hours' heating may be necessary. before adding the barium chloride. the barium sulphate may easily carry along with it some barium nitrate. Since. from any glass fragments. through a small filter the weight of the ash of which is known. if Bunsen's method is followed. barium chloride is added in order to be sure that a sufficient quantity was used in the first instance. filtered if necessary. Before throwing away the filtrate.c. After evaporating. too much of an excess of barium chloride is to be avoided. water and filtered through the same filter. it is not necessary to dry it before incineration. in consequence of this. For the calcu- . however. the flame increased. under certain conditions. heated a short time with the full flame. and the heating continued until the residue has become white. and the contents of the crucible poured on the filter already used. This source of error may be rectified by treating the ignited barium sulphate with water until the crucible is half full. the greatest portion of the precipitate remaining in the crucible is again treated with water and hydrochloric acid. and that the barium sulphate has carried along some of it. The liquid is filtered from the precipitate through a quantitative filter. after washing repeatedly with water. it is removed with a small piece of filter-paper. and heating on the water-bath for fifteen minutes. which must not be too large at first. is directly under the angle formed by the crucible and cover.ORGANIC ANALYTICAL METHODS 83 the funnel. The cover. it is pressed into the bottom of a weighed platinum crucible. This process is obviously only employed when the barium sulphate has not been evaporated down with sulphuric acid. in the opposite direction.crucible is now placed in an upright position. by the fact that in the precipitation too great an excess of barium chloride has been used. so that the upper half of the opening of the latter is uncovered. which is incinerated with the main mass. the filter and precipitate are again ignited as before. The. the gases formed take fire at the mouth of the crucible. After some time the burner is placed under the bottom of the crucible. If the percentage of sulphur found is too high. does no harm. however. It sometimes happens that on heating the filter. The burner under the crucible is placed in such a position that the flame. this may have been caused. which. This will allow the ignition of the filter to take place at so low a temperature that reduction of the barium sulphate need not be feared. then adding a few drops of concentrated hydrochloric acid. and then allowed to cool in a desiccator. After the filter has been carefully folded toward the centre. also inclined at an angle of 20-30°. It is entirely superfluous to treat the barium sulphate with sulphuric acid and then evaporate it off. is supported before the crucible. placed on a platinum triangle in such a position that its axis is inclined 20-30° from a vertical position. besides the excess of silver nitrate. BaSO4== 233.A . the precipitate filtered off. the purity of which has been tested by adding silver nitrate to it.84 GENERAL PART lation of the analysis the atomic and the molecular weights are given: I. The filtrate thus obtained contains. l o g — — = 0.c. If the barium nitrate solution contains halogen salts as impurities.06. l o g . the sulphuric acid formed by oxidation. (exact) : S = 32. In its place is used a solution of barium nitrate. . BaSO. and the silver halide filtered off after the heating as above described. since the silver as silver chloride would also be thrown down. they may be determined in a single operation by the following method : As in the determination of the halogens the bomb is charged with silver nitrate and nitric acid. and silver nitrate added so long as a precipitate is formed.13779 . and the solution.= 0.13775-1 Simultaneous Determination of the Halogens and Sulphur. This latter cannot be precipitated as before with barium chloride. — If a substance contains both a halogen and sulphur.1 jDaSO II. A large excess of barium nitrate is particularly to be avoided. (approximate) : = 3 2 . which is now free from halogens. it is heated. is used for the precipitation.= 233.46. The precipitation is made hot as above directed. the solution used being as dilute as possible — the volume of which must be at least 500 c. This is made by winding an oblong piece of copper wire gauze spirally around a thin glass rod. a space between the walls and spiral is disadvantageous. long. and not in a glass beaker or flask. both of which are closed by a cork covered with tinfoil. 80-85 cm. the method almost exclusively used for determining nitrogen quantitatively is that of Dumas. in pieces the size of a pea. the nitrogen is evolved as su. It is made of such a width that when in position it will touch the walls of the combustion tube. A copper spiral. long. The dark grains which have become discoloured by impurities are thrown out. about 15 mm. outside diameter.ch. long. it is preserved in a well-closed bottle* . 400 grammes of coarse and 100 grammes of fine cupric oxide. is sifted out in a wire sieve. 3. dish. The former is kept in a large flask. A glass funnel-tube with wide stem (at least 10 mm. The principle involved is that the substance is completely burned by cupric oxide in a tube rilled with carbon dioxide. 2. 7. 5. The fine powder.A combustion tube of difficultly fusible glass. the latter in a small one. 6. in diameter). A solution of 150 grammes of potassium hydroxide in 150 grammes of water. A small flask of pure methyl alcohol (50 grammes) for reducing the copper spiral. which cannot be used. while the carbon and hydrogen are completely oxidised to carbon dioxide and water. It is prepared in a porcelain. since these are frequently broken by the heat generated by the solution. 4.ORGANIC ANALYTICAL METHODS 85 QUANTITATIVE DETERMINATION OP NITROGEN DUMAS' METHOD In scientific laboratories. After cooling. Requisites for the analysis : i. and its volume measured. 10-12 cm. Also a short copper spiral from 1-2 cm. 500 grammes of magnesite. The glass rod is now fused off. A nickel crucible 6 cm. and the heated portion suddenly drawn out to a narrow tube. The sealing is done as follows : The end of the tube is first warmed ih a luminous flame. Besides these. a one-hole rubber stopper for closing one end of the combustion tube. is repeatedly passed through the large luminous flame of a blast-lamp. and the fine copper oxide in the porcelain crucible over a Bunsen flame for a long time. if the tube is not perfectly cylindrical. 10.86 GENERAL PART 8. for the ignition of the coarse cupric oxide. a sieve to sift the copper oxide. the tube rinsed out several times with water. the narrower end being selected for this purpose. and the copper oxide occasionally stirred with a thick wire. A moderately large porcelain crucible for the ignition of the fine cupric oxide. 9. the crucibles being supported on wire triangles. a weighing-tube. and the conical part of the tube just produced is heated and drawn out. it is finally allowed to cool gradually over a small luminous flame. high . thermometer. After complete cooling. the open end of the tube is warmed in a luminous flame. the sharp edges are rounded by the blast-flame: it is then allowed to cool in the luminous flame again. a glass rod fused on it. with constant turning. The cone is then heated in the hottest flame until it falls together. absorption apparatus. A small mortar with a glazed bottom. diameter of top 7 cm. and.. in the blast-flame. a small feather. — The analysis is conveniently begun by heating the entire quantity of coarse copper oxide in the nickel crucible over a large flame (Fletcher burner). and the tube finally dried in one of the two following ways : The tube.\ When this operation is finished. the water allowed to drain off as completely as possible. with constant turning. with constant turning. Preparations for the Analysis. the soot is removed. While the copper is being heated. The covers are placed on the crucibles loosely. and a eudiometer. while a current of air is blown . one end of the combustion tube is sealed to a solid head. it is then heated to softening. the tube may be loosely corked. and the flames may be removed. attached to suction. the substance to be analysed is weighed. since this becomes strongly heated at its upper end. A convenient method is this : The weight of the weighing-flask is determined with exactness to centigrammes. plus substance. are formed. the spiral. A small roll of . The tube is now directly filled with the magnesite until the layer has a height of 10-12 cm. pungent odour (oxidation products of methyl alcohol like formic aldehyde and formic acid).ORGANIC ANALYTICAL METHODS $7 from a blast into the bottom of it by means of a narrower. after a few minutes. Or the combustion tube is clamped in a horizontal position.) tube inserted in the larger tube. (Fig. and dropped as quickly as possible into the test-tube. and the weight of the tube. Filling the Tube. i c. having a sharp. 54). The dark spiral soon assumes a bright metallic lustre. the water vapour is drawn off by the suction. it is clamped in a test-tube holder. The combustion tube is next filled. which frequently become ignited. is determined exactly to the tenth of a milligramme. In the meantime. the copper oxide will have been sufficiently heated. is inserted. To reduce the long copper spiral which is to be used for the reduction of oxides of nitrogen which may be formed. the mouth being at about the level of the table. and the combustion tube equally heated with a Bunsen burner throughout its entire length. or wrapped in a cloth or strips of paper. During the cooling.c. somewhat roaring blast-flame. a narrower tube extending to the sealed end. while vapours. When this operation is ended. longer (10 cm. fastened firmly near the bottom of this is a clamp projecting over the edge of the table supporting the combustion tube in a vertical position. The substance to be analysed is now placed in the weighing-tube. of methyl alcohol is placed . the method of procedure is as follows : Into a test-tube large enough to admit the spiral. and the spiral allowed to cool. the copper oxide has cooled sufficiently to be transferred to the appropriate flask. this weight is entered in the note-book at a convenient place for future use. held by crucible tongs. is then heated to glowing in a large. — At the edge of the working table is placed a stand. this operation is continued until all moisture is removed. is heated for a short time in a Bunsen flame (it need not be reduced) and dropped on the magnesite. or a small brush.88 GENERAL PART copper gauze 1-2 cm. by measuring with the eye. 54. and from the flask coarse copper oxide is poured in until the layer measures 8 cm. layer of the fine.20 gramme is taken. coarse oxide in. The funnel-tube is then placed in the tube. With the aid of a clean. perfectly cooled copper oxide is placed. copper spiral a much of the substance to take. without pressure . unless the substance contains a small proportion of nitrogen. how 2 cm. two are carefully mixed by stirring with the pestle. one can easily decide. and upon this is poured a layer of 2 cm. substance + fine oxide the weight of the empty tube is known as well as that of 2 cm. To the operation following — the mixing of the substance with copper oxide and the transference of the 5 cm. held with pincers or tongs.15-0.. of the fine oxide. clipped feather. Since 10 cm. the contents of the mortar are transferred through 12 cm. standing on black.. fine oxide the substance contained there8 cm. when more is taken.In the bottom of a small mortar. of which 0. free mixture to the tube — especial 10 cm. coarse oxide the weighing-tube the substance to be analysed. such as is used in quantitative operations. during the mixing care must be taken not to stir so rapidly as to cause dust-like particles of the mixture to leave the mortar. and the FIG. magnesite . long. reduced copper spiral care must be given. glazed paper a \ cm. to this is added from 30 cm. Fine copper oxide is now added until the substance is completely covered. as well as the pestle. longer than the furnace . as soon as the tube becomes warmed. being small at first. and placed i n the combustion furnace. The operation must be done cautiously to prevent the light. the burners under the last half of the magnesite are lighted. as well as that of the single layers. and this is likewise transferred t o the tube with the aid of the feather. After opening the pinch-cock of the absorption apparatus. and finally the reduced copper spiral. the magnesite being decomposed by heat as represented in the following equation: MgCOs-MgO + CO* . The length of the tube. In order to protect the latter from the heat. 55). the rear end of which (that under the magnesite) has been raised on a block (Fig. are increased in size. dusty particles from being blown away. — After the tube is filled it is held in a horizontal position and tapped gently on the table in order that a canal may b e formed in the upper portion of the fine copper oxide. is now rinsed with a fresh portion of the fine copper oxide. an asbestos plate having a circular opening in the centre. is regulated in accordance with the size of the combustion furnace. the tube contents are of the same length as the flame surface.ORGANIC ANALYTICAL METHODS 89 the funnel-tube into the combustion tube. there is placed over the portion of the tube projecting beyond the furnace. it is then connected with a rubber stopper to the absorption apparatus which has been charged with caustic potash solution. long. Heating t h e Tube. Generally the tubes are 5 cm. the flames. The following points are to be observed: In the lower part of the absorption apparatus there must be a sufficient amount of mercury to extend almost to the side-tube. of coarse copper oxide. The mortar. In order to raise the temperature higher when it becomes necessary. but not sufficiently t o cause them to meet above the tube. the figures given above refer to a furnace possessing a flame surface of 75 cm. the tube is covered from both sides with the tiles. After about ten minutes a rapid current of carbon dioxide is evolved. more mercury is a d d e d : the end of the glass tube passing through the rubber stopper must be flush with the end of the stopper. if this is not the case. The layer of substance p l u s copper oxide should be about 10 cm. Then follows a layer of 30 cm. GENERAL PART . and the former lowered. after the first warming the heated portions of the tube are covered on both sides with the tiles. until the copper oxide is heated to dull redness. 55. If this is n o t the case. After a rapid current of carbon dioxide has beefh evolved for about fifteen minutes. the pearshaped vessel is raised high enough to cause the caustic potash to ascend somewhat above the tubulure in the glass cock. the end of the delivery tube is dipped under the water in a dish as shown in Fig. An observation will show whether the air has been displaced. and a large air volume collects. so that it contains the principal portion of the caustic potash. Concerning the steps taken in heating the tube.ORGANIC ANALYTICAL METHODS 91 During this operation the glass stop-cock of the absorption apparatus is opened. and the glass cock opened in order that the potash may drive out the air in the delivery t u b e : when this has been done. the flames. which should be t h e case under normal conditions. the burners under the copper spiral are lighted in order to drive out any occluded gas (hydrogen). All the flames but one under the magnesite are now extinguished or lowered. upon which the potash flows in to the lowered pear vessel. the latter is closed. When the air in the tube has been completely replaced b y carbon dioxide. the glass cock is opened. As soon as t h e forward layer. The pear vessel is then raised as high as at first. and those under the long copper spiral as well as those under four-fifths of the adjacent layer of coarse copper oxide are lighted at the same time . only a minimum quantity of light foam should collect over the potash in the course of two minutes. the cock is closed again and the p e a r lowered to the bottom. refer to Fig. As before in heating the magnesite. small at first. and the pear-shaped vessel again lowered as far as possible. If now after two minutes only a trace of foam has collected. the burners under the rear layer of coarse oxide adjacent to . and carbon dioxide is caused to pass through the tube for five minutes longer. 54 — the numbers on the left indicate the portions of the tube t o be heated successively. are increased in size. and the pear-shaped vessel placed as low as possible. the pear raised t o the highest point of the delivery tube. of coarse copper oxide becomes dark red. At this point care is taken that the flames are not so large as to meet above the tube. the glass cock closed. after the tube has become somewhat heated. as at'the beginning of the analysis. all the nitrogen is carried over to the absorption apparatus. in each case. the flames are gradually made larger until finally the tube covered with tiles is heated with full flames. If this is the case. The absorption apparatus is . In this way the burners are gradually lighted from both sides. the cessation of the evolution of the gas. which are increased after a time. As soon as the evolution of carbon dioxide has become active.92 GENERAL PART the magnesite are lighted — small flames at first. the flames under the rear half of the magnesite lighted at the beginning of the analysis are extinguished. toward the middle of the fine oxide. until the generation of the gas is lessened. no other burners are lighted until the evolution of gas ceases. another burner on the opposite side of the fine oxide is lighted. or if they are so large as to occupy almost the entire cross-section of the absorption tube. If the single bubbles cannot be counted. The combustion must be so conducted that the bubbles of gas ascend in the absorption apparatus with a slow regularity. in order that the substance may not yet be burned. thus the substance is regularly and quietly burned. When the gas no longer collects. This is shown by the complete absorption of the gas bubbles by the potash. the tiles being also laid back at the same time if necessary. It is a rule that the heating had better be somewhat too slow than too rapid. small flames are again lighted under the entire layer of magnesite. After a rapid current of carbon dioxide has passed through the tube for ten minutes. Care must be taken that the flames nearest the layer of substance plus fine copper oxide are not too large. For the proper manipulation of this operation especial care must be taken. A small flame is now lighted at the point adjacent to the short layer of coarse oxide : an observation of the absorption apparatus will show whether after some time any unabsorbed gas collects. and increased in size after some time. and the last burners lighted must be extinguished or lowered. the heating is too strong. When this is ended. the tube being covered simultaneously with the tiles. except for a minimum foam-like residue. Upon the operation which now follows— the gradual heating of the fine oxide containing the substance — virtually depends the success of the analysis. and after. the end closed with the thumb. care being taken that in the lower bent portion of the delivery tube no air bubbles are present. Transferring the Nitrogen. During the cooling of the tube the weighing-flask is weighed again. the cock being left open until the delivery tube is completely rilled with the caustic potash. in order that the last portions of carbon dioxide may be absorbed. at an oblique angle. but first one is extinguished. and then after a short time another. as represented in Fig. The flames under the combustion tube are not turned out simultaneously. and so on. the thumb removed and the tube clamped to the cylinder. and the glass cock gradually opened. a thermometer. inverted and dipped below the surface of the FIG. but the pear is raised until the surfaces of the liquid in the pear and that in the tube are at the same level: the apparatus is then allowed to stand for at least half an hour. The eudiometer is now filled with water.ORGANIC ANALYTICAL METHODS 93 then closed by the pinch-cock and the rubber stopper bearing the connecting tube is withdrawn from the combustion tube. held in the clamp which supported the . water. the eudiometer wholly immersed in the water. 56. 56. To obtain the temperature. the end of the delivery tube is dipped under the surface of the water contained in a wide-mouth cylinder. so that the end of the delivery tube may be passed under it. if there are. The gas is not immediately transferred to the eudiometer. — After the nitrogen has stood in contact for at least half an hour with the caustic potash. they must be removed with a capillary pipette. The absorption apparatus is then removed. The nitrogen is thus transferred to the eudiometer. The pear supported by the clamped ring is raised as high as possible above the delivery tube. — and is raised so far out of the water that the level of water inside and outside the tube is the same. After about ten minutes. length of time for various tests. If this. Calculations of the Analysis. then the percentage of nitrogen is p : __ v-{b — w)-o. The actual combustion of the substance requires 30 minutes. or crucible tongs. Total. then the percentage of nitrogen is: s In this formula. the nitrogen has come to the same temperature as the water. is under the same pressure as that indicated by a barometer. v the volume of nitrogen read at the temperature /°. the eudiometer is then seized with a clamp especially adapted to this purpose. w the tension of the water vapour in millimetres at /°. . is g. 15 minutes. The displacement of the last portions of nitrogen by heating the magnesite requires 10 minutes. From the warming of the forward layer of the copper oxide with the spiral to the heating of the rear layer of oxide to a dark red heat. is immersed in the water as far as possible. 5 minutes. The volume of gas thus read off. From the beginning of the heating of the magnesite to the appearance of a rapid current of carbon dioxide requires about xo minutes. and b the height of the barometer in millimetres. 1 hour and 25 minutes. —The following abstract will give an approximate idea of the length of time that the single operations of a well-conducted combustion ought to occupy.i2$6 P~~~ 760-(i -f 0. Length of Time for an Analysis.94 GENERAL PART delivery tube. under the observed conditions. s is the weight of the substance in milligrammes.00367 • t)-s The calculation of the analysis is rendered easier by referring to the table in which the weight of one cubic centimetre of moist nitrogen is given in milligrammes at different temperatures and pressures. the first test as to whether air is still present in the tube follows after a further 15 minutes . — If s is the amount of substance in grammes. — never with the hands. 118 1.096 1.155 1.144 111 .170 1.158 8° "53 9° 1.184 1.097 1.169 1.050 1.171 1.097 1. upon the skill of the experimenter.109 1.062 I.131 1.119 1.146 1.050 "45 1.050 1.090 1.159 738 1.041 1.IIO 1.067 1. 1.047 1.148 111 .127 1.035 13° 14° 15° 16° 17° i8° I9° 20° 21° 22° 23o "35 1.076 1.166 1.053 1.092 1.089 1.142 1.138 -m 1.191 1.079 I-O73 1.142 1.148 10° I-I43 1.070 1.074 1.IIO 1.131 1.067 1.092 1.064 1-059 1-053 1.068 1.123 1. of course.103 1.079 I-O73 1.107 1.075 1.062 1.116 I.076 1.188 1.121 1.163 1.113 1.119 1.096 1.102 1.113 1.047 736 1.081 1.167 1.056 "37 1.136 1.113 1.162 1.062 1.099 1.158 1.098 1.157 1.105 1.128 1.168 1.124 1.121 1.178 734 1.161 1.095 1.118 1.171 1.136 1.152 1. and upon other factors.081 1.149 1.165 1.117 1.147 1.168 1.132 1.150 "33 1.102 1.093 1. WEIGHT OF ONE CUBIC CENTIMETRE OF MOIST NITROGEN IN MILLIGRAMMES.145 1.186 5° 6° l 7° 1.112 1.068 1.155 1.059 i-°53.047 1.126 1.065 1.141 1.100 1.044 1.151 1.in 1.082 1.076 1.056 1.044 "39 "34 1.129 1.160 1.125 1.105 1.153 1.123 1.088 1.085 1.122 1.147 1. 726 1.140 732 1.116 1.156 1.070 1.114 1.120 1.176 1.178 740 1. .104 1.124 1.115 I.064 1.8 1.099 1.152 1.058 1.078 1-073 1. since they depend upon the efficiency of the furnace.181 1.084 1.183 1.084 1.126 1.6 1.106 I.174 1.088 1.166 n° 12° "54 1.059 1-053 24° 25° 26° 27° 28° 29° 30° 1 The values for fractions of degrees and for the height of the barometer not given in the table may be obtained by interpolation.091 1.176 "73 1.082 1.038 73O 1-175 1.^ t b.102 1.163 728 1.179 1.094 1.168 1.085 I-O79 1.070 1.ORGANIC ANALYTICAL METHODS 95 These time figures are.061 1. upon the nature of the substance burned.163 1.091 1.056 1.108 1.086 1.130 1.071 1.158 1.171 1.056 1.150 1.041 "43 "38 "33 1.065 1.129 1.140 1*135 1.IOI 1.164 1.108 1.087 1. only to be considered as approximate. CO CO W •-< CO X^.ON rto O ON ONOO OO 1 COOO COCO CO X^VO vO v o v o O vo Q" X-*vO vO VO vO v o i i .i T^- vo O "^rco N 00 00 t-^vO vO o o o oo rt ON COOO PO vO vo v n ^* Tfco r>-M vo ON o o o o oo ovO r 0 0 OO O O O 0 O o o o oo VO X>OO ON O O O O O O t O» CO f v o o o oo vO X O ONO ^ O . a x>.0 0 N VO N M V O O V> VO VO rjr -*• CO CJ N M M O O O \ O N O O X** N COVO s 00 I * oo vo >-• vo ON co Tj-00 M X N « vo ^ rj.« O O ON ONOO 00 *-» X-^vO VO v o !fr COOO W VO Q N M M o O v o ON coJt-^O ONOO 0 0 t s t s q qqqq N \ O O rhOO ONOO 0 0 X~>vO O O O O O •<*• ON rj.C C O O W N >i O O ? vo O c o NOO 0 0 £>• o OO r>.N Jt>.96 O T}-C\ rj-ON rt* ' CO N N ft >i GENERAL PART \O wvO w \ O O C C N W M »< O O e* tt N N N W 00 CO00 M vO i > t O vo LO 8 O v o O ^ ON rf flrjN N « O O N N N N N N N vo 0 Th O\ rj. w vO CO CO N N M ON cooo c* *>»»-< \O VO VO -*h Tj" VO 0 ^ 0 0 N CO CO N ft ft ^•OO N V O ON •-1 O O 0 O ON T 1 . and may be used again for further analyses as often as desired. all the copper oxide is sifted to separate the coarse from the fine. The magnesite is useless for further analyses. This modification carries with it. In order to replace the air by carbon dioxide. In order to protect the bicarbonate tube from the direct flame. the rear end of the tube is connected with another tube of difficultly fusible glass (closed at one end). a small sulphuric acid wash bottle is interposed between the two tubes. however. General Remarks. The absorption apparatus. wide.ORGANIC ANALYTICAL METHODS 97 Subsequent Operations. The tube is charged as represented in Fig. The layer of bicarbonate is heated with a single Bunsen burner. but the principle is the same in all. which is then well closed. provided that it is reheated each time in the nickel crucible to oxidise it. The tube may also be used again if it has not been distorted by high heating. The substance is placed in a porcelain or copper boat. if a number of nitrogen determinations are to be made. 60 (page 103). it is surrounded by a cylinder of coarse iron gauze (Fig. The bicarbonate may be replaced by a Kipp generator. including the rubber tubing. the disadvantage that the tension of . so that the latter may not be corroded by the caustic potash. The caustic potash in the absorption apparatus. which can be. which is three-fourths filled (in cross section) with sodium bicarbonate. 5 7). In order to absorb the water generated from this on heating. long and 15-20 mm. Further. It is preferred in many places to generate the carbon dioxide from acid sodium carbonate or manganese carbonate. used a second time. is poured into a bottle. Instead of the absorption apparatus of Schiff. — The above-described method of Dumas for nitrogen is used in variously modified forms. A combustion tube open at both ends may be used. described above. the mixing of the substance with the fine copper oxide may be done in the tube. 25-30 cm. beginning at the fused end. — After the tube has cooled and the copper spiral taken out. a graduated tube from which the volume of the gas may be read directly may be used. thus obviating the necessity of transferring it to a eudiometer. is washed out repeatedly with water. Two one-hole rubber stoppers fitting the ends of the combustion tube. carbon dioxide and water. A U-shaped and a straight calcium chloride tube. r Fhe requisites for analysis are : A hard glass tube open at both ends. Two copper spirals of 10 and 12-15 cm. A glass tube provided with a cock. 6. A drying apparatus for air or oxygen. 4. and then wejghing the combustion products. outside diameter 12z 15 mm. 3. A caustic potash apparatus. FIG. respectively. two short spirals 1-2 cm. Four hundred grammes of coarse and 50 grammes of fine : copper oxide. w£th . But as mentioned these modifications do not differ essentially. long. But the copper oxide used for the latter purpose and that for the carbon and hydrogen determinations are always kept in separate bottles. 8. 7.98 GENERAL PART caustic potash is not exactly known. The Geissler form is the most convenient. longer than the furnace. S7- QUANTITATIVE DETERMINATION OF CARBON AND HYDROGEN LIEBIG'S METHOD The essential part of the method consists in completely burning copper oxide a weighed amount of the substance. and therefore a somewhat arbitrary correction must be applied. preserved in bottles closed with tin-foilcovered corks as in the nitrogen determination. 5. 2 . length. It should be about 10 cm. A piece of good rubber tubing 20 cm. but also carbon dioxide. but asbestos or glass-wool. The cork stopper. before the filled tube is used a stream of dry carbon dioxide is passed through it for about two hours. In order to prevent the calcium chloride from falling out. If the nature of the substance to be analysed is such that it is necessary to mix it with fine copper oxide. long (thick-walled and seamless). The two side tubes of the calcium chloride tube are . 61) is filled with granulated. After the tube is filled the open end may be sealed in a blast-flame. dried air is then drawn through for half an hour to displace the carbon dioxide. 10. A screw pinch-cock. which must be freed from any powder by sifting. 12. The open leg is closed by a rubber stopper or a good cork bearing a glass tube bent at a right angle. In order that the tube may be suspended from the arm of the balance in weighing. The coarse copper oxide is not previously heated in the nickel crucible as in the determination of nitrogen. which not only absorb water. 11. are very convenient. and the tube dried by one of the methods given on page 70. thus causing an error in the results of the analysis. After cooling the tube is rinsed out with water several times.ORGANIC ANALYTICAL METHODS 99 9. Preparations for the Analysis. A porcelain and a copper boat. both ends of the tube are provided with loose plugs of cotton. The U-tube for the absorption of the water (Fig. calcium chloride. Two asbestos plates for the protection of the rubber stoppers.is covered with a thin layer of sealing-wax. but this is done later in the tube itself. Calcium chloride often contains basic chlorides. — The sharp edges of the combustion tube are rounded by careful heating in a blast-flame. long. Calcium chloride tubes. a platinum wire with a loop in the centre is attached to both legs. this is allowed to drain off. In this case the plug in this end is not cotton. the latter is ignited for a quarter hour in the porcelain crucible and allowed to cool in a desiccator. six pieces rubber tubing 2 cm. in which the open leg is longer than the other. not fused. After filling the bulbs that part of the tube immersed in the potash solution is cleaned with pieces of rolled-up filter-paper. 3 parts water) as follows : the horizontal tube which is to be charged with solid caustic potash is removed. and this is sucked up with the rubber tubing until the three bulbs are three-fourths filled. is now filled with . 58. removed before filling the bulbs. but it is unnecessary to pass carbon dioxide through this before using. and to the free end of the bulb tube rubber tubing is attached. in which case the water-cock must be opened to a very slight extent. The three bulbs of the potash apparatus similar to the one represented in Fig. in which is inserted a glass rod rounded at both ends. Care must be taken not to suck too strongly. otherwise some of the caustic potash solution may be drawn into the mouth. long. The straight calcium chloride tube is filled in like manner. This may be prevented by inserting an empty wash-bottle between the potash apparatus and the mouth. The inlet tube represented in Fig. long. The tube may be used repeatedly until the calcium chloride begins to liquefy. 58 are three-fourths filled with a solution of caustic potash (2 parts potassium hydroxide. 58 FIG. contained in a shallow dish. i£ cm. or the suction-pump may be used.100 GENERAL PART closed by pieces of rubber tubing 2 cm. The horizontal potash tube. at the left is now dipped into the caustic potash solution. (It may also be heated in an air-bath at 100-no0. In handling the Geissler tubes it is always to be remembered that they are very fragile. one end of which is narrowed.. serves to reduce any oxides of nitrogen. If this is not at hand. To remove the mechanically adhering gas the spiral is placed in a vacuum desiccator. which. but immediately behind the place over which the tubing is to be drawn or pushed. an ordinary desiccator containing a small dish of solid caustic potash or unslaked lime is used. When the apparatus is to be closed by rubber tubing. and in all cases the leverarm formed in lifting them should be as short as possible. it must be refilled. e. as in the nitrogen determination. or a not too thin copper wire is passed through the centre of the spiral and bent at one end to a right angle and at the other in the form of a loop.g. The longer of the two so-called copper oxide spirals need not be reduced before the combustion. it is oxidised in the combustion tube. In order to be able to remove it from the tube conveniently a loop of copper wire is fastened in the meshes of the gauze near the end. as will be pointed out below. it is closed in the same way as the calcium chloride tube. long. after cooling. When the potash apparatus has been used twice. carbon dioxide is passed through it. The shorter spiral. and as soon as the air has been displaced.) For drying the oxygen or air an apparatus consisting of two wash cylinders and two U-shaped glass tubes mounted on a wooden stand is employed. a tube . is next reduced according to the directions given on page 87. it is heated for a few minutes with a Bunsen flame and then allowed to cool in a current of carbon dioxide. then. To remove any adhering organic substances like methyl alcohol or its oxidation products the spiral is placed.ORGANIC ANALYTICAL METHODS IOI coarse-grained soda-lime and solid caustic potash in pea-size pieces as follows: In the bulb is placed a plug of glass-wool or asbestos. a layer of caustic potash. in a glass tube 20 cm. then follows a layer of the soda-lime. and finally another plug of glass-wool or asbestos. The gas passes first through a wash cylinder containing a solution of potassium hydroxide (1:1). it is not grasped by the bulbs. When this is done. on the contrary. mouth of the tube (Fig.. long. Filling the Tube. slow enough to enable one to count the bubbles (the glass stop-cock is opened wide and the current regulated with the pinch-cock). so that on either side of the cock the length is 5 cm. these are gradually increased until finally. The legs of the glass tube containing the stop-cock are fused off and slightly narrowed at the ends. 60). is pushed into the tube 5 cm. assuming that the furnace has a flame surface of 75 cm. from the FIG. and somewhat elastic. at first with flames as small as possible. and finally a wash cylinder containing sulphuric acid (Fig. held in position by another small elastic copper spiral at its upper end. and the latter is connected with the drying apparatus by means of rubber tubing provided with a screw pinch-cock. Igniting the Copper Oxide. the tiles being in position. the entire length of the tube is heated. —The simplest case of combustion with which one can deal is that involving the analysis of a substance containing no nitrogen. —The charged tube is placed in the furnace. while a current of oxygen is passed through the tube. The other end of the tube is allowed to remain open at first. the tube is filled in the following manner: A short copper gauze roll.102 GENERAL PART filled with soda-lime. the end nearest the copper oxide spiral is closed by a rubber stopper bearing the glass stop-cock tube. In a case of this kind. Into the tube lying in a horizontal position the copper oxide spiral is pushed so far that its loop is 5 cm. of sufficient diameter to fit the tube tightly. The water deposited at the beginning of the beating. 59. then one filled with granulated calcium chloride. 59).. and then the opposite side of the tube is partially filled with a layer of coarse copper oxide 45 cm. the copper oxide begins to appear dark red. is now removed . in the forward cool end of the tube. 1-2 cm. copper oxide spiral • 5 cm. free FIG* 60. . coarse oxide Short copper spiral > 10 cm. free . free 15 cm.Short copper spiral 45 cm.5 cm. —While the rear part of the tube is cooling.20 grammes of the substance placed in it and weighed again. the potash bulbs. it is wiped off with a clean cloth. Weighing the Absorption Apparatus and the Substance. if solid. these are replaced. care being taken not to upset the boat. The boat is first weighed empty. which will condense the greater portion of the water. the potash apparatus. are extinguished. after the weighing. it is drawn over the two ends of the glass tubes until they touch. After about 20 or 30 minutes* heating the burners under the copper oxide spiral. is weighed in a porcelain boat which has previously been heated strongly. 0. and at the same time the current of oxygen is cut off. with the cock closed. 61). The straight calcium chloride tube is replaced by the weighed U-tube. and the soda-lime tube of the latter with the straight calcium chloride tube in the same way (Fig. it is then placed on a tin-foil-covered cork. Especial care is taken to have a good joint between the U-calcium chloride tube and the potash bulbs. since at this point very commonly lies the source of error in analyses not concordant. the calcium chloride tube. free from lint.15 to 0. of the copper oxide layer lying next. The Combustion. A thick-walled seamless rubber tubing is employed. in which a suitable groove has been cut. . the copper oxide spiral is withdrawn with a hooked glass rod or wire. Before the absorption apparatus is weighed. and transferred to a desiccator. and cooled in a desiccator. the adjacent empty space. and those under about 5 cm. is then put in position. and the rubber tubing and glass rods removed. The stop-cock tube. The connecting of the different parts of the apparatus may be facilitated by blowing air from the lungs through each rubber joint before pushing it on the glass tubes.104 GENERAL PART with filter paper wrapped around a glass rod. by a rubber joint. the porcelain boat is inserted as far as the coarse copper oxide. with its empty bulb. —When the rear end of the tube is cold. nearest the furnace. and finally the spiral is replaced. To the U-tube is connected. and the substance are weighed. The substance. the front end of the tube is closed by a rubber stopper bearing the straight calcium chloride tube. When no more water collects. with a single small flame. may not be detected. since. If the passage of bubbles becomes too rapid. in consequence of the friction of the solution in the narrow tubes. on the other. a leak. which are increased after some time.ORGANIC ANALYTICAL METHODS IO$ I n order to provide against any possible leak.The rubber stoppers closing the tube may be protected from the heat by placing on t h e tube. taken from the forward highly heated portion of the furnace. If. and on the other. on the one hand. the spiral is brought to a dark red glow. concerning which no satisfactory general directions can be given. A valuable rule is to conduct the heating in such a way that the gas bubbles passing through the potash apparatus follow one another with as slow a regularity as possible. or in the rear. but by covering that portion of the tube containing the boat with hot tiles. With easily volatile substances. viz. the glasscock is opened. Small flames are now lighted under the copper oxide spiral. until. and after a short time. Numerous modifications have been applied to this most difficult part of the analysis. This is conducted in exactly the same way as that given under the nitrogen determination. and a slow current of oxygen (two bubbles per second) is admitted to the tube by carefully opening the pinchcock. then the tube is covered on one side with the tiles. and finally the full flames are used. A test as to whether the apparatus is perfectly tight is not always convincing when the combustion is conducted in an open tube. during the combustion. The heating Is begun. finally. an asbestos plate with a circular hole in the centre. the heating is not constant. the heating at the beginning is not done with the flame. water should condense in the glass-cock. When this is done. Now follows the most difficult operation of the analysis. at first. the gradual heating of the substance. close to the furnace. the flames under the unheated copper oxide are gradually lighted. or several others may be lighted. at times. After closing the screw pinch-cock. two ligatures of thin copper wire or " wax ends " are bound around the joints. this is gradually increased in size. upon which the success of it virtually depends. the heating is moderated. coW . care bsing taken not to allow any flame near the porcelain boat to be too large. it is removed by holding a hot tile under it.1 2 1 ^ . When the boat has been heated some time with the full flames. the water. is also driven over into the calcium chloride tube. The apparatus is taken apart.O496O — I .1 IL (exact) : Percentage of Carbon to =™-<?0***<*> Wt. During this operation. H 2 0 x 202 Wt. the percentage of carbon and hydrogen is found from the following equations: I. o . From the difference in the weights of the absorption apparatus before and after the combustion. the rubber stopper is withdrawn from the front end of the combustion tube.04576. Wt. Percentage of Hydrogen = H2 ^jjr Wt. as it always does in the front end.. as above described. until a glowing splinter held before the opening of the straight calcium chloride tube is ignited.106 GENERAL PART portion of the tube.~ 0 J * Wt. Substance x 11 0. Substance x 18. allowed to stand in the weighing-room for half an hour. the combustion is considered to be ended. condensed for the most part in the front end of the tube. care being taken to prevent the water in the calcium chloride tube from running out To remove the oxygen in the absorption apparatus.. (approximate) : r> 6 r r> x. a slow current of air which need not be dried is drawn through it for 1-2 minutes. a somewhat more rapid current of oxygen is passed through the tube.43573. Substance x 9 TT log g ~ = 0. In order to drive the last portions of carbon dioxide and water from the tube into the absorption apparatus.— : — > Wt. or by heating with a small flame. Wt « C 0 * X 300 Percentage of Carbon = ^7—TTT. and is then weighed.92' = O. HoO x 100 r __ . When this has been done. Percentage of Hydrogen = . with the mouth or suction. closed up as above described. Substance x 11 . the ignition should be conducted throughout with oxygen. The combustion may also be conducted without passing a current of air or oxygen into the tube at the beginning. and not 45 cm. the combustion tube is charged somewhat differently in this case. the combustion proper is performed with the glass-cock closed. As soon as the oxygen is admitted. the combustion is ended. in length. The first copper roll is inserted in the tube.. except that a current of air is used.. In order to prevent the oxidation of the copper. If.. The further operations are the same as those described above.ORGANIC ANALYTICAL METHODS 107 Modifications of the Method. and oxygen is not admitted to the tube until at the end. — In many cases instead of using oxygen for the ignition of the copper oxide. and then burned in the same way in oxygen. the flames under the reduced copper spiral are . Combustion of Substances containing Nitrogen. not 5 cm. The ignition of the copper oxide is conducted exactly as above. the reduced copper spiral serving for the reduction of the oxides of nitrogen mus* be used. Substances which burn with great difficulty can also be mixed with fine copper oxide in a copper boat (see below). it is still necessary toward the end of the operation to pass oxygen through the tube for some time. except that the reduced copper spiral is put in position last—just before connecting the combustion tube with the absorption apparatus. at the end of the operation this is displaced by air. but 15 cm. No change is made in the disposition of the copper oxide spiral. in which case the glass stop-cock is closed. toward the end of the operation the glass stop-cock is opened and a current of air or oxygen passed through the tube. Under these conditions. — Since in the combustion of nitrogenous compounds. The combustion may also be conducted in a current of air. the same result may be obtained by using a current of air. As soon as a glowing splinter held at the end of the straight calcium chloride tube is ignited. the space in front of it being reserved for the reduced spiral. Consequently the layer of coarse copper oxide is but 35 cm.. however. as soon as the substance has been heated for some time with the full flames. but when'the substance is difficult to burn. it is placed upon a sheet of black glazed paper. is used. The sub- . which is absorbed by the potash apparatus along with the carbon dioxide.. a boat made of sheet copper. long layer of lead chromate. 8 cm. Oxygen is not admitted until at the end of the operation. But two points are here to be observed: (i) the lead chromate is not heated as strongly as the copper oxide. nearest the calcium chloride tube (that above about three burners). empty space for boat. since lead sulphate is not completely stable at a red heat. In this case the oxidation is accomplished with granulated lead chromate. giving a result in which the percentage of carbon is too high. difficultly combustible. it is returned to the boat with the aid of a feather or brush. Since the porcelain boats are generally too small to contain a sufficient quantity of this. The gas is passed through until it can be detected at the end of the apparatus as above described. Upon this is carefully spread the weighed substance from a weighing-tube as in the nitrogen determination.— Sulphur compounds cannot be burned with copper oxide in the manner described. then a layer of fine copper oxide is added until the boat is three-fourths full: the substances are now well mixed by careful stirring with a thick platinum wire. is also the same. nitrogenous residue. it is necessary to burn them by mixing with fine copper oxide. The filling of both ends of the tube is done just as described above: copper oxide spiral. long and of a width sufficient to enable it to be just passed into the tube. otherwise it fuses in the glass. etc. is heated very slightly. The ignition in oxygen. Combustion of Substances containing Sulphur or a Halogen. and (2) the most forward portion of the lead chromate layer. It is filled as follows: After it has been previously ignited.108 GENERAL PART extinguished. In the combustion of substances which leave a charred. and half filled with fine copper oxide also previously ignited and afterwards cooled in a desiccator. The combustion is made with the glass-cock closed. since at a red heat the copper sulphate formed gives off sulphurous acid. If some of the mixture should fall upon the glazed paper. but since the copper halides are partially volatile and give up the halogen on being heated to redness. Combustion of Liquids. Halogen compounds can be burned in the usual way with copper oxide. A preliminary trial will show whether the boat containing the empty tube will pass into the combustion tube.ORGANIC ANALYTICAL METHODS 109 stance is mixed in the copper boat with. if it does. and the tube plus substance weighed. ignited lead chromate. If a sufficient quantity is* not obtained t h e first time. 5 3 . the front part of the tube containing the lead chromate is heated but slightly. so. Care must again be taken to prevent any of the liquid from finding its way into the capillary. It is placed in the . only in place of the reduced copper spiral. The tube is filled in the same way as for the combustion of a nitrogen compound. during which operation the tube is not held by the bulb. The rilling is done as follows: The emptytube is weighed. In order to introduce this. To prepare the tube for the combustion. — If the compound to be analysed is a liquid. in which case it will not be necessary to use a silver spiral. the liquid will be drawn up into the bulb. into the tube. Since the lead halides are also somewhat volatile at a red heat. it is placed in the porcelain boat in such a position that the mouth of the tube is directed upwards. the extreme end is filed and broken off. Moderately volatile substances are weighed in a small glass tube which is loosely closed with a glass stopper (see Fig. But it is better to perform the combustion with lead chromate. before it is sealed care must be taken that the capillary contains none of t h e liquid . 62). the operation is repeated. It is now sealed. one of silver is used. Very easily volatile substances are weighed in small bulb-tubes which are sealed after weighing (Fig. it must be removed by heating. provided it is very difficultly volatile. On cooling. and the open end dipped under the liquid t o be analysed. page 76). as above. it can be weighed directly in the porcelain boat. heated gently. due to sudden movements or other causes. powdered. a silver spiral must be inserted in the tube to retain the halogen. 36 = 3 C 2.30-35.72-r.: Carbon =48. eg.98-5-12 =4. is C3H2CL If the numbers obtained in the last division are not integers. If necessary. The simplest formula thus obtained from the analytical data does not always correspond with the true molecular weight. the results being 5. . therefore. This must be determined by one of the usual methods..HO GENERAL PART boat with its open end elevated and directed toward the front end of the furnace.08-1. the following numbers have been found.30% the percentage figures are divided by the corresponding atomic weights. r 2 .1.36 : 4.98% Hydrogen = 2. e. Calculation of the Atomic Formula. — In order to calculate the simplest formula "of a substance from the figures giving its percentage composition.36=1 Cl The simplest atomic formula. they are multiplied by the smallest integer which will convert the fractions into whole numbers.36= 2 H 1.72% Chlorine =48.36-^1.72 H 48. If. unless it may be inferred from the nature of the reaction by which the substance analysed was produced. the capillary is shortened. the method is as follows: If a substance contains. and 2.36 Cl These figures are divided by the smallest— in this case 1. The precaution to ascertain beforehand whether the boat loaded with the tube will pass into the combustion tube.g.5 = 1. 7.08 C 2.72 -=.5» I-75> a^d °-5> they are multiplied by 4.t = 2. There is thus obtained: 48. should always be taken. 00 These figures are taken from the report of the Atomic Weight Committee of the German Chemical Society.06 Cl= Br= I = O= 3545 79.OO 14.ORGANIC ANALYTICAL METHODS III The exact atomic weights of the elements used in analytical calculations are: H= I. .85 16.96 126.OI C = N= S = I2.04 32. the flask being heated on a small sand-bath with a large flame (Fig. the contents of the receiver should be drawn up into the con2 J-1857. An upright coil condenser (see Fig. Since the boiling-point of ethyl bromide is low (3&0). The mixture is subjected to distillation. 63). After cooling the mixture to the room temperature. which must not be too slow. page 345). 63. the receiver is filled with a sufficient amount of water containing a few pieces of ice^o allow the end of the adapter to dip under the surface. page 34) may be employed advantageously.441. REACTION: THE REPLACEMENT OP AN ALCOHOLIC HYDROXYL GROUP BY A HALOGEN I. c . If. during the distillation.SPECIAL PART I. add quickly with constant shaking. and then 100 grammes of finely pulverised potassium bromide (see Hydrobromic Acid. with a quite rapid current of water passing through it. the cooling being continued. add carefully 75 grammes of ice-water. ALIPHATIC SERIES 1. 112 . 27. long condenser. 90 grammes of alcohol (about 9 5 % ) . a FIG. The reaction is ended as soon as the oily drops which sink to the bottom of the receiver cease passing over. ) of concentrated sulphuric acid contained in a round litre-flask. At the beginning of the operation. without cooling. EXAMPLE: Ethyl Bromide from Ethyl Alcohol1 To 200 grammes ( n o c . is used. being observed. so that air may enter it. but always in thick-walled. The same result may be attained by turning the adapter to one side. 70-80 grammes. I . and finally distilled. For the preparation of ethyl benzene (which see) the ethyl bromide thus purified cannot be used. contained in a small flask of about 200 ex. The acid containing the dissolved ether is then run off (in a separating funnel) from the ethyl bromide. added drop by drop and with frequent shaking. and finally with a dilute solution of sodium carbonate. the free flame is not used for the heating. 126. 250. The ethyl bromide distils between 35-400. it is never allowed to stand in open vessels for any length of time . The finished preparation. dried with calcium chloride. If it be desired to prevent this. until it separates out in a layer under the ethyl bromide. is treated. during which the flask must not be closed. In consequence of" the low boiling-point of ethyl bromide. The ethyl bromide thus obtained is contaminated with a small amount of ether. contained in a flask surrounded by a freezing mixture of ice and salt. the well-cooled crude ethyl bromide. In this case. dried with calcium chloride. EXAMPLE: Ethyl Iodide from Ethyl Alcohol1 To a mixture of 5 grammes of red phosphorus and 40 grammes of absolute alcohol. capacity. so-called specimen bottles. before drying with calcium chloride. during the drying over calcium chloride. the same precautions as to cooling. 2. The lower layer is then run out of a separating funnel. the flask must be closed by a tight-fitting cork. Yield. the main portion at 38-390. with concentrated sulphuric acid. 50 grammes of finely pulverised iodine are added gradu1 A. The lower layer of the distillate consisting of ethyl bromide is washed in the receiver several times with water. mentioned above. and redistilled as before.ALIPHATIC SERIES 113 denser. must not be preserved in thinwalled vessels of any kind. which is shaken up several times with ice water. particularly at summer temperature. this difficulty may be overcome by placing the receiver in such a position that the end of the adapter reaches just below the surface of the water. but the bulb of the fractionating flask is immersed in a vessel filled with water at 60-700 (compare page 22). about 50 grammes. Hydrobromic acid reacts with greater difficulty. the flask is frequently shaken during the addition. The first reaction takes place most easily with hydriodic acid. eg. it is poured through a funnel containing some asbestos or glass-wool into the fractionating flask. and cooled from time to time by immersion in cold water. the colourless oil is now separated in a dropping funnel. e. in many cases saturation with the gaseous acid being sufficient to induce the reaction. The boiling-point of ethyl iodide is 720.g. The distillate.1 + P(OH) S (PCI* PBr3) 1. the flask is dried and heated for a short time with a luminous flame kept in constant motion. a reflux condenser being attached to the flask. Should the last portions go over with difficulty. and distilled. This may be effected in two ways: (1) by causing the alcohol to react with the halogen hydracid as in the preparation of ethyl bromide. The distillation is facilitated by the use of a frayed thread (see page 34). Br (HCI. to remove the iodine. is washed several times with water to free it from alcohol. coloured brown by iodine. The ethyl iodide is then distilled off conveniently by immersing the flask in a rapidly boiling water-bath. and then with water to which a few drops of caustic soda have been added. the mixture is heated for two hours on the water-bath. An air condenser — a straight vertical glass tube is the common form—is connected with the flask.: the replacement of an alcoholic hydroxyl group with a halogen atom. HI) (2) by treating the alcohol with a phosphorus halide. and the reaction mixture is allowed to stand at least four hours. Yield. it is . [OH + Hl Br = H2O + C 2 H 5 . (In case the experiment was begun late in the afternoon. it may stand until the next day.) In order to complete the reaction. Both of these reactions are special cases of a reaction of general application. If the calcium chloride should float on the oil.: C2H5. OH + PI3 = 3 C2H5. dried with a small quantity of granular calcium chloride. viz. as in the preparation of ethyl iodide. the water-bath is removed.SPECIAL PART ally in the course of a quarter hour. : 3 C2H5. Br Trimethylene bromide +2H 2 O Hydriodic acid. in this case. the quantity of the halogen acid. but. to heat in a closed vessel under pressure.OH CHo. With di-acid and poly-acid alcohols the reaction takes place.OH CH2.Br + 2 HBr =CH 2 CH2.OH CH2 CH2. acts upon the poly-acid alcohols in a different manner. Hydrochloric acid reacts with most difficulty. the number of hydroxyl groups which are replaced by the halogen depends upon the conditions of the experiment...g.ALIPHATIC SERIES 115 frequently necessary to heat the alcohol saturated with the acid in a sealed tube. necessary to employ a dehydrating agent — zinc chloride is the best — or with the alcohols of high molecular weights. it can in some cases. in the preparation of methyl chloride and ethyl chloride. in consequence of its reducing properties. OH + HC1 = CGH5.OH CHo.. e. is replaced by iodine. e&? . etc.: C6H5.CHo. CH2C1 + H2O Benzyl alcohol Benzyl chloride But phenol hydroxyl groups cannot be replaced by the action of a halogen hydracid. like the one given. .Br I + HBr = I + H2O CH2. but also to the aromatic alcohols. This reaction is not only applicable to the aliphatic.OH +2HCI =CHC1 CH2.g. The above method for the preparation of ethyl bromide is a simple case of the general reaction.g. In place of using hydrobromic acid directly. be generated by warming a mixture of potassium bromide and sulphuric acid: KBr + H. and it is.OH +2H 2 O CH. CH 2 . e. A single hydroxyl group.OH Glycerol CH2C1 Dichlorhydrine CH2. at least with hydrochloric and hydrobromic acids.SO4 = HBr + KHSO4.OH Trimethylene glycol CH2. while at times other hydroxyl groups are replaced by the hydrogen of the acid. the temperature.OH Ethylene glycol Ethylene bromhydrine CH. e. and that particular one in combination with a carbon atom which is in turn in ^combination with other carbon atoms. CH2C1 + POC13 + HC1 Trichlorhydrine This example illustrates the more energetic action of the phosphorus halide as compared with the corresponding hydrogen halide. COOH + 2 H2O 2.CH(0H). CH2C1 + 2 POC13 + 2 HC1 Ethylene glycol Ethylene chloride (£) CH 2 (OH) . CH 2 (OH) + 2 PC1S = CH2C1. CH2(OH) + 11 HI = CH3.: (a) CH 2 (OH) .Il6 SPECIAL PART <k CH 2 . in many cases it is better to generate the phosphorus halides in the course of the reaction. (c) CH 3 . OH. as well as the first. giving rise to an acid-chloride: . COOH + HI = CH 2 I. COOH + 2 HC1 = CH2C1. CHC1. CH(OH). This is not always necessary.CHC1 . CHI. especially when a phosphorus halide which has been previously made is used.COOH + PC15 = CH3. e.CHI.g. The second reaction takes place much more energetically. CH3 + 4H 2 O + 61 #-Sec. or as above.CH2. . CHC1. replacing it with the halogen.CH3 + 6H2O + ioI «-Sec. CH(OH).g. CH(OH). CHC1. CH2(OH) + 7 HI Erythrite Glycerol Isopropyl iodide = CH 3 .CH 2 . due to the fact that the phosphorus halide also acts upon the hydroxyl of the carboxyl group.CH(0H). CH 2 . CH(OH). This reaction. e.CH2. CH 2 .COOH + POC13 + HC1 a-Hydroxyproprionic acid a-Chlorproprionic add In cases of this kind a complication arises. is applicable to poly-acid alcohols and substituted alcohols. at least in introducing bromine and iodine. CH2C1 -f PCI5 Dichlorhydrine = CH2C1. Hexyl iodide With derivatives of alcohols. it is impossible to replace the third hydroxyl group of glycerol with chlorine by the use of hydrochloric acid. by adding to the mixture of alcohol and red phosphorus either bromine from a dropping funnel. alcohol-acids (hydroxy acids) the first reaction takes place: CH 2 . COOH + H2O jS-Hydroxyproprionic acid Glyceric acid • 0-Iodoproprionic acid a-jS-Dichlorproprionic acid CH 2 (OH).OH O H •+ CH 3 1 CH 3 3 CH. CH(OH).CH2. Butyl iodide Mannite CH 2 (0H). finely pulverised iodine.OH 2 CH2(OH).CH(OH). The monohalogen alkyls CnH(2n+i) Cl(Br. which are gaseous at the ordinary temperature. CO. ether. like cetyl iodide. NOH < 2< /OH Picric acid /NO2 + PC15 = C 6 H 4 < + POCI3 NCI /Cl +PC1 5 = C6H2<( PC1 = C6H2<( HC1 \NO2)3 \(NO 2 ) + POCl3-hHCl Picryl chloride But the quantities obtained are much less satisfactory. takes place. the reason being that the phosphorus oxychloride attacks the unacted-upon phenol. especially under the influence of light. as mentioned above. The halogen alkyls mix readily with organic solvents. and the members of the series having high molecular weights. carbon disulphide. so-called molecular silver is added to the liquid. is impossible with the halogen hydracids. CHC1. This decomposition can be prevented if some finely divided.Cl + H2O = CH.CO. CO. Cl + POCI3 + HC1 (Br) /NO2 C6H4<.OH + HC1 The action of phosphorus iodide on poly-acid alcohols is similar to the action of hydriodic acid referred to under Reaction 1. The more energetic action of the phosphorus halides may also be perceived in the fact that phenol hydroxyl groups can be replaced by a halogen. a slight decomposition. which becomes brownish red after a long time. (OCSH5)3+ 3 HC1 In this way a large portion of the phenol is withdrawn from the main reaction. as alcohol. CHC1. OH + PC15 = CH 3 .OH = PO. OH + PC15 Phenol (Br) = C6H5. forming phosphoric acid esters. the exceptions being methyl and ethyl chlorides and methyl bromide.CO. e. A coloured iodide can be made colourless by shaking it with some caustic soda solution. . C16H33I.CHC1. which are semi-solid.CHCl.: C6H5. by the use of the phosphorus compounds. e. on long standing.: POC13 + 3 C6H5. resulting in the separation of iodine. The iodides are only colourless when freshly prepared. I) are in most cases colourless liquids.g. salve-like substances.g. imparting to them a faint pink colour at first. Cl + POC13 + H O The acid may be regenerated by treating the acid-chloride with water: CH3.. which.ALIPHATIC SERIES 117 CH 3 . the bromides and iodides heavier than water.g. This property decreases in all three classes with the decrease in halogen percentage from the lower up to the higher members of the series.g. they are used primarily as a means of introducing alkyl groups into other molecules. to replace in an alcohol. i. mercaptan. or (COOH)-group by an alkyl radical. it presents a method of preparing the higher members of a series from the lower. C2H5 + Nal C6H5. (SH)-. Various examples of this will be taken up later in labor* .NH 2 + 2 CH3C1 = C B H. etc. 'c 6 H s .. better the silver salt. Since under these conditions another radical is introduced into the molecule. i. SNa + IC2H5 = C2H5.and tri-methyl amine are also formed at the same time. the corresponding bromides boil about 250. simpler ones. and the iodides 500 higher. If it is desired. or in case of acids.CH 8 + HI Methyl amine Di.e.. e. S. the latter have the highest specific gravities. C2U6 + Agl Silver acetate The alkyl groups may be introduced into the ammonia molecule and into organic amine molecules by means of the halogen alkyls. the higher molecular weight compounds have a smaller specific gravity than the lower members. to prepare an ether of these substances. The chlorides are lighter.Il8 SPECIAL PART benzene. e.0. e. by means of the halogen alkyls.g. ONa + IC2H5 = C 2 H 5 . is treated with the halogen alkyl. C2H5 + Nal Sodium alcoholatc Sodium ethyl mercaptide Sodium phenolate • Ethyl ether Ethyl sulphide Phenyl methyl ether = Anisol Ethyl acetate C 2 H 5 . or acid the hydrogen of the (OH)-. but not with water. Aniline Dimethyl aniline Hydrogen atoms in combination with carbon may also be replaced by alkyl radicals.e. i.. by replacing an hydrogen atom with an alkyl group. COOAg + IC2H5 = CH 3 .0. phenol.e.N(CH 8 ) ? + 2 HC1. ONa + ICH3 = C 6 H 5 . The chlorides have the lowest boiling-points. CH 3 + Nal CH 3 . COO. the corresponding sodium compound. The ease with which the monohalogen alkyls react with other compounds gives them great importance.: C2H5.: NH 3 + ICH 3 = NH 2 . ALIPHATIC SERIES II9 atory practice.CHI. e.CH3 + HOH = CH 3 .g. the isopropyl iodide is most simply obtained from glycerol and hydriodic acid. As above mentioned. Here it will be sufficient to refer to several equations showing this kind of reaction. is a case of this kind. CH3. e.CH(OH) . C2H6 + IC2H5 = S Ethyl sulphide g% Triethylsulphine iodide . COOC2H6+ICH3 = CH3.C2H5 + Nal COOC2H5 Ethyl malonic ester Q H 8 + C1C2H5 Benzene (In presence of A1C18) = C 6 H 5 . so that by this reaction the glycerol can be converted into the isopropyl alcohol (compare Reaction 13). CH .CH = CH2 + HI Isopropyl iodide Propylene In many cases the alcohols may also be prepared from the halogen alkyls. CHNa. the halogen alkyls serve for the preparation of the unsaturated hydrocarbons of the ethylene series. C 2 H S + HC1 Ethyl benzene Fittig's Synthesis. by which a halogen atom is replaced by an alkyl group. as is the case in the example given.COOC2H5 + Nal Sodium acetacetic ester | CH.: CH3. C2H5 + 2 NaBr Brom benzene * Ethyl benzene Further.g. like sulphides and tertiary animes : C2H5. CH 3 .CH 3 + HI Isopropyl alcohol This reaction is obviously only of importance when the halogen alkyl is not obtained from the corresponding alcohol. CO. to be taken up later. S.CHI. CO. Methylacetacetic ester COOC2H6 CHNa COOC2H5 Sodium malonic ester COOC2H5 + IC2H5 = CH . Halogen alkyls also unite directly with other compounds.CH3 = CH3.: C6H5Br + BrC2H5 + 2 Na = C6H5. and for many other compounds. According to this conception. the solutions of these contain the undissociated molecules.e. so that this reagent does not serve in the usual way to show the presence of a halogen. bromide.1 It has been customary to explain this by saying that the affinity between the halogen atom and carbon is greater than that between the halogen and the metallic atom. e. Not the least trace of silver bromide is formed.g. for the preparation of the phosphines. substances which are dissociated in water solution..I2 o ( 3 SPECIAL PART ) 8 Trimethyl amine Tetramethyl ammonium chloride . K and Cl. The organic halides are non+ — electrolytes. gives an abundant precipitate of silver iodide. the molecule KC1 is dissociated into its ions.e. zinc alkyls.of silver nitrate with a few drops of ethyl bromide. they are also used for the preparation of the* metallic alkyls.N. while in case of the brom alkyls. bromide.ICH3 Methylpyridine iodide Pyridinc With these examples the list of the many-sided reactions of the halogen alkyls is not exhausted. at once.g. i. EXPERIMENT : Treat a solution . Only halogen ions react. * 1 A noteworthy exception Is ethyl iodide. potassium chloride. the potassium chloride reacts with silver nitrate. Finally. or iodide respectively. . attention is called to the characteristic difference between the organic and inorganic halides. According to our later views the difference between the two classes of compounds is explained thus: The metallic halides belong to the class of so-called electrolytes. i. because no further separation of the potassium from the chlorine (other than that effected by solution) is necessary. e. e. While. or iodide in solution act instantly with a silver nitrate solution to form a quantitative precipitate of silver chloride. which when shaken with a water solution of silver nitrate. ICH8 = C3H. quantitatively with the silver ions of silver nitrate.. the brom-carbon union must first be severed.g. Methyl iodide does not react with silver nitrate. silver nitrate in a water solution does not act on most organic halides. the mixture is heated on a rapidly boiling water-bath until nothing more passes over. 87. 8o grammes of phosphorus trichloride are added through a dropping runnel. the distillate 1 A. lighter layer.ALIPHATIC SERIES 121 2. and the heating continued until the active evolution of hydrochloric acid gas slackens. Since acetyl chloride is very easily decomposed by moisture. mersed in a porcelain dish filled with water at a temperature of 40-500. from the heavier layer of phosphorous acid.63. 64. the flask being cooled by water. The bulb is then im- FIG. and the liquid which was homogeneous before heating has separated into two layers. . REACTION: PREPARATION OP AN ACID-CHLORIDE PROM THE ACID EXAMPLE : Acetyl Chloride from Acetic Acidx To ioo grammes of glacial acetic acid contained in a fractionating flask connected with a condenser (coil condenser). To separate the acetyl chloride which forms the upper. For complete purification. If an acid does not react too energetically. e. except that the dropping funnel is replaced by a thermometer.. Phosphorus oxychloride is employed in rare cases. similar to the one employed above 'for the substitution of an alcoholic hydroxyl group by a halogen. . therefore. In order to replace the hydroxyl of a carboxyl group (CO. but the condenser-tube must be tightly connected with a tubulated flask (suction flask). since the reactions involved in the methods described under (2).122 SPECIAL PART must not be collected in an open receiver. there is formed an acid-chloride. the acid-chlorides are almost always prepared by the action of phosphorus tri. Yield. X. on the sodium or potassium salt. page 21. may be used. this is selected in preference to the more energetic pentachloride. page 116. a mixture of an acid and phosphoric anhydride is treated with gaseous hydrochloric acid (heating if necessary). 17.C1 + H2O This reaction is without practical importance.CO. In practice. Boiling-point of pure acetyl chloride.OH) by chlorine.OH + HC1 = X. The reaction probably takes place in accordance with the following equation: In cases in which the boiling-point of the acid-chloride desired does not lie far from that of phosphorus oxychloride (no 0 ). the distillate is distilled in a similar apparatus. 51 0 . 80-90 grammes. and. may be used for' the redistillation. 64.or penta-chloride on the acid directly. the reaction being analogous to that by which ethyl bromide was prepared. The above reaction is mentioned here only because it throws some light on one of the methods used in esterification. If. If. the trichloride is always used. The portion distilling from 50-56° is collected in a separate vessel. The selection of the chloride of phosphorus depends upon (1) the ease with which the acid under examination reacts. as in the case of acetic acid and its homologues. thus rendering a fractional distillation for the separation of the products difficult.CO. protected from the air by a calcium chloride tube. which will be briefly described below under the characteristics of the acid-chlorides.g. as represented in Fig. are exclusively used. take place much more smoothly and easily. and (2) upon the boiling-point of the acid-chloride. a reaction. the trichloride of phosphorus reacts easily with the formation of the acidtchloride. The apparatus represented in Fig. or in many cases. C O . OH + PC15 = CflH5. CO. colourless crystalline substances. for an instant. ONa + PC15 = 3 CH 3 . benzene. phosphorus oxychloride. the replacement of hydroxyl by chlorine usually causes a lowering of the boiling-point. Cl + POC1S + HC1 Benzoic acid Benzoyl chloride Attention is called to the fact that for one molecule of phosphorus pentachloride. since they unite with the moisture and decompose. They fume in the air. there is formed. three molecules of the acid-chloride are obtained. The boilingpoints of the acid-chlorides are lower than those of the acids. + HC1 Caprylic acid C 6 H 5 . but one molecule of the acid-chloride is obtained. = C7H15. but the higher members are more conveniently distilled in a vacuum.CO. . CO. the higher.OH « 1180 Q H . OH + PCI. The lower members of the series of acid-chlorides are colourless liquids. They are heavier than water. at ordinary pressure without decomposition. with the use of one molecule of phosphorus pentachloride. CO. Cl + POOL.ALIPHATIC SERIES 123 as is the case with the higher members of the acetic acid series with the pentachloride. this is used. CO. CO. If the pentachloride is allowed to act on a soctium salt. and while this no longer acts upon the free acid. CO. upon which it acts as indicated by tl equation: 2 CH 3 . the latter is used exclusively. thus forming the corresponding acid and hydrochloric acid. it can convert two other molecules of the salt into the chloride: 3 CH 3 . the trichloride and oxychloride react with great difficulty: C7H15. The phosphorus oxychloride is used generally only when dealir with the salts of carbonic acids. carbon disulphide. They boil. CO. generally. but are easily soluble in indifferent organic solvents like ether.CO.C l Boiling-point 199° '«" 250° CH 3 . O H The acid-chlorides possess pungent odours. as above. CH. ONa + POCI3 = 2 CH 3 . With the aromatic acids. . Cl + NaPO a + NaCl This reaction may be used with advantage in order to utilise more of chlorine of the phosphorus pentachloride than is the case when the latter acts upon the free acids. and do not mix with it.C1 Boiling-point 51© | Q H ^ C O .CO. since.. Cl + NaPO a + 2 NaCl In this way. This decomposition takes place often with extreme ease. >the analogous transformation of an acid-chloride takes place with far greater ease. On shaking the tube. With the lower members. the chlorine atom is united to the acid radical much less firmly than it is in the case of an alkyl radical. In other cases. observed for a short time. sinking to the bottom. CO. Cl + C 6 H 5 . in many cases. an energetic reaction sets in with evolution of heat. OC2H5 + HC1 Ethyl acetate CH 3 . and continues with violent energy. the reaction begins almost instantly at the ordinary temperature. or potassium hydroxide. The non-volatile residue can be used. benzoyl chloride.g. acetyl chloride. of acetyl chloride.. in order to convert a halogen alkyl into an alcohol. without further purification. The acid-chlorides react with alcohols and phenols to form esters: CH 3 . OH = CH 3 . often with the addition of sodium hydroxide. and the chloride passes into solution.c. e. to boil it a long time with wa£er. a carbonate or acetate. OH = CH 3 .. from the volatile phosphorus oxychloride formed when phosphorus pentachloride is used. OH + HC1. Cl + C2H5.124 SPECIAL PART To separate the chlorides from the by-products formed by the phosphorus chloride. CH 3 . CO. Cl + H2O = CH 3 .g. by distilling off the volatile chloride from the non-volatile phosphorus acid. While it is generally necessary. which will be prepared later. which happens immediately if the water is not cold. it may be obtained perfectly pure by distilling it in a vacuum. the oily drops. do not mix with it. the mixture is heated in a vacuum apparatus on an actively boiling water-bath. but it is necessary to heat the higher members to induce the transformation. CO. CO. upon which the phosphorus oxychloride passes over. OC0H5 + HC1 Phenol Phenyl acetate . a fractional distillation is made. and may be . EXPERIMENT : To 5 c. CO . of water in a test-tube is gradually added \ c. in case it distils without decomposition. CO. — The acid-chlorides are decomposed by water th the formation of the corresponding acid and hydrochloric acid. e.c. Chemical Reactions. If the water is very cold. either on a water-bath or over a free flame. In order to separate a chloride. one can proceed as in the case of acetyl chloride. drop by d r o p . Cl + NH 8 Aniline = CH S . concerning the importance of which more will be said later.c.ONa = C H v C O . CO. as just described. Acctamidc Acctanilide CH 3 . If the compound reacts readily with an acid-chloride. NH 2 + HC1. This will cause the ethyl acetate to separate out. add an equal volume of acetyl chloride. The addition of anhydrous sodium acetate often materially assists the reaction. of aniline.l .^ as in ethers. the tube being cooled as before. There is probably formed. For the preparation of an ester.Cl + CH 8 . CH 3 + HC1 EXPERIMENT : To i c. e. C O . finely pulverised salt is added until no more will dissolve. reacts with the alcohol. O .5.g.ALIPHATIC SERIES 12$ EXPERIMENT : To i c. CO. of alcohol in a test-tube. The acid-chlorides react with ammonia as well as with primary and secondary organic bases with great ease: CH 3 . this mixture is then treated with an equal volume of water. the previously prepared chloride is rarely used. Finally. it contains either alcoholic or phenol hydroxyl. or in order to detect them. Acid-chlorides act upon the salts of carbonic acids. an energetic reaction takes place with a hissing sound. NH 2 = C6H. However. the method of procedure being to pass gaseous hydrochloric acid into a mixture of the corresponding acid and alcohol to saturation. do not react with acid-chlorides. since compounds containing oxygen in some other form of combination. the action of the acid-chlorides upon alcohols and phenols is made use of to separate the latter from solution. the liquid is then carefully made weakly alkaline with sodium hydroxide. forming anhydrides : CH 3 . CO. Cl + CfJH5. cooled with water. C H 3 . an intermediate acid-chloride which. N H . CO. from the carbonic and hydrochloric acids.N a a Acetic anhydride The next preparation will deal with this reaction. acetyl chloride is added in drops.c. The acid-chlorides are also used to determine whether a substance under examination contains an alcoholic or a phenol hydroxyl group or not.CO.CO. benzoyl chloride is most generally used for this purpose. . If the pleasant-smelling ethyl acetate does not separate out on the water solution in a mobile layer. CO. by a melting-point determination. the Friedel-Crafts ketone synthesis is particularly mentioned. /CH 3 /CH 3 CH3. as well as for that of ketones. and recrystallised from hot water. The fact that hydrogen in combination with carbon can be replaced by an acid radical by the use of an acid-chloride is of special importance. The precipitate is filtered off.C1 + Zn<( = C H 3 . or. the quantity of which is increased by rubbing the walls of the test-tube with a glass rod. Melting-point. in regard to the details. and five times its volume of water is added. this reaction may be employed to decide whether a given base is. especially of liquid bases. upon which an abundant precipitate of acetanilide separates out.i26 SPECIAL PART which ceases when about the same volume of the chloride is added. tertiary.C1 = C 6 H 5 . This reaction is also used to characterise organic bases by converting them into their best crystallised acid derivatives. The reaction is indicated by the following equation: C6H6 + CH3. reference must be made to larger works. 1150. in practice. The mixture is cooled with water. This will be taken up later. and in order to detect small quantities. on the other.CH s Acetone . Since the tertiary bases do not react with acid-chlorides. The final reactions will only be indicated here.CO. primary or secondary. C ^ C H 3 + ZnO \CH8 \ Zinc methyl Trimethyl carbinol / C H3 \ C H3 =2CH 3 .CH 3 + HC1 Benzene (In presence of A1CIS) Acetophenone The acid-chlorides are also of service for the synthesis of tertiary alcohols (Butlerow's Synthesis). because they no longer contain any ammonia hydrogen. In this connection.CO.CO. on the one hand. 2 An upright coil condenser may be used. The second half is then allowed to run in. Yield. Boiling-point of acetic anhydride.ALIPHATIC SERIES 127 3 . 17) with the addition of 3 grammes of finely pulverised anhydrous sodium acetate. in order that the pasty mass may be stirred up with a glass rod. this is poured back into the funnel and again allowed to act on the sodium acetate. and the anhydride distilled off from the salt residue by means of a luminous flame which is kept in constant motion. The distillate is finally purified by distilling in an apparatus similar to the one used in the rectification of the acetyl chloride (see also Fig. except that the fractionating flask is replaced by a tubulated retort (Fig. and the mass solidifies as soon as 1 A. As soon as the first half of the chloride is added. which serves to convert the last portions of acetyl chloride into the anhydride. In order to dehydrate it is placed in a shallow iron or nickel dish and heated over a free flame (120 grammes for this experiment). on further heating steam is copiously evolved. anhydrous sodium acetate (for the preparation of this. in which case an adapter is unnecessary. page 128). the reaction is interrupted for a short time. The salt first melts in the water of crystallisation. The separating funnel is then removed. about 50 grammes. REACTION: PREPARATION OP AN ANHYDRIDE FROM THE ACIDCHLORIDE AND THE SODIUM SALT OF THE ACID EXAMPLE : Acetic Anhydride from Acetyl Chloride and Sodium Acetate1 For the preparation of acetic anhydride an apparatus similar to that used in the preparation of acetyl chloride is employed. 50 grammes of acetyl chloride are added drop by drop from a separating funnel.2 To 70 grammes of finely pulverised. If in consequence of a too rapid addition of acetyl chloride some of it should distil over into the receiver undecomposed. Preparation of Anhydrous Sodium Acetate: Crystallised sodium acetate contains three molecules of water of crystallisation. 87. . 138°. the tubulure closed with a cork. 65. 149. see below) contained in the retort. Cl + CH 3 . After cooling. 65. provided the flame is not too large. in case this should happen. the fact will be recognised by the evolution of combustible gases and . and the anhydride of the acid may be made by treating its chloride with the corresponding sodium salt. The reaction of acetyl chloride with sodium acetate takes place in accordance with the following equation: CHoCCX CH3. the mass is now heated with a large flame.CO. FIG. containing two different .128 SPECIAL PART the main portion of the water has been driven off. the salt is removed from the dish with a knife. the charring of the substance. the burner being constantly moved. until the solidified mass melts for the second time. In order to remove the last portions of the water. ONa = >O + NaCl CH3CCK This reaction is capable of general application.CO . since when it is kept for a long time it always takes up water. it is recommended that this also be melted once. The so-called mixed anhydrides. Care must be taken not to overheat. If commercial anhydrous sodium acetate is at hand. CO\ >0 + H. by using the chloride and sodium salt of two different acids: CH3. the higher members.C0. as stated.They possess a sharp odour.CO\. but the higher members must be distilled in a vacuum. Cl + PO3Na + NaCl 2 C H .0 = 2 CHo.c. ONa + POCI3 = 2 CH 3 .Cl = 2 >0 + 2NaCl CH3.CH-CH 3 . C 0 . and phenols.CH 2 . but soluble in indifferent organic solvents. • 4 CH 3 . of water are treated with % c. are insoluble in water. n 8°. is wholly analogous to that of the chlorides . alcohols.CO/ Since...CO/ CH 8 .C(K ^ CH 3 .CO/ EXPERIMENT : 5 c. The boiling-points are higher than those of the corresponding acids: Acetic acid.Na + 3 NaCl CH 3 . CO. 0 N a + 2CH.CCK CHo. it is better to allow the same to act directly on an excess of the salt. can also be prepared by this reaction. K . but the anhydrides react with more difficulty than the chlorides.ALIPHATIC SERIES 129 acid radicals. . the anhydrides yield the corresponding acids: CH3. The chemical conduct of anhydrides toward water. as well as bases. 1380. The lower members can be distilled without decomposition at ordinary pressure. it is not necessary for the preparation of an anhydride to first isolate the chloride.CO/ The lower members of the acid-anhydride series are colourless liquids. Thus with water.CO. It will be recalled that the corresponding chloride reacts instantly with water very energetically. ONa + POC13 = 2 >O + PO.CH2. of acetic anhydride. • The latter sinks to the bottom and does not dissolve even on long shaking. CO.ONa= >0 -f-NaCl CH3. crystallisable solids.CO.OH CH 3 .c. CO. so that from the oxychloride and salt an anhydride is directly obtained: 2 CH 3 . Acetic anhydride. solution takes place. an acid-chloride may be obtained from an alkali salt of the acid and phosphorus oxychloride. Their specific gravities are greater than that of water. If the mixture be warmed.CO. COv >O = CH3.NH2 + ">O = C 6 H 5 . CO.CO.CH 3 + CH3.. — acetylating. and heated gently for several minutes. Anhydrides of high molecular weight react with water with still greater difficulty. With alcohols and phenols.CO\ C6H5. If it does not separate from the liquid.c.OH = CH3. of alcohol are added to 1 ex. OC6H5 + CH3.CO/ EXPERIMENT : Mix 5 c.CO.c.NH. of water with •£ c.OH CH«. OH CH 3 . while the acid-chlorides react at the ordinary temperature: CH3. without warming. — since it passes over into the acid. and add a little caustic soda solution.OC2H5 + CH3.CO\ )O + C6H5. It is then treated with water and carefully made slightly alkaline. CO/ NH3 + .CO/ CH 3 . The acetic ester can be recognised by its characteristic pleasant odour. C O / Phenyl acetate It is to be noted that one of the two acid radicals in the anhydride is not available for the purpose of introducing the acetyl group into other compounds.CO/ CH3. of acetic anhydride in a test-tube.CO X _ >O + 2NaOH = 2CH3. solution takes place much more readily with the formation of the alkali salts: CH 3 .c. With ammonia and primary or secondary organic bases. it may be treated with common salt. NH2 + CH8. CO. On shaking. and require a longer heating to convert them into the corresponding acid.ONa + CH.CCK >O + C2H.I3O SPECIAL PART In the presence of alkalies. EXPERIMENT : 2 c.OH CH 8 . the anhydrides react like the chlorides : CH3. CO. OH = CH8.CO.CO. of acetic anhydride. . solution takes place. OH CH 3 . the anhydrides form acid-esters on heating. CO.CO. as in the experiment on page 125. therefore. and may be recrystallised from a little hot water. which have been previously warmed in a flame.c. add twice the volume of water. it may be mentioned briefly that they yield alcohols. heat to incipient ebullition.CCX )O + H2 = CH3. therefore. The viscous mass is warmed on an actively boiling water-bath to 80-900.CO.979. After the portions of substance adhering to the upper end of the tube have been removed by melting down carefully with a flame.c.CHO + CH3. finely pulverised ammonium carbonate is added (100 grammes will be necessary) until a testportion diluted in a watch-glass with water just shows an alkaline reaction.CHO + H 2 = CH 3 . and the intermediate aldehydes when treated with sodium amalgam: CH3.CO/ Aldehyde CH3. the last traces are removed with filter-paper. until a few drops of it diluted with water just show an acid reaction. of aniline to 1 c. like the chlorides. phenols. after cooling. In order to complete the enumeration of the reactions of the acidanhydrides. and detection of alcohols. these are filtered off. of acetic anhydride. characterisation. and amines. 4. separation. 15. it is then poured (without the use of a funnel-tube) directly into two wide bomb-tubes of hard glass. The acid-anhydrides can. for the recognition.CH 2 . be used.OH . A single Volhard tube (see page 63) is much more convenient.ALIPHATIC SERIES EXPERIMENT : Add 1 c. possible to pass from the anhydride of an acid to its aldehyde or alcohol. and then. . the tube sealed and heated 1 B. OH CH3. It is. REACTION: PREPARATION OP AN ACID-AMIDE PROM THE AMMONIUM SALT OF THE ACID EXAMPLE: Acetamide from Ammonium Acetate1 To 75 grammes of glacial acetic acid heated to 40-50° in a porcelain dish on a water-bath. The crystals of acetanilide separate out easily if the walls of the vessel be rubbed with a glass rod. NH 2 Ammonium oxalate Oxamide . and then crystallised from ether. the reaction-mixture may be fractionated. The fraction passing over between 180-230° is collected in a beaker. can also be readily obtained by this method. at which point the acetamide begins to distil. a portion of the distilled amide is again pressed out on a drying plate. this is not the odour of pure acetamide. The reaction involved in the preparation of an amide from the ammonium salt of the acid is capable of general application. and the walls are rubbed with a sharp-edged glass rod. cooled by ice water at the end of the distillation. There is first obtained a fraction boiling between 100-130°.g. The liquid reaction product is fractionated under the hood in a distilling-flask provided with a condenser. but of an impurity accompanying it. '••£"•• CO. Substituted acid-amides. about 40 grammes. COOH3N. and especially easily substituted aromatic amides. it may be purified by filtering off the impurities and crystallising. There are thus obtained colourless. ONH4 = CH3. by heating a mixture of the acid and amine a long time in an open vessel: CH 3 . NH2 + H2O In order to purify the amide thus obtained. or more conveniently. or if the amide separates out in a solid condition. The temperature then rises rapidly to 180° (an extension tube is substituted for the condenser. the crystals separating out are pressed on a drying plate to remove the liquid impurities.NHo I =| +2H 2 O CO.H5 + H2O Aniline acetate Acetanilide T h e ammonium salts of di. CO.ONH4 CO.a n d poly-basic acids react in a similar way. CO. e. NH . The latter is subjected to dry distillation.ONH4 CO. heated in a sealed tube at 220-2300 for five hours : CH3. CO. The product thus obtained possesses an odour very characteristic of mouse excrement. In order to remove the impurity. Yield. C(. odourless crystals. By another distillation of the pressed-out crystals. C6H5 = CH 3 . see page 22). melting at 82°. acetanilide. consisting essentially of acetic acid and water.132 SPECIAL PART for five hours in a bomb-furnace at 220-230°. the almost pure acetamide boiling at 223° passes over. as in the case of acetamide. colourless. One of the amido-hydrogen atoms possesses acid properties in that it may be replaced by metals. they must be regarded as acids rather than bases. CO. by boiling the solution of the amide with mercuric oxide: .NH 2 CH3. NH 2 + C 2 H 5 . It is true that a salt corresponding to ammonium chloride — CH 3 . OH Ethyl acetate CH 3 . but this shows a strong acid reaction. so that the acid-amides possess only a very slight basic character.CO.CO. as will be discussed more fully under methylamine. „ 213 0 While the entrance of an alkyl residue Into the ammonia molecule does not change the basic character of the compound. crystallisable compounds. and (2).ALIPHATIC SERIES 133 Concerning further methods of preparation. CN + H2O = CH 3 . primary or secondary bases form acid-amides very easily: CH3.g.NH 2 CH 3 .CO. until finally they become insoluble.C(X >O + NH 3 ==CH 3 . CO • NH 2 -t HgO = ( C H r CQ . CO.NH 2 (aliquid). the solubility decreases with the increase of molecular weight. with the exception of the lowest member. and decomposes easily into its components.HC1—» can be prepared from acetamide by the action of hydrochloric acid. Boiling-point. 141° Proprionamide. CO.. the entrance of a negative acid radical enfeebles the basic properties of the ammonia residue. The boiling-points of the amides are much higher than those of the acids: Acetic acid.CO. by treating a nitrile with water: CH 3 . formamide.CO/ The acid-amides may be furthermore obtained by two methods of general application: (1). is unstable. NH 3 Acetonitrile The acid-amides are. it may be stated that acid-chlorides or anhydrides when treated with ammonia. Boiling-point.CO. Acetamide.NH 2 . The mercury salts of the acid-amides may be prepared with especial ease. the lower members being very easily soluble in water.Cl + NH 3 ==CH 3 . „ 118 0 223 0 Proprionicacid. OC2Hj + NH 3 = CH 3 . by treating an ethereal salt with ammonia. 2 CH 3 . H. acetamide. e. If it is desired to assign to the acid-amides a definite character. CN + H2O Acetonitrile The same result is obtained by treating it with phosphorus pentachloride. it is converted into a nitrile: CH 3 . the amide-chlorides or imide-chlorides are formed: CH 3 . The latter goes into solution. on being warmed with alkalies. CO. NHC1 CH 3 . NHBr CH 3 . In the acid-amides. CO. i. more rapidly by warming with alkalies: CH 3 .g. this is shown by the fact that they are saponified. OH + NH 3 EXPERIMENT : Heat some acetamide in a test-tube with caustic soda solution. If an acid-amide is treated with a dehydrating agent. The amido-hydrogen atoms can also be replaced by the negative chlorine and bromine atoms. decomposed into the acid and ammonia. CC12. CO. NH 2 + POC13 Amide-chloride The very unstable amide-chloride then passes over. CO. NH 2 + H2O = CH 3 . NBr2 Acetchloramide Acetbromamide Acctdibromamide The monohalogen substituted amides are of especial interest. phosphorus pentoxide. in the presence of an alkali: CH 3 . CH 3 . e.H2O = CH 3 . CO. CN 4. into the more stable imide-chloride: CH 3 . as well as by the positive metallic atoms. but in this case the intermediate products. while the solution contains sodium acetate. CO. with the loss of one molecule of hydrochloric acid. on boiling with water. NH 2 = CH 3 . An intensely ammoniacal odour is given off. CC1-NH = CH. NHBr 4. NH 2 4. CO. the acid radical is not firmly united with the ammonia residue. NH 2 + HBr + CO2 This important reaction will be taken up later.e..134 SPECIAL PART EXPERIMENT : Some acetamide is dissolved in water.H Q . they yield primary alkylamines: CH 3 .PC15 = CH 3 .. These substitution compounds are obtained by treating the amide with chlorine or bromine. NH2 = CH 3 . CC12. CO. under the preparation of methyl amine from acetamide. treated with a little yellow mercuric oxide. and warmed. since. and the salt of the formula given above is formed. CClz: NH + HC1 Imide-chloride And this finally into the nitrile. 820. contained in a small. the acetonitrile is then distilled over with a large luminous flame. e.ALIPHATIC SERIES 135 5.CN + KI CH9.CO NH 2 = CH 3 . The distillate is treated with half its volume of water. ammonium acetate heated with phosphoric anhydride: CH 3 . in a single operation the nitrile may be obtained directly from the ammonium salt. and then solid.CN jEthylene cyanide 1 A. it loses water. 10 grammes of dry acetamide are added. kept in constant motion. 64. pentasulphide. If an acid-amide is heated with a dehydrAig agent (phosphorus pentoxide. REACTION: PREPARATION OP AN ACID-NITRILE FROM AN ACID-AMIDE EXAMPLE : Acetonitrile from Acetamidel To 15 grammes of phosphoric anhydride. about 5 grammes. if it is treated with a powerful dehydrating agent. e. the flask is connected with a short condenser. dry flask. : CH3. The reaction proceeds with much foaming. After the two substances are shaken well together. COONH* = CH 3 .CEEN + H 2 O Acetonitrile Since. or pentachloride). with a not too large luminous flame kept in constant motion.g. into the receiver (test-tube). The upper layer is removed with a capillary pipette and distilled.. the acid-amide may be made by dehydrating the ammonium salt of an acid. After the mixture has been heated a few minutes. chlorides) with alcoholic potassium cyanide: = CH3. 332. and then heated carefully.g. Boiling-point. CN + 2 H2O The acid-nitriles may also be obtained by heating alkyl iodides (or bromides.CN 2KCN= I " +2KBr CH 2 . . potash is added until it is no longer dissolved by the lower layer of liquid. and passes over into the nitrile. Yield. as has just been done. a small amount of phosphoric anhydride being placed in the fractionating flask for the complete dehydration of the nitrile. thus. CH 2 .: CH 3 .CN = Proprionitrile = Ethyl cyanide etc.CH 2 . The lower members of the nitrile series are colourless liquids.g. COONH4 which immediately reacts with the alkali or acid.NH 2 On heating with acids or alkalies. primary amines are formed (Mendius1 reaction) : 1 CH 3 .CN + 2 H 2 = CH S . they take up two molecules of water. and pass over into the ammonium salt as an intermediate product: CH3. etc.COOK + NH 3 + H2O CH3. in accordance with the following equations: CH3. crystallisable solids.I36 SPECIAL PART C6HS.NH 2 Ethyl amine l A. from zinc and sulphuric acid) be allowed to act on nitriles. 129.SO4 5 4 )K Ethyl potassium sulphate Proprionitrile These two reactions differ from those above in that the introduction of a new atom of carbon is brought about. the solubility in water decreases with the increase in molecular weights. CH 2 ." If nascent hydrogen (e. If they are heated with water up to 1800 under pressure.COONH4 + KOH = CH3 . e. they take up one molecule of water and are converted into the aciftmides: CH 3 . . CN = Acetonitrile = Methyl cyanide C2H5. therefore. may be equally well designated as cyanides. CN + K.COONH4 4.CO. etc.CN + H2O = CH 3 . and.g. Cl + KCN = C 6 H 5 .CN + 2 H2O = CH 3 . The nitriles thus appear to be cyanides of the alkyls.HC1 = CH 3 . iaj. CN + KC1 Benzyl chloride Benzyl cyanide or by the dry distillation of alkyl alkali sulphates with potassium cyanide: O|C2H5 CN|K + = c 9 H 5 . the higher members.COOH + NH4C1 This process is called " saponification. when this temperature is reached. CS. the upper layer is filtered through a dry folded filter. CN + CH3.c. distils over. containing a mixture of 50 c.CO\ >O = N(CO.35°- . is closed by a two-hole cork. REACTION: PREPARATION OF AN ACID-ESTER PROM THE ACID AND ALCOHOL p EXAMPLE : Acetic Ester from Acetic Acid and Ethyl Alcohol1 A ^-litre flask.CCX >NH = Diacetamide CH3. of concentrated sulphuric acid. formed in the reaction. of glacial acetic acid is gradually added through the funnel.CO/ = 3 X CHg. CN + CH 3 .c. In order to remove the acetic acid carried over.c. NH 2 Thioacetamide CH 3 . CO.ALIPHATIC SERIES 137 Further. the distillate is treated in an open vessel with a dilute solution of sodium carbonate until the upper layer will not redden blue litmus paper. but of less importance. The mixture is heated in an oil-bath to 140 0 (thermometer in oil). through the other a glass delivery tube connected with a long condenser or coil condenser. through one hole passes a dropping funnel. of alcohol and 400 c. OH = CH 3 . The layers are now separated with a dropping funnel.CN + NH 2 .OH Hydroxylamine NH 2 Acetamide-oxime CH 3 XN + HC1 =CI Imide-chloride 6. CN + H2S = CH3. of alcohol and 50 c.CO/ CH3. general reactions may be indicated y the following equations: CH3. at the same rate at which the ethyl acetate (acetic ester). and shaken up with a solution of ioq 1 BL 33. CH3)3 = Triacetamide CH 3 .c. a mixture of 400 c. the upper one dried with granular calcium chloride and then distilled on the water-bath (see page 16). OH = CH 3 . sulphuric acid being frequently used for this purpose in the preparation of acid-esters. O A g + IC 2 H 5 =CH 3 . Cl + C 2 H 5 . carried out practically on the small scale in the foregoing preparations. Acid-esters can be obtained directly by the action of acids on alcohols: I. as soon as a certain quantity of the ester is formed. (3) / ° + C 2 H 5 • OH = CH 3 . OC2H5 + CH 3 . the previously prepared chloride was not used. where the salts of organic acids are more readily obtained than the free acids. OC2H5 + HC1 It will be remembered that. There are several methods by the use of which this condition may be changed. CO. CH 8 . OH + C 2 H 5 . in which an equal number of molecules of the ester are formed. the latter saponifies the ester. and the corresponding quantity of water.CO. Boilingpoint. according to equation II. OC2H5 + H2O A reaction of this kind never takes place to any degree in quantitative proportions. The two layers are again separated with the funnel.OC 2 H 5 + AgI (2) CH 3 . accordingly a dehydrating agent is added to the mixture. Other methods for the preparation of acid-esters have been referred to. about 80-90% of the theory. in these reactions.. 3252).. so that at this point it is only necessary to recall the equations: (1) C H 3 X O . C O / . In many cases. but that hydrochloric acid was conducted into a mixture of the acid and alcohol (see acetyl chloride). 7 8°. or the acid was heated with alcoholic hydrochloric acid (see B. CO. OH = CH 3 . and. in order to remove the alcohol.OH + C 2 H 5 . according to equation I. CO.OH In such cases. in accordance with the following equation: II. CO. in part. at the same time. and decomposed.OC 2 H 5 + H2O = CH3. CO . OH CH 3 . The saponifying action of the water must be neutralised. Yield. CO.CO. since. a condition of equilibrium is reached. they may be used for the preparation of the esters by heating them directly with alcohol and sulphuric acid. 28.CO. CH 3 .138 SPECIAL PART grammes of calcium chloride in ioo grammes of water. CO. fruit-like odours. the higher members. The action of ammonia upon acidesters.CO.CO. C2H5. in case an ester is moderately soluble in water. OH. A. OC2H5 + KOH = CH 3 . that the crude reaction-product is shaken with a sodium carbonate solution until the ester no longer shows an acid reaction.OC 2 H S CH3. the esters are saponified by heating with water: CH 3 . CO. CO. OC2HS + NH 8 = CH 3 . contained in a flask provided with a delivery tube and an inverted 1R. the entrance of more complex alkyl residues raises the boiling-points: CH 3 . 102. CO. CO. OH + C2H5. has already been referred to under acetamide: CH 3 . The lower members of the series of acid-esters are colourless liquids with pleasant. as well as those of the aromatic acids. it is better to use a solution of calcium chloride. 7. OH Other methods of saponification will be further discussed when a practical example is taken up. OH The saponification is effected more readily by heating with alkalies: CH 3 . REACTION: SUBSTITUTION OP HYDROGEN BY CHLORINE EXAMPLE : Monochloracetic Acid from Acetic Acid and Chlorinex A current of dry chlorine is passed into a mixture of 150 grammes of glacial acetic acid and 12 grammes of red phosphorus. forming acid-amides. OC2H5 + H2O = CH 3 . C3H7) are lower than those of the corresponding acids. CO.OH CH 3 . CO. The alcohol may be removed from esters difficultly soluble in water by repeatedly washing with water.ALIPHATIC SERIES 139 Concerning the purification of the acid-esters. OK + C 2 H 5 . .OC 6 H 13 Hexyl acetate Boiling-point.CO. 57 0 " " 78 0 " " 1180 « " 1690 As already mentioned. NH 2 + C2H5. as ethyl acetate. The boiling-points of esters containing alkyl residues of small molecular weights (CHg. are crystallisable compounds.OCH 3 CH 3 . 23.222. it may be mentioned. this is united with the main quantity.g. In summer the chlorination may require a single day. the flask is heated on a rapidly boiling water-bath. Chlorine or bromine substitution products of aliphatic carbonic acids can be obtained by the direct action of the halogen on the acids: CH3. while during the cloudy days of winter. Boiling-point. the operation is conducted in direct sunlight. which is again distilled. The suction must not be continued too long. and there is obtained a second portion of monochloracetic acid. This is treated as before (cooling and filtering). CO. care must be taken in handling it. because the monochloracetic acid gradually becomes liquid in warm air. The reaction is assisted more effectively by adding a so-called " carrier. Since monochloracetic acid. two days may be necessary. this is cooled in ice-water and the walls rubbed with a glass rod. attacks the skin with great violence.'! Iodine . e. The portion solidifying. The product thus obtained is perfectly pure. the loose crystals being pressed together with a spatula or mortar-pestle. It may be essentially facilitated by certain conditions. and the portion passing over between i7o-2oo°is collected in a separate vessel. The fraction passing over from 150-2000 is collected in a separate beaker. The filtrate is again distilled. 1860. The reaction is ended when a small test-portion cooled with ice-water solidifies on rubbing the walls of the vessel (test-tube) with a glass rod. especially when warm. OH + HC1 L (Br2) (Br) (HBr) If the reaction is allowed to continue for a long time. Yield varying. But the action of chlorine or bromine on acids is very sluggish.I4O SPECIAL PART condenser. consisting of pure monochloracetic acid is rapidly filtered with suction. If. For the separation of the monochloracetic acid the reaction-product is fractionated from a distilling flask connected with a long air condenser. CO. OH + C > = CHOC1. The best result is obtained by performing the reaction in the direct sunlight. since the success of the chlorination depends essentially on the action of the sun's rays. and must be placed in such a position as to receive as much light as possible. 80-125 grammes. the reaction proceeds much more rapidly than in a dark place.. other substitution products can also be obtained. as well as anhydrides.COA . Direct experiments have shown that acid-chlorides. CO.CO. The disadvantage necessarily incident to the use of iodine as a carrier is. phosphorus pentachloride is first formed from the phosphorus and chlorine. OH + HI The chlorine acts upon the hydriodic acid as follows: (3) HI + Cls = IC1 + HC1 The molecule of chlorine iodide is thus formed anew (equation 1) and can chlorinate another molecule of acetic acid. according to the following reaction: (2) CH 3 . chlorine iodide is formed: (1) Cl + I = IC1 This acts.OH= >O + HC1 CH 8 .CO. it causes the substitution to take place more rapidly and completely. with an excess of the acid. and this latter. and so on. as a chlorinating agent in the second phase. The continuous action of this carrier depends upon the following facts: In the first phase of the reaction. — in small quantities.C1 + CH S . The action of the iodine in the last case depends upon the fact that the molecule of chlorine iodide (1C1) is more easily decomposed into its atoms than the molecule of chlorine (Cl2). Since a small amount of phosphorus is sufficient for the chlorination of a large amount of acetic acid. OH + IC1 = CH2C1. In an entirely different way the chlorination is facilitated by the addition of red phosphorus. generates acetyl chloride. this. it is true. in this fact the action of red phosphorus finds its explanation. then. When added in small quantities to the substance to be substituted.ALIPHATIC SERIES I4I may be used as such for the introduction of chlorine or bromine. CO.CO.Cl + POCI3 + HC1 CH.CO. forms the anhydride. In accordance with the above statements. In this case. the question as to how this is continuously effected remains to be answered. that the reactionproduct is easily contaminated with iodine derivatives. the following reactions take place: (1) P + C15 = PC15 (2) CH 3 . acting on the acetic acid.CO\ (3) CH S .OH + PC15 = CH3. are substituted by chlorine with much greater ease than the corresponding acids.. CH 2 .OH + KI = CH2I. Iodine cannot be introduced directly into aliphatic acids like chlorine and bromine.OH + CH3. in trim ethyl-acetic acid (CH 3 ) S . Thus.CO. reacting on the add. since it first forms sulphur chloride.. bromination will not take place. 2216.C. As a substitute for red phosphorus. sulphur is also recommended for the chlorination of aliphatic acids. 4.OH.brominated. but also as a means for determining constitution.1726.CO/ CH3. OH a-Bromproprionic (5) CH2C1. To obtain iodine substitution products.g. which. B. 14. monochloracetic anhydride is formed: CH3Cl. CHBr. . 20.C(X + HC1 = CH2C1 .COv >O + C1 2= >O + HC1 CH. The ability of (a) an add to form a bromine substitution product can. like phosphorus chloride. be used as a test for the presence of an a-hydrogen atom.O CH3. in part l B. converts it into an acid-chloride. This acts in a wholly similar manner.1 The halogen atoms always enter the a-position to • the carboxyl group..142 SPECIAL PART If the chlorine now acts on the anhydride. A. CHBr.CO/ But this reacts directly with the hydrochloric acid. CO. The other phases of the reaction are similar to those given above. B. first formed in reaction 2. e. 21.CO. B. 24a. which is utilised repeatedly by its regeneration in accordance with reactions 3. OH a-Brombutyric acid If no a-hydrogen atom is present. 1904. 24.CO.CO. 21.. 141.CO. and 5. Cl > CH3. the molecule of acetyl chloride. CO. in accordance with this equation: W (4) CH 3 . is also conducted with the addition of red phosphorus (Hell-Volhard-Zelinsky Method). they yield: CH S . therefore. 2026. The bromination of aliphatic carbonic acids. it is necessary to treat the corresponding chlorine or bromine compound with potassium iodide: CH2C1. which is not only of great importance in preparation work. 891.CO . OS There is thus obtained. besides the molecule of chloracetic acid.OH + KC1 The halogen derivatives of the fatty adds are in part liquids. when proprionic and butyric acids are. e.g. 14.OH + Ag0 = I 2 CEL CO.ALIPHATIC SERIES 143 solids.OH CO. OH + H2O = CH 2 (OH). 1. . OH + NH 3 = CH 2 .CO. on the other hand/the halogen alkyIs. through one hole passes a dropping funnel.133. through the other a glass delivery tube connected with a long condenser. REACTION: OXIDATION OP A PRIMARY ALCOHOL TO AN ALDEHYDE EXAMPLE : Acetaldehyde from Ethyl Alcohol* A i-j-litre flask containing n o grammes of concentrated sulphuric acid and 200 grammes of water is closed by a two-hole cork. for the synthesis of polybasic acids. esters. To the lower end of the condenser is attached an adapter bent downwards.NH 2 .CO. OH + HC1 Oxyacetic acid = Glycolic acid CH2C1. chlorides. since jfhey form salts. OH Acrylic acid Cyanacetic acid CH2C1. CO.329. Below are given a few equations capable of general application: CH2C1.OH + KCN=CH2.CN.and amido-acids. the narrower portion of which passes through a cork in 1 A. OH + HC1 Amide-acetic acid = Glycocoll CH2I CH2 + KOH COOH CH2 = C H + KI + H2O CO.C OH Succinic Acid +2AgBr 8..\ In th^ir reactions they resemble the acids. CO.1853. They are of great value in the preparation of oxy. on the one hand. CO. anhydrides. CO . of unsaturated acids. etc. etc.CO.OH CH2 2CH2Br. is connected with a moderately large reflux condenser. the reaction is assisted by heating with a small flame. Since the aldehyde cannot be obtained easily from the reactionproducts by fractional distillation. (See Fig. If uncondensed vapours of the aldehyde escape from the receiver. The suction flask is placed in a water-bath filled with a freezing mixture of ice and salt. on proper treatment. to the flask more slowly. 65. above the surface of the liquid in the flask. until boiling begins. water. the lower end of which is about 3 cm. which. After all of the mixture has been added. 66. On the other hand. of dried ether. During the addition of the mixture.) By using an upright coil condenser connected directly with the suction flask. an adapter is unnecessary.144 SPECIAL PART the neck of a thick-walled suction flask of about |—litre capacity. since the heat produced by the reaction is sufficient to cause ebullition. readily yields the pure aldehyde. the mixture is admitted FIG. and acetal. a solution of 200 grammes of sodium dichromate in 200 grammes of water which has been treated with 100 grammes of alcohol is then added in a small stream through the dropping funnel. if boiling is not caused by the flowing in of the mixture. placed on a wire gauze.c. The aldehyde thus formed distils into the receiver. the flask is heated for a short time by a flame. The larger flask is heated over a wire gauze until the water just begins to boil. it will be unnecessary to heat the flask. After the condenser has been filled with water at . page 128. which is connected with two wash-bottles. The apparatus for this purpose is arranged as follows: A* small flask to contain the aldehyde. each containing 50 c. it is first converted into aldehyde-ammonia. besides some alcohol. Into the upper end of the condenser is placed a cork bearing a ^-shaped glass tube. but at present the more soluble and cheaper sodium salt (1 part dissolves in 3 parts of water) is employed wherever it is possible. Since aldehyde has a low boiling-point (21 0 ). of extracting two hydrogen atoms from a primary alcohol by oxidation. As an oxidising agent in the above case. until the liquid smells strongly of it. Yield. into the ethereal solution contained in a beaker surrounded by a freezing mixture of ice and salt. the aldehydeammonia which has separated out is scraped from the sides of the vessel and adapter with a spatula or knife. washed with a little ether. the crude aldehyde is heated for 5-10 minutes to gentle boiling. chromic acid is the most suitable in the form of potassium. the receiver is connected with the condenser by a cork. and is absorbed by the ether. After an hour. about 30 grammes. To obtain aldehyde-ammonia. or sodium dichromate in the presence of sulphuric acid: Na2Cr207 + 4 H2SO4 = O3 + (SO4)3Cr2 + Na2SO4 + 4 H2O The rather difficultly soluble potassium dichromate (1 part dissolves in 10 parts water) was formerly generally used. Aldehydes can be obtained by the use of the general reaction. the flame must be somewhat increased immediately.OH + O = CH 3 . In order to obtain pure aldehyde. and then allowed to dry on filter-paper in a desiccator. filtered with suction. and heated on the water-bath. treated with a cooled mixture of 15 grammes of concentrated sulphuric acid and 20 grammes of water. 66). with the aid of a wide adapter or funnel (Fig. Should the ether begin to ascend in the connecting tube. The name of the class of compounds is derived from this action: Aldehyde = Al(cohol)dehyd (rogenatum).ALIPHATIC SERIES 145 30 0 (the lower side-tube of the condenser is closed with rubber tubing and a pinch-cock). which in many cases serves as a method of preparation. CH 3 . and well cooled with ice and salt. 10 grammes of aldehydeammonia are dissolved in 10 grammes of water. a current of dry ammonia (see page 348) is conducted.CH 2 . But in the preparation of the simplest aldehyde (formaldehyde) from an alcohol a different oxidising agent is . and the aldehyde that is not condensed passes over. an aldehyde is first formed: /-"TT ("""ON. On passing a mixture of the vapour of methyl alcohol and air over a heated copper spiral. or calcium carbonate.CO. soluble in water. It will be referred to under benzaldehyde. the two halogen atoms are replaced by one oxygen atom: CH.Oca = CH3. If sodium amalgam is allowed to act on acid-anhydrides.CHC12 + H2O = CH 3 . potash. one of which has been already mentioned under acetic anhydride.CHO + CaCO3 The lower members of the aldehyde series are colourless liquids. If these are boiled with water. viz.CO. or. formaldehyde is produced. by two methods.CO. The boiling-points of the aldehydes are lower than those of the corresponding alcohols. viz. but insoluble in water... aldehydes can be prepared from their oxidation products. better. The second method. etc.CO/ But this reaction is of little practical value for the preparation of aldehydes.CHC12 + H2O = C 6 H 5 .CHO + 2 HCi Ethylidene chloride C6H5. which is the real preparation method.OH CH3. the carbonic acids. . While by the first reaction one proceeds from substances which in comparison with the aldehydes are oxidation products of a lower order.I46 SPECIAL PART used. water containing sodium carbonate. the higher members are solid. Finally. *' )O + H 2 = CH3.CHO + CH3. lead oxide. the aldehydes may also be obtained by a second method involving the use of compounds of the same substitution series.Oca + H. crystallisable substances. consists in the dry distillation of a mixture of the calcium or barium salt of the acid with calcium or barium formate: CH3. the dihalogen derivatives of the hydrocarbons containing the group CHC12 or CHBr2. the oxygen of the air. The intermediate members are also liquids. possessing pungent odours.CHO + 2 HCI Benzylidene chloride Benzaldehyde This method is used on the large scale for the manufacture of the commercially important benzaldehyde. the deposition is especially beautiful if the vessel has previously been treated with a solution of caustic soda to remove any fatty matter. 21 0 (CH3. CHO + Ag2O = CH3. silver nitrate: CH8.) EXPERIMENT : Fuchsine-sulphurous acid is prepared by dissolving fuchsine in water. a violet-red colour will be produced. The reaction frequently takes place at the ordinary temperature.ALIPHATIC SERIES 147 5CH3.g.CHO -. EXPERIMENT : To as much diazobenzene sulphonic acid as can be held on the point of a knife. To a few cubic centimetres of this solution add several drops of aldehyde.c.OH . of water. Another reaction which can also be employed for the recognition of aldehydes.CHO « " 500 iCH 3 . e. CO. .OH Upon this action depends the fact that aldehydes cause metals to separate from certain salts. 1635 and 1828. .. a sufficient quantity of the latter is taken to prevent the solution from being too intense in colour. but in many cases only on gentle warming. add 5 c. Boiling-point.CO. On shaking. Sulphur dioxide is conducted into this until a complete decolouration takes place.CHO + O = CH3. a few drops 1 B.CH2. they give a violet colour. . depends upon the fact that they give a red colour to fuchsinesulphurous acid. The reaction is used for the detection of aldehydes.CH3. (Caro's reaction. 15. Silver will be deposited in the form of a brilliant mirror on the walls of the vessel.CH 2 . " « « 7S° (CH3. . Finally aldehydes may also be detected by a method depending upon the fact that when treated with diazobenzene sulphonic acid and sodium amalgam. « « 970 Aldehydes are oxidised to acids by free as well as combined oxygen (compare benzaldehyde) : CH3. OH + Ag2x EXPERIMENT : Treat a few cubic centimetres of a diluted silver nitrate solution with a few drops of ammonium hydroxide and 5 drops of aldehyde.OH.CH. CHO + NH3 = CH3. OH It is wholly characteristic of the aldehydes that they unite directly (1) with ammonia. the free aldehyde is obtained. (2) sodium hydrogen sulphite. The union with sodium hydrogen sulphite takes place in accordance with the following equation: /OH CH3.c. formic aldehyde and most of the aromatic aldehydes behave differently toward ammonia.CH< \SO 3 Na Sodium-o-oxyethyl sulphonate This reaction may also be used for the purification of aldehydes.. CH2. of aldehyde and shake the mixture. as in case of acetaldehyde.g. . The union with ammonia takes place in accordance with the following equation: /OH CH3. After some time the red-violet colour appears. Thus.CH< \NH2 Aldehyde-ammonia= a-amidoethyl alcohol This reaction is not so common as the second and third.) EXPERIMENT : Treat 5 c. and then a few drops of aldehyde. and finally a piece of solid sodium amalgam as large as a pea. That aldehydes upon reduction pass over to primary alcohols has been mentioned under acetic anhydride: CH3. by allowing the well-crystallised double compound to separate out.I48 SPECIAL PART of caustic soda. the double compound generally separates out in a crystallised condition. e. (Compare benzaldehyde. The double compound separates out in a crystallised condition. Whenever this reaction does take place it can also be used with advantage for the purification of the aldehyde. The free aldehydes can be obtained from the sulphite compounds by heating with dilute acids or alkali carbonates. CHO + H2 = CH3. on treating it with dilute sulphuric acid. since when a concentrated solution of the sulphite is employed.c. of a cooled concentrated solution of sodium hydrogen sulphite with 1 c.CHO + SO3NaH = CH3. and (3) hydrocyanic acid. CH-CH3 CH 8 . page 279. or if at the ordinary temperature gaseous hydrochloric acid.CH<( a-oxyproprionitrilc This reaction is of especial interest. that the ketones.CH—CH. a solid polymerisation product. Concerning the value of this reaction for the synthesis of a-oxyacids. but that three molecules are united by means of the oxygen atoms: O . If aldehyde is cooled and treated with sulphuric acid. show similar reactions: CH. and is frequently of great value in dealing with the aldehydes of the aromatic series. Acetone ' I 'ov^i CH3 The addition of hydrocyanic acid to ketones as well as to aldehydes is also general: /OH CH3. For this reason it is believed that no new union of carbon atoms takes place in the molecule.. of aldehyde with one drop of concentrated sulphuric acid. since the addition of a new carbon atom is brought about. . this reaction is wholly general. sulphur dioxide. Paraldehyde does not show the characteristic aldehyde reactions. on distillation with dilute sulphuric acid it is converted back into the ordinary variety.CHO + HCN = CH3 . The compound thus obtained is called paraldehyde. and polymerisation (condensation) takes place. EXPERIMENT: Treat 1 cc. It should be noticed in this connection. The aldehyde boils. or other compounds are passed into it. the determination of its vapour density shows that one molecule is composed of three molecules of ordinary aldehyde. it boils much higher (1240) than ordinary aldehyde.CH^ No O . Aldehydes possess further a marked tendency to combine with themselves (polymerise).ALIPHATIC SERIES 149 As distinguished from the union of aldehyde with ammonia. see Mandelic Nitrile. which are closely related to the aldehydes. not exist in the free condition + H2O Piphenyl ethane . Aldol loses water easily. CHO Aldol This compound. CHC12 4. CHO = CH S . N H . C6H5 = CH 3 . finally. NH. CHO + CH 3 . CH 2 .. CH (OH) . C 6 H. EXPERIMENT : Treat a few cubic centimetres of caustic potash solution with several drops of aldehyde. CHzrN. The aldehydes undergo a wholly different kind of polymerisation under certain conditions. CH 3 . to represent the great activity of the aldehydes. is a true aldehyde. In order. For example. this can also be converted back into the ordinary variety. + H 2 O / =CH3. is formed. as distinguished from paraldehyde and metaldehyde. when heated with alkalies. it may be pointed out that many aldehydes. CHO + NH 2 .. CHO + PC15 CH 3 . two molecules of acetaldehyde can unite with the formation of a compound in which a new carbon union is present. CH (OH). A yellow colouration takes place with the separation of a resinous mass. C H . in that it cannot be converted back to acetaldehyde.: C H . CH < g g which doe (. concerning which reference must be made t o the chemical literature and treatises. CHO Crotonaldehydc In connection with these condensations.I5O SPECIAL PART metaldehyde. C H n N O H + H2O Aldoximc Hydrazone of aldehyde CH 3 . the ether of aldehydehydrate CH 8 .POC13 Ethyhdene chloride = CH. the following equations are given : CH 3 . and is converted into an unsaturated aldehyde: CH 3 . CHO = CH 3 . polymerise to resinous products of high molecular weight (aldehyde resins).CH(( f X + HaO OC 2 H 5 Acctal. OH Phenylhydrazinc = CH. CHO + NH 2 . CH 2 . and warm. the finely pulverised substance is crystallised from absolute alcohol. This reaction-mixture is then. 17. The methyl amine is then distilled off with steam.c. the distillation is discontinued. add a solution of 40 grammes of caustic potash in 350 c. of water (the flask is well cooled with water). then to dryness on the water-bath. Yield. In order to separate the methyl amine salt from the ammonium chloride mixed with it. 762. the end of it dips directly into the acid. the end of the condenser is connected with an adapter which dips 1 cm. below the surface of the liquid in the receiver.) of bromine contained in a J-litre flask. of water heated to 70-750. The methyl amine hydrochloride is partially evaporated in a porcelain dish over a free flame.ALIPHATIC SERIES 9. As soon as the liquid in the condenser no longer shows an alkaline reaction. In order that the methyl amine may be completely absorbed by the acid. If a coil condenser is employed. which has been previously well pressed out on a porous plate. 1 B. and is finally heated for a short time in an air-bath at ioo° to dusty dryness. . the flask must be cooled by immersion for a short time in cold water. allowed to flow from a dropping funnel in a continuous stream into a litre flask containing a solution of 80 grammes of caustic potash in 150 c. until the brownish red colour formed at first is changed to a bright yellow. varying. and collected in a receiver containing a mixture of 60 grammes of concentrated hydrochloric acid and 40 grammes of water.c. in the course of a few minutes. In case the temperature rises higher than 750. REACTION: PREPARATION OF A PRIMARY AMINE FROM AN ACID-AMIDE OF THE NEXT HIGHER SERIES EXAMPLE: Methyl Amine from Acetamide1 To a mixture of 25 grammes of acetamide. for which the greater portion of the potash solution will be required. and 70 grammes (23 c. The liquid is maintained at this temperature until it becomes colourless. 15.1406 and 1920. which usually requires a quarter to half hour.c. B. and the crystals separating out dried in a desiccator. CH 2 . With the higher members of the series. is not of general importance. since these 1. in its last phase. and an ester of isocyanic acid is formed: CH 3 . .152 SPECIAL PART Under the discussion of acid-amides. it has already been mentioned that the hydrogen of the amido group (NH 2 ) can be substituted by bromine. NH 2 -I. CONHBr = CH V N ~ C O + HBr Methyl isocyanatc If the attempt is made to eliminate hydrobromic acid in the presence of water by the use of caustic potash solution. but the isocyanate is unstable in the presence of alkalies. is.NH 2 + Br4 + 4 N a 0 H = C 7 H W . a monobromamide is formed. to the discovery of the primary amines. the position of the carbonyl group (CO) is changed. If a 10 % solution of caustic potash is added to a mixture of one molecule of the amide and one molecule of bromine. the primary amine of the next lower series may be obtained from any acid-amide. If hydrobromic acid is abstracted.. W.g.NCO + H2O = CO2 + C H V N H 3 Methyl amine This reaction. since the bromine acts upon the primary aminc to form a nitrile: C 7 H 15 . until the brownish red colour of the latter has vanished. since the elimination of carbon dioxide takes place. NHBr + KBr + H 2 O The monobromamide may be isolated in pure condition in the form of colourless. the reaction in part proceeds still further.Br2 + KOH = CH. which contain the amido group in the benzene ring.. acetmonobromamide in accordance with this equation: CH 3 . In the aromatic series. and secondly. By use of it. e.CEN 4Octyl amine Octonitrile There is thus obtained from the higher members (compounds having five or more carbon atoms) of the amides. The Hofmann reaction is capable of general application. identical with the historical reaction of Wurtz. the reaction for the preparation of primary amines. therefore. in 1848. no water being present. hydrous crystals. discovered by A. the above reaction takes place. and decomposes immediately by taking up the water forming carbon dioxide and a primary amine: CH 3 . CO . first the primary amine. the nitrile of the next lower acid. in the above case. Hofmann. which led him. CO. NH 2 + HI In tMs case. if the above reaction is employed.OH O \C O. NH 2 + O = C6H5.or can be prepared only with difficulty. Primary aliphatic amines can also be prepared according to the following equations: (1) By the action of alcoholic ammonia on halogen alkyls: CH3I + NH 3 = CH 3 . CO . the Hofmann reaction in this case gives a very convenient method of preparation for the ami do-acid. and since.NHBr C6H4< +Br 2 =C 6 H 4 < +HBr \CO.OH which in accordance with the following reactions gives the amido-acid.OH 4< /C O. there is first formed. bromine substitution products are easily formed. CH 2 .OH \CO. the reaction is also of importance in the aromatic series. on the other hand.OH Since the nitro-acid corresponding to the o-amido benzoic acid is difficult to obtain. If. used in the manufacture of artificial indigo.NHBr = C6H4< \CO.ALIPHATIC SERIES 153 y^ be obtained from the easily accessible nitro-compounds.NH2 NH + H2O = C 6 H / \CO.NH 2 /CO. CH 2 . If phenyl acetamide is treated in accordance with Hofmann's reaction. Two cases of this kind may be mentioned in this place. are also formed. But in those cases in which the nitro-compound corresponding to the amine is not known. NH 2 + CO2 Phenyl acetamide Benzyl ajtnine Further. /C0. by the addition of water. as above. and phthalimide is easily prepared. secondary and tertiary bases. bromine and caustic potash are allowed to act on phthalimide. /CO. or the corresponding ammonium compounds. .OH /NH 2 /NzzC—O + HBr + CO2 /N=C=O C8H4< + H2O = C 6 H / \CO. an acid-amide. the reaction is of practical value in the preparation of o-amidobenzoic acid.OH \CO.. there is formed in the usual way benzyl amine: CCH5. T c:H i V CH 3 -Nn a •»• HoO Acctakloximc C H v C H r N . under the aromatic amines. and warm gently.Hrt + 2 H a ~ C H V C I L . l Cf. or caustic soda. At this place. possessing odours suggestive of ammonia: they differ from ammonia in being inflammable. EXPERIMENT : Treat some solid methyl amine hyclroc.OH -h NH:I ~ C a II 5 .NH a (4) By the reduction of nitro-compounds : CH V NO. NH.C<. Since they are derivatives of ammonia.hioride in a small test-tube with a concentrated solution of caustic potash.. r CII a . AuCl. smelling like ammonia.NH a . is evolved. one difference between the aromatic and aliphatic amines will be pointed out.154 SPECIAL PART (2) From alcohols and zinc chloride-ammonia: C 2 H 5 . unite with acids to form salts.NH (NH 4 Cl) a PtCl 4 —*.. If nitrous acid is allowed to . HCl) a PtCl 4 NH4C1.—•. A gas.CH 8 . + 3 Ho -r CM. and.HCl. AuOL.NH a -f l-Lfi (3) By the reduction of nitriles (Mendius1 reaction) : CH V CN + 2 I L r= CH. which burns with a pale flame. Use was made of this property above. like ammonia. The hydrochlorides of organic bases are distinguished from ammonium chloride by their solubility in absolute alcohol. since. NH a Ethylidenc phcnyl hydrazonc Aniline The lowest members of the amines in the free condition are gaseous compounds soluble in water. The numerous reactions of the primary amines need not be mentioned here.. the composition of which is analogous to that of the ammonium compounds: N H r HC1—^CH8.NH.(CH V NH a . The higher members are liquids or insoluble solids. they possess basic properties. NIL -f 2 HaO (5) By the reduction of oximes and hydrazones: CH V CH N.OH •{• 2 l i 2 -.HA. frequent reference will be made to them. for some hours.. an aromatic amine is converted into a diazo-compound (see Diazo-compounds).ALIPHATIC SERIES 155 act on an aliphatic primary amine. All parts of the apparatus must be perfectly dried. in a well-closed flask. over night at least. and the end of iA. dried over calcium chloride. 186. as described on page 137. it contains too much alcohol. if. it will be attacked very slowly by sodium. the following method of procedure gives a good yield and is one that does not fail. The yield of acetacetic ester may be further increased if the acetic ester. under these conditions. and is then filtered. etc. If commercial acetic ester is to be used. it may be used for the successful preparation of acetacetic ester. over about \ its volume of granulated calcium chloride. after the distillation. even after it has been freed from acetic acid and alcohol by shaking with sodium carbonate and calcium chloride respectively. it must be shaken with a sodium carbonate solution. after being filtered from the calcium chloride. it is also necessary to allow it to stand over night in contact with calcium chloride. even on heating. care being taken to prevent the absorption of moisture. Purification of Acetic Ester: The acetic ester prepared according to Reaction 6. . on the other hand. if it is completely free from alcohol. an alcohol is formed with evolution of nitrogen: ^ ^^ + N 0 Q H = ^ 0 H + ^ + ^ Q while. and finally rectified. but the yield of the product is varying and usually small. is again distilled.214. Obviously. is not suitable for this preparation. it is treated as the crude product obtained in the preparation of acetic ester. since. the character of the acetic ester used is of great importance. According to the experiments of the author. 10. after distilling. REACTION: SYNTHESES OP KETONE ACID-ESTERS AND P0LYKET0NES WITH SODIUM AND SODIUM ALC0H0LATE EXAMPLE: Acetacetic Ester from Acetic Ester and Sodium1 For the successful preparation of acetacetic ester. since it reacts too violently with sodium. treated with calcium chloride solution. But if it is allowed to stand. the sodium acts easily. in short. it is dissolved by adding some water. gentle boiling. To the warm liquid is added a mixture of 80 grammes of glacial acetic acid and 80 grammes of water. until it just shows an acid reaction. To separate the acetacetic ester from the main portion of the excess of the acetic ester used. heated by a free flame over a wire gauze. no violent ebullition will occur. but is held in the hand. without the wire gauze. by allowing it to run off from a dropping funnel. the mixture is distilled from a flask.156 SPECIAL PART the condenser tube must be connected to the receiver (suctionflask) by a good cork. After small quantities of acetic ester. The heating is done in an air-bath. the heating is discontinued. 250 grammes of dried acetic ester is poured into the top of the condenser. the reactionmixture is heated until all the sodium is dissolved. 89) into pieces as thin as possible. so that the air may escape. Should a precipitate settle out on the addition of the salt solution. consisting of acetic ester and acetacetic ester. as described on page 25. and the residue is subjected to vacuumdistillation. more conveniently. the flask is placed on a previously heated water-bath. water. In place of the usual condenser. porridge-like mass should separate out. and water is allowed to circulate through it. this is again dissolved by vigorous shaking. As soon as the thermometer indicates 950. inclined at an oblique angle. Preparation of Acetacetic Ester: 25 grammes of sodium from which the outside layers have been removed are cut with the aid of a sodium knife (Fig. After 10 minutes. If the acetic ester is added properly. the temperature of which is so regulated that the acetic ester boils but gently. but at first a gradual. by a funnel which must not be attached to the condenser. and placed in a dry litre-flask. or. which will require from 3-4 hours. If a thick. To the liquid is then added an equal volume of a cold saturated solution of sodium chloride. and the lower aqueous layer is separated from the upper one. with a luminous flame. After this is connected with a long reflux condenser. and acetic acid have . the outside jacket of a Liebig condenser is pushed over the long side-tube of the distillation flask. or carefully breaking up the small lumps with a glass rod. COOC2H5 -f C2H5. the sodium first acts on the alcohol. CO |OC 2 H 5 4-H. CO. OC2H5 + C2H5 -ONa = CH3. must be present in small quantities. takes place in accordance with the following equation: CH 3 . C(-OG>H5 \ONa Reaction then takes place between this addition product and a second molecule of acetic ester. and this unites with the acetic ester as follows: /OC 2 H 5 CH3. In the preparation of this substance. According to the views of Claisen. The following table gives the boiling-points at various pressures. the acetic ester heated with sodium at midday. which. discovered by Geuther in 1863. as above mentioned. The operation should be begun in the morning. CO. CH2. the yield is essentially diminished. CO. the temperature becomes constant. If the reaction is discontinued at any point.5 mm.ALIPHATIC SERIES 157 passed over. and the formation of the sodium salt of the acetacetic ester: . it must be borne in mind that the experiment must be completed in one day. pressure. OC2H5 = CH3. The formation of acetacetic ester from acetic ester. it it tt tt tt 74° 79° 88° 94° 97° ioow It tt tt tt it 14 18 29 u it tt tt tt 45 59 The yield of acetacetic ester amounts to 55-60 grammes. and the main portion of the acetacetic ester distils over within one degree. A reference to this will show at what approximate points the collection of the preparation should begin: Boiling-point 71 0 at 12. with the elimination of two molecules of alcohol. forming sodium alcoholate. and the experiment completed in the afternoon.| CH2. and the unfinished preparation allowed to stand over night. OH Acetacetic ester But the mechanism of the reaction is much more complicated than here indicated. for this reason it will be briefly mentioned here.OC 2 H 5 (enolform). a ketone dicarbonic acid ester will be formed.CO. is of general applicability.C=CH.CH 2 .CH 2 XO. but polyketones. esters of aldehyde-acids will «6e obtained.OC 2 H 5 Acetic ester =1 CO. OC2H5 + 2 C2H3. e.CO. 205.CO.g.CH 3 + C2H5. CO. it is true. but a reaction closely related to it. is formed by the action of the sodium alcoholate on one of the esters with the elimination of alcohol.CH 2 XO. CO [OC2H5 + H| CH2.OH In place of the acid-ester in the above reaction. / ONa = CH3 .C~CH .CO. Acctylacctone . a ketone may be used. and 601. which is susceptible of many combinations. If sodium alcoholate is allowed to act on a mixture of the esters of two monobasic acids.OC 2 H 5 . the reaction is not capable of general application.1 CH 3 . having a constitution analogous to that of acetacetic ester. e. CH5 Acetic ester Acetone = CH S -CO.: Formic ester Acetic ester Formyl acetic ester If one molecule of a dibasic ester is used.g. the sodium salt is decomposed with the formation of the free ester. OH which spontaneously changes into the desmotropic form (ketoform).CO.OC 2 H 5 * ' +C 2 H 5 .158 OC2H5 SPECIAL PART H \cH. CO |OC2H5 -f H| CH 2 .OH If one of the compounds is formic ester.: C 6 H 5 .OC 2 H 5 Oxalic ester CO.CH 2 .g. and is of great value in synthetical operations.CO. discovered by Claisen and W. 31. CO. In the form indicated above. COOC2H5 Benzoic ester Acetic ester • Benzoyl acetic ester = C 6 H 5 . e. or ketone-aldehydes: CH 3 .OC2H5 OC2H5 + H . a ketone acid-ester.: CO. a ketone acid-ester is not formed.OH _ l B.OC 2 H 5 + C 2 H 5 . OH ONa On acidifying with acetic acid.OC 2 H/ Oxalacetic ester CO. CH 3 . Wislicenus.OG>H3 I + HLCH 2 .CO. CHNa. C H H . CO . CH 2 . CHNa.CO. OH Benzoylaldehyde These few examples are sufficient to show the many-sided applications of t h e above reaction. A few typical examples may elucidate these statements: (1) C H 3 . with the condensation of the two remaining residues. CO. If sodium is allowed to act on it.CO. OC2H5 + Na = CH 3 . CO. The synthetical importance of acetacetic ester depends on the fact that the most various organic halogen substitution products react with sodium acetacetic ester.|CH 2 . CH 2 . The most remarkable characteristic of acetacetic ester is that a portion of its hydrogen may be substituted by metals. CHNa. CO. the acidifying influence of the two neighbouring carbonyl (CO) groups. Thus a large number of compounds may be built up from their constituents. Cl Benzoyl chloride = CH 8 . CO. COOC2H6 + a . OC2H5 = Chloracetic ester CH 3 .OC 2 H 5 CH2 COOC 2 H 5 )C Acetsuccinic ester + NaCL . the sodium salt is formed with the elimination of hydrogen: CH 3 . CHNa.CO. CO. CO. OC2H5 + Nal Methylacetacetic ester (2) C H 3 • CO.CO. COOC2H5 + ICH3 = CHS. CO . CO. j g T ^ Acetophenone Formic ester = OzuCH. OC2H5 + N a d CO Benzoylacetacetic ester l C6H5 _ X5 (3) C H * .CO. C 6 H 5 + C 2 H 5 . the halogen uniting with the sodium.CH. OC2H5 + H The s a m e salt is also formed by shaking the ester with a solution of sodium hydroxide. CO. CO. The reason for this phenomenon is to be sought in. CO.ALIPHATIC SERIES C 6 H 5 XQ[QC 2 H 5 + H. CO. CH 2 . OC2H5 + C6H5. CH.CH 3 + Bcnzoylacetoae 159 H.. CO.CH .CH 3 Benzoicester = C6H5. C O . OC 2 H 5 + IC2H5 = CH 3 XO. may be united with one another by the most various bivalent radicals. aldehyde-ammonia.OH. X.OC 2 H 5 +NaL Sodiumraethylacetacetic ester Methylethylacetacetic ester From all these compounds simpler ones may be obtained on saponification. This action will be referred to later in the appropriate places.CH 3 as well as mono. etc. depending upon the conditions of the saponification: CH3.substituted acetones: X\ X. e.160 SPECIAL PART In the compounds thus obtained the second methylene hydrogen atom is also replaceable by sodium.CH2.OH. phenyl hydrazine. Acetone CH3. e.C—CO.CH 3 and ">CH. and this salt is likewise capable of entering into similar reactions. these substances yield either mono. by reaction with aldehydes or alkylene bromides. = 2CH 3 .C." the second. by which the number of derivatives is largely increased. it also reacts with nitrogen compounds.CO.CO.g. "acid decomposition.CO..CO. These examples are sufficient to show the value of acetacetic ester and analogous compounds for organic syntheses. The acetacetic ester breaks up in one of two ways.OH+C 2 H.OH and VH.CO.or di.g.. but.substituted acetic acids.CH 2 .CO." Since.: CH s .and di.CO. aniline. X or Y. Acetacetic ester may not only be employed for the syntheses of carbon compounds. Acetic acid The first kind of decomposition is called " ketone decomposition.CO. either one or both of the methylene hydrogen atoms in acetacetic ester can be replaced by different radicals.CH 2 . as shown above. The variety of the acetacetic ester syntheses is still further increased by the fact that two molecules of the ester. .Na~-CO. When the reaction is complete. with vigorous ebullition. warm gently (about 500). the mixture is evaporated as quickly as possible on the sand-bath until a thermometer placed in the viscous .c. while 40 grammes of pure. and treated with 20 c. two hours in a water-bath (hood) . It is allowed to cool. The pasty mass is now heated. It is then quickly powdered as finely as possible. the hand being protected by a glove or cloth. with frequent shaking. otherwise the product bakes into a hard.c. and neutralise with solid. The solution is then heated gradually. potassium carbonate. is then carefully extracted with a sufficiently large quantity of ether. placed in a -J-litre flask provided with a reflux condenser. dry. ( Owing to the copious evolution of gas the funnel is not closed at first) It is then dried over fused Glauber's . of concentrated sulphuric acid is then added gradually. of water (shaking). Since the substance "bumps" and spatters during the evaporation. it is constantly stirred with the thermometer. of absolute alcohol and So c. with good shaking. consisting of the water solution and the ether washings. with thorough stirring.brownish salt indicates 1350. scarcely pulverisable mass. finely pulverised potassium cyanide are added. and treated with 150 c. under the hood.) The formation of cyanacetic acid takes place. REACTION: SYNTHESES OF THE HOMOLOGUES OF ACETIC ACID BY MEANS OF MALONIC ESTER EXAMPLE : Butyric Acid from Acetic Acid (a) Preparation of Malonic Ester Dissolve 50 grammes of chloracetic acid in 100 grammes of water. (Use a sand-bath or asbestos plate. it is then well cooled.c. for which 30-40 grammes will be required. it is washed on the filter several times with ether. The ethereal extract is shaken up in a separating funnel with a concentrated solution of sodium carbonate until it no longer shows an acid reaction. A cooled mixture of 80 c. the stirring being continued during the cooling. through the condenser tube.c.ALIPHATIC SERIES i6l 1 1 . After the undissolved salt has been filtered off with suction. of absolute alcohol. The filtrate. a concentrated solution of -fustic. (c) Saponification of Ethyl Malonic Ester For the saponification of the ester. probably potassium ethylmalonic ester. add through the condenser 20 grammes of ethyl iodide in small portions. an emulsion is first formed.3 grammes of sodium in 25 grammes of absolute alcohol in a small flask connected with a reflux condenser. the ether evaporated. The compound may also be advantageously dried. by evaporating off the ether. through this the ester is gradually added . (Compare page 49. to boil. a thread being placed in the flask to facilitate the boiling. The heat generated in the reaction causes the alct>hol. the oily layer disappears. Yield. for which one or two hours may be necessary. and the residue distilled.— and then. 1950. After about an hour's heating on the water-bath. On heating the mixture on abater-bath a sudden energetic boiling-up sets in. for every gramme of the ester. liberated in the saponification.) (b) The Introduction of an Ethyl Group Dissolve 2. and heating the residue about a quarter hour in a vacuum on a water-bath. potash is prepared.— the transparent crystals of sodium ethylate separating out at first pass over into a-voluminous pasty mass of sodium malonic ester. a solution of 1. distilled. about 15 ^grammes. about 40 grammes. showing that the saponification is complete. . treat the cooled solution gradually with 16 grammes malonic ester. The cooled solution is placed in a flask provided with a reflux condenser.25 grammes potassium hydroxide in 2 grammes of water^ used. The mixture is then heated on the water-bath until the liquid no longer shows an alkaline reaction.162 SPECIAL PART salt. especially if the flask be shaken. and after the evaporation of the ether. Boiling-point. Yield. with shaking. which soon solidifies to a white solid mass. without the use of Glauber's salt. the residue is taken up with water and extracted with ether. The alcohol is then distilled off on an actively boiling water-bath. Boilingpoint. 206-2080. the potassium cyanide acts on the chloracetic add. which will require about a half-hour. in a large watch crystal or 'dreh^untll it begins to solidify. The ethyl malonic acid is precipitated out in the form of its difficultly soluble calcium salt. Yield. the ether evaporated.5°. The residue is distilled from the same flask in the usual way. After cooling. until carbon dioxide is no longer evolved. The mouth is clos. and the residuwfe|te$f with stirring. The ethylmalonic acid liberated is taken pip \yith not too little ether. as concentrated as possible. with the formation of cyanacetic acid : .ALIPHATIC SERIES 163 The free ethyl malonic acid may be obtained by following either of the methods given below : (1) The solution is diluted with i£ times the volume of water previously used to dissolve the caustic potash. about 7 grammes. 111. To this is added carefully and with cooling concentrated hydrochloric acid. or on its potassium salt. by the addition of a cold solution of calcium chloride. This is filtered off. Yield. (a) In the first phase of the reaction which gives ethyl malonic ester. the butyric acid passes over between 162-163°. The acid is heated at 1800. about 80-90% of the theory. the ethereal solution dried over an$ydi0tsl Glauber's salt. it is pressed out on a drying plate and crystallised from benzene. so that its outlet tube is inclined upward. (2) The solution is diluted with the same volume of water previously used to dissolve the caustic potash. Melting-point. gradually. until an acid reaction may just be detected.ed by a cork bearing a thermometer. (d) Elimination of Carbon Dioxide from Ethyl Malonic Acid The ethyl malonic acid is placed in a small fractionating flask provided with a long condensing tube supported in an oil-bath at an oblique angle. and the ethyl malonic acid liberated by treating carefully with concentrated hydrochloric acid is obtained pure as in (1). well pressed on a porous plate. To this is added. a quantity of concentrated hydrochloric acid equivalent to the total amount of caustic potash used (the strength of the acid is determined by a hydrometer). with cooling. on a water-bath. the sodium salt of the malonic ester is first formed from sodium alcoholate and the ester: . OH + KCN = CH 2 . OH CO..e. the cyanogen group is converted into carboxyl (COOH). halogen derivatives of acid-esters. OH CH 2 . it has already been brought forward that. three reactions take place.OC 2 H 5 Acid ester of malonic acid +NH3 The carboxyl group thus formed is then acted on in the same way as the carboxyl group of cyanacetic acid abovej with the formation of an ester: CO. In the second place. CO.CO.CO. like acetacetic ester.SPECIAL PART CH2C1. in consequence of the acid properties imparted by the two neighbouring carbonyl (CO) groups. At first there is an esterification in accordance with the equation: CH 2 . CO. CO. etc. acid-chlorides.OH + C 2 H 5 . OH = CH 2 CO.CO. If alcohol and sulphuric acid or ethylsulphuric acid are now allowed to act on the cyanacetic acid. just as in the case of the closely related acetacetic ester. the sulphuric acid has a saponifying action on the cyanacetic ester. on heating with potassium or silver cyanide.OC 2 H 5 CH2 CO..C2H5. OH + KC1 Cyanacetic acid As already mentioned in the preparation of acetonitrile.OC2H5 4.( 2 H 5 CO.OC Malonicdiethyl ester + H2O (J>) The ester of malonic acid.OC 2 H 5 + 2 H2O = CH2 CO..CN. possesses the property in virtue of which one of the two methylene hydrogen atoms can be replaced by sodium. In the above-mentioned examples.OH = CH. in general.CN. etc.. like alkyl halides. a halogen united with aliphatic residues may generally be replaced by the cyanogen group. acid esters can be obtained by treating a mixture of the alcohol and acid with sulphuric acid. When the sodium compound is treated with organic halides. the sodium is replaced by alkyl residues. CN. i.CN.OC 2 H 5 + H2O Cyanacetic ester Under the discussion of acetic ester. acid residues. C 2 H 5 + Nal I CO. the ethylmalonicdiethyl ester reacts with caustic potash as follows: CO. By this means.OC2H5 are distinguished from the corresponding derivatives of acetacetic ester in that on saponification they do not decompose. derivatives of acetic acid may be prepared by heating it to a high temperature.OC2H5 CH|Na + l|C 2 H 5 =CH. OK (d) From the substituted malonic acid thus obtained.OC 2 H 5 L -X iH and C I /& I iO. OK = CH.OC 2 H 5 CH.OC2H5 KOH CO. but yield the free substituted malonic acids. C2H5 + 2 C2H5. a dicarbonic acid is converted into a monocarbonic acid.g.ALIPHATIC SERIES CO.OC2H5 Ethylmalonicdiethyl ester As in acetacetic ester. consequently the malonic ester is capable of reacting a second time with organic halides.OC2H5 CO.: • . (c) The compounds thus obtained of the general formulae: CO. C2H5 + KOH CO.OC 2 H 5 " CO. so that disubstituted malonic esters can also be prepared. It is a general law that one carbon atom cannot hold two carboxyl groups in combination at high temperatures.OC 2 H 5 I CO.OC2H5 CO. the second hydrogen of the malonic ester can also be replaced by sodium.6] Na = CHNa CO. e.OQH 5 Ethyl iodide reacts on this as follows: CO.OC2H5 + C2H5.OC 2 H 5 CO. OH CO. OH 165 CH |H + C ? H 5 .OC 2 H 5 CO. since carbon dioxide will be eliminated from one. Thus. COMBINATION OF THE HYDROCARBON WITH BROMINE | o | r CH< V EXAMPLE : Ethylene from Ethyl Alcohol. and it is advisable to empty the flask and begin the operation anew. A. so in most cases it is more advantageous to use the malonic ester for the synthesis of the homologous fatty acids. and a second one. 1 2 .144. Since the decomposition of the acetacetic ester derivatives may take place in two different ways (acid. on decomposition. in a litre round flask on a wire gauze covered with thin asbestos paper. so that a regular stream of gas is evolved. provided with three tubulures.or di. a mixture of 1 part alcohol and 2 parts concentrated sulphuric acid (made by pouring 300 grammes of alcohol into 600 grammes of sulphuric acid. OH Thus from ethylmalonic acid. 64. then. and sulphur dioxide. instead of ethyl iodide. 192.OH CO. If two methyl groups are introduced into malonic ester. . a dimethylacetic or isobutyric acid will be formed. 168. not too strongly. it is passed through a wash-bottle containing sulphuric acid. add.and ketone-decomposition) . 67). As shown above. and since these decompositions frequently take place side by side. proprionic acid or valerianic acid respectively is obtained. it has been too strongly heated. Ethylene Bromide1 A mixture of 25 grammes of alcohol and 150 grammes of concentrated sulphuric acid is heated.166 SPECIAL PART From the mono. there is formed ethylacetic acid = butyric acid. If. with constant stirring). CO. similar acids may be prepared from the acetacetic ester. slowly. the central one sup1A. through a dropping funnel. If the mixture in the flask foams badly with a separation of carbon. ether. In order to free the ethylene from alcohol. As soon as an active evolution of ethylene takes place.substituted malonic acid a substituted acetic acid is obtained of the formula. methyl or propyl iodide is used. or sand bath (Fig. REACTION: PREPARATION OF A HYDROCARBON OP THE ETHYLENE SERIES BY THE ELIMINATION OP WATER FROM AN ALCOHOL. while the malonic acid derivatives decompose in only one way. and. to prevent the caustic soda from being drawn back into the bromine bottle. 125-150 grammes. is obtained perfectly pure.not dip under the surface of the caustic soda. 1300. and. It is dried over calcium chloride. It then enters two wash-bottles. finally. of bromine. in consequence of the cooling of the large flask. In order to get rid of the bromine vapours which escape from the last bottle. it is connected with the hood or with a flask containing a solution of caustic soda. the bromine bottles are placed in thick-walled vessels filled with cold water. containing a dilute solution of caustic soda. 67. Boilingpoint. the delivery tube must . covered with a layer of water 1 cm. The addition of the alcohol-sulphuric acid mixture is often attended with difficulty. otherwise. thus preventing the entrance of the mixture. The ethylene bromide is then washed repeatedly with'water in a dropping funnel. This difficulty may be obviated by taking the precaution of always keeping the stem of the funnel filled with the mixture. each containing 25 c. high. . in that as soon as the cock is opened. the contents of the bottles will be drawn back. on distillation. the operation is discontinued. Since the combination of ethylene with bromine causes the evolution of heat. with caustic soda solution. Yield. As soon as the bromine is decolourised. care mbeing taken to disconnect all of the vessels immediately. FIG.ALIPHATIC SERIES 167 plied with a safety-tube. the gas passes out through the funnel.c. CO. C4H8. yields sulphuric acid again: vOH /OC 2 H 5 C2H5. but ethylsulphuric acid is first formed.l6g SPECIAL PART Before the heating is begun. the funnel placed in the cork of the generating flask. on heating.OC16H33 = C 15 H 31 . §moky flames.CH 2 .: C15H31. a portion of the mixture is placed in a porcelain dish. OH + £o 2 = SO2 + H2O \DH \DH Ethylsulphuric acid X)C 2 H 5 /OH SO2 = C2H4 + SO2 X)H X)H In many cases the elimination of water takes place so easily t h a t the use of concentrated sulphuric acid is unnecessary. since the diluted acid answers the purpose. by abstracting water from the corresponding alcohol.g.OH + C16H32 Cetyl palmitate Palmitic acid Hexadccylenc The first four members of the alkylene series are gases at ordinary temperatures. the reaction does not follow the above equation.g. besides butylene. hydrocarbons having respectively twice and three times its molecular weight. e. Thus there is formed.: CH 3 . which burn with strongly luminous. the end of the stem of the funnel immersed in it and filled by suction.CO. e. If sulphuric acid is used as the dehydrating agent.: C8H16 Dibutylene c H i2 24 Tributylene In these cases it is much more convenient to prepare an ester from the alcohol by the action of the chloride of a higher fatty acid. With the higher members of the series t h e reaction is complicated by the fact that the simple alkylenes polymerise under the influence of sulphuric acid. The hydrocarbons of the ethylene series may be prepared. The cock is then closed.OH = CH2=CH 2 + H 2 O. T h e . in general. a n d subjecting this to distillation by which it is decomposed into an hydrocarbon of the ethylene series and the free fatty acid. and the heating b e g u n . and this.g. e. Ethyl iodide The homologues of ethylene also form addition products.OH. not miscible with water. hydrobromic acid with less. or a univalent atom and a univalent radical.CH 2 . two atoms of hydrogen. CHI. the ester is decomposed into alcohol and sulphuric acid: /OC 2 H 5 X)H SO2 + H O H = C2H5. which can be distilled at ordinary pressures without decomposition. thus passing over to the hydrocarbons of the saturated series (paraffins): CH2zzCH2 + H2 = CH3 . especially in the presence of platinum-black. Hydrogen. CH 3 .OH = CH 3 . X)H X)H so that finally H and OH have been added to ethylene: + H.OH + £o 2 . halides may also be added to them. the halogen atom seeks that carbon atom which is combined with the smallest number of hydrogen atoms: CH 2 izCH. Chemically these compounds are characterised primarily by the property of uniting with two univalent atoms. upon which the double union is changed to single union. the higher members are solids.ALIPHATIC SERIES 169 intermediate members are colourless liquids. They take up. CH3 + HI = CHS. If this is boiled with water. Propylene Isopropyl iodide The constituents of water (H and OH) may also be added indirectly to the alkylenes. hydriodic acid with the greatest ease.CH 2 I. If concentrated sulphuric acid be allowed to act on one of them.CH 3 . it dissolves. . forming a sulphuric acid ester: X)H CH2ZzCH2 + SO2 \)H X)C2H5 = SO2 \)H . and hydrochloric acid only with difficulty: CH£=CH2 + HI = CH S . and can only be distilled without decomposition in a vacuum. . CO.CHBr. CHzrCH.170 SPECIAL PART Analogous to the halogen atoms. CH 2 .OH Phenylchlorlactic aci4 CHjizCH.OH. Finally they combine directly with hypochlorous acid to form glycolchlorhydrines. OH + H2O Acrylic acid C6H5.CH2C1 CH2z=CH2 + Br2 = CH2Br .CH2Br. Thus. The alkylenes take up two atoms of chlorine or bromine with gr^at ease: CH^iCH2 + Cl2 = CH2C1 . CO.OH=C6H5. CO. OH.CO. The reactions taking place in the formation of the alkylenes as well as those in the formation of addition products are not only applicable to the hydrocarbons but also to their substitution products. CH. CHBr .CO.CH2Br.OH4-C1. CH 2 . CH 2 .CH 2 .CH. OH. CHzzCH.CHC1. OH. e. Styrenc dibromide C6H5.g. CO.CO. OH + H 2 O Cinnamic acid All compounds in which the ethylene condition is present show t h e addition phenomena. the hydroxyl (OH) group unites with that carbon atom holding in combination the smallest number of hydrogen atoms. CO. CHBr . OH Dibromhydrine CH 2 =CH.CHBr. Proprionic add .CHBr. in accordance with the following equations : CHsZiCH. CH=CH 2 + Br2 Styrcne = C 6 H 5 . OH Bromhydrocinnamic acid = C6H5. CHzzCH. CHBr . CO. CO. OH Dibromproprionic acid C6H5. CO. OH Dibromhydrocinnamic acid CgH5. CH 2 . OH + HBr C6HS. OH + Br2 Allyl alcohol = CH2Br . CO. CH 2 .CH=CH. CO. OH /3-hydroxyproprionic acid = CH 2 zzCH. OH + H 2 Acrylic acid = CH3. CO. unsaturated acids are commonly obtained from oxyacids by t h e elimination of water: CH 2 . OH + Br2 Acrylic acid = CH2Br . OH + Br2 Cinnamic acid = C6H5. OH Phenyllactic acid = C6H5. ALIPHATIC SERIES 171 13. REACTION: REPLACEMENT OP HALOGEN ATOMS BY ALCOHOLIC HYDROXYL GROUPS EXAMPLE: Ethylene Alcohol (Glycol) from Ethylene Bromide (a) Conversion of Ethylene Bromide into Glycoldiacetate A mixture of 60 grammes ethylene bromide, 20 grammes glacial acetic acid, and 60 grammes of freshly fused, finely pulverised potassium acetate,1 placed in a ^-litre, short-necked, round flask, provided with a reflux condenser, is heated to active boiling for two hours on a sand-bath over a large flame. The reaction product is then distilled (with a condenser) over a large luminous flame kept in continuous motion. Toward the end of the distillation the flame is gradually made non-luminous. The distillate is then further treated with 60 grammes ethylene bromide and 80 grammes potassium acetate, and the mixture, as above, heated to active boiling for two to three hours on a sand-bath. The reaction product is then again distilled over (with a condenser) by a luminous flame. The distillate is fractioned — using a 10 cm. long Hempel tube. The fractions are collected as follows : 1. up to 140 0 ; 2. from 140-175 0 ; 3. above 1750. Fractions 2 and 3 are then again distilled separately. The pure glycoldiacetate goes over between 180-190°, the main portion at 186°. Yield, about 70 grammes. If it is desired to increase the yield, the portion going over under 1800 is heated for three hours longer with potassium acetate. The product is then treated as above described. This causes an increase of about 15 grammes. (F) Saponification of Glycoldiacetate A mixture of 50 grammes of glycoldiacetate and 35 grammes 1 Potassium acetate (Kalium aceticum pur. Ph. G. III.), differing from sodium acetate (compare page 127), crystallises without water of crystallisation. Nevertheless, for this experiment it must be heated to fusion over a free flame in an iron or nickel dish. The melted salt is poured into a shallow, flat iron or copper dish, in a thin layer. While still warm it is pulverised as finely as possible, and must be at once transferred to a bottle which is to be kept tightly closed. For this expert ment 200 grammes of the salt are fused. 172 SPECIAL PART of freshly slaked lime (dried at 1500 in an air-bath), placed in a 150 c.c. round flask, the walls of which are not too thin, provided with a short reflux condenser, is heated in an air-bath — tall iron crucible — for about four hours, at 170-1800; the crucible is covered with an asbestos plate provided with a slit of the proper size. The glycol formed is obtained by a vacuum distillation. For this purpose the flask is connected with a tube — \ in. in length, not too wide, and bent downwards; it is inserted into a short condenser. A 50 c.c. fractionation flask, with the side tube near the bulb, is employed as the receiver. After exhausting the apparatus as completely as possible, the flask is heated in the air-bath (used in the saponification, closed with the asbestos plate) at first to 150°, toward the end to 2000, until no more glycol passes over. Since this is firmly retained by the calcium acetate, which finally becomes as hard as stone, the distillation, at times, must be continued from one to two hours, if a good yield of glycol is desired. In order to separate it from small quantities of the unsaponified ester, which cannot be done through distillation, owing to the slight difference in their boilingpoints, the viscous distillate in the fractionating flask is shaken up twice with an equal volume of dry ether; the glycoldiacetate is taken up, while the glycol remains undissolved. The main portion of the ether is removed with a pipette, and the last portions by carefully heating the upper of the two layers of liquid. The glycol is then distilled over, the fraction distilling above 1850 being collected separately. Yield, 16-18 grammes. Boilingpoint of the pure glycol, 1950. The boiling-point of the compound is somewhat lowered by a small quantity of water. This preparation shows a method for replacing a halogen atom by an alcoholic hydroxyl group. In Reaction 1 the reverse replacement was brought about,—the substitution of a hydroxyl group by a halogen. This method is obviously only of importance in those cases in which it is more convenient to obtain the halogen derivative than the alcohol. Among the monacid alcohols it is of value for preparing isopropyl alcohol, normal secondary butyl, and normal secondary hexyl alcohols,. ALIPHATIC SERIES 173 As stated on page 115, the action of hydriodic acid on polyacid alcohols does not yield, as might be expected, the poly-iodine derivatives, but mono-iodine derivatives. Thus from glycerol, isopropyl iodide is obtained; from erythrite, normal secondary butyl iodide; from mannite, the normal secondary hexyl iodide. These iodides, as pointed out, may be converted into the corresponding alcohols. The method is of practical value in the preparation of tertiary alcohols from acidchlorides and zinc alkyls. — Butlerow's synthesis. Compare page 126. In this reaction the tertiary chloride is formed as an intermediate product. The method is of importance for the preparation of di-acid alcohols (glycols), especially for the a-glycols, in which the hydroxyl groups are Combined with the two adjacent 'carbon atoms. The dibromides corresponding to these alcohols are easily obtained by the addition of bromine to the hydrocarbons of the ethylene series. In this way glycol was first prepared by Wurtz.1 Other glycols may be obtained in a similar manner, e.g., if allyl bromide be treated with hydrobromic acid, trimethylene bromide is formed, from which a /?-glycol—trimethylene glycol — may be obtained by the above reaction. If, to unsaturated mono-acid alcohols containing a double union, two bromine atoms be added, dibrom-alcohols are obtained which, by replacing the bromine with hydroxyl, yield tri-acid alcohols: CH^CH.CHgBr + BrH = CH2Br.CH2.CH2Br - > - CH 2 (OH) .CH 2 .CH 2 (OH) AJlyl bromide Trimethylene bromide Trimethylene glycol CH 3 CH CH 3 CHBr CH3 CH(OH) \\ +Br2= I _>. I CH CHBr CH(OH) CH 2 (OH) CH 2 (OH) CH 2 (OH) From these examples the value of this method for obtaining alcohols is evident. Oxyaldehydes, oxyketones, and oxyacids may also be obtained by this reaction, from the corresponding halogen compounds. Finally, it may be employed to replace the halogen, in side-chains of aromatic compounds, by hydroxyl. The substitution of halogen atoms by hydroxyl groups may be done 1 A. ch. (3), 55, 400. 174 SPECIAL PART by two methods: (i) Directly in a single operation. (2) In two reactions; (a) by preparing an acid-ester of the desired alcohol, and (b) subjecting this to saponification. If method (1) be used, the halogen derivative is heated with water at the ordinary pressure, or if necessary, at an increased pressure. The same object is attained more quickly, and in many cases with a better yield, by the addition to the reactionmixture of certain oxides, hydroxides, or carbonates. Silver oxide, lead hydroxide, barium hydroxide, potassium or sodium carbonate, and others may be used for this purpose. It appears to be true that a tertiary . halogen atom reacts more easily than a secondary or primary, and that a secondary, more easily than a primary. By following this method, glycol may be obtained directly from ethylene bromide, if the latter be heated with water and potassium carbonate: CHJBr CH./OH) I + K0CO3 + H.>0 =' I " + CO2 + 2'KBr CH2Br ' " CH 2 (OH) The separation of the glycol from the large excess of water used is troublesome. In accordance with method (2).certain salts, as silver, potassium, or sodium acetate are allowed to act on the halogen substitution product. This results in the formation of an ester of the desired alcohol: CH2Br CH,,.OOC.CH<> I +2CH3.COOK=| " '+2KBr CH2Br CH 2 .OOC.CH 3 Glycoldiacetate The ester is then saponified under the proper conditions, upon which the free alcohol is obtained: CH 0 . OOC. CH 3 CH 2 (OH) I " + Ca(OH) o = I + (CH 3 .COO) 2 Ca CH 2 .OOC.CH S " CH 2 (OH) Glycol is a thick, colourless, odourless liquid, boiling at 1950; it melts at 11.50 after having been solidified by low temperature. Like all polyacid alcohols, it has a sweet taste. It is easily soluble in water and in alcohol, but not in ether. Chemically it differs only from the mono-acid alcohols in its ability to form mono- or di- derivatives according to the conditions: CH 2 .ONa CH 2 .ONa CH 2 .OOC.CH 3 CH 2 .OOC.CH S I and I ; I and I CH 2 .OH CH 2 .ONa CH 2 .OH CH 2 .OOC.CH a ALIPHATIC SERIES 175 Both hydroxyl groups are replaced by the action of phosphorus pentachloride: CH2(OH) CH2.C1 I " ' + 2 PP C 51 |I +2POCI3 + 2HCI 1 + C1 = :H 2 (OH) CH,COH) CHo.Cl But if glycol be heated with hydrochloric acid, only one hydroxyl group is replaced: CH,>(OH) CH2.C1 I + HC1 = I -f H2O CH2(OH) CH2(OH) Ethylene chlorhydrine From these so-called halogen hydrines, by the action of alkalies the inner anhydrides of the glycols are obtained: CH2.C1 CH«,V I = I ">O + HC1 CH 2 .(OH) CH/ Ethylene oxide 1/6 SPECIAL PART TRANSITION FROM T H E ALIPHATIC TO T H E AROMATIC SERIES Dunethylcyclohexenone and s-Xylenol from Ethylidenebisacetacetic Ester. (Ring Closing in a 1.5 Diketone. Knoevenagel Reaction.1) 1. ETHYLIDEBrEBISACETACETIC ESTER In a thick-walled flask closed by a cork bearing a thermometer reaching almost to the bottom, treat 50 grammes of pure (in vacuum distilled), cooled acetacetic ester with 8.5 grammes of pure aldehyde distilled just before the experiment. The flask is cooled to — 10-15° in a freezing mixture of ice and salt. To the reaction-mixture is then added a few drops of diethyl amine from a small medicine " dropper." In most cases no elevation of temperature takes place at first Since it is very difficult to obtain acetacetic ester and aldehyde absolutely free from acids, the first portions of the amine are neutralised by the acids present, and are thus not available for the main reaction. The addition of the amine is continued slowly until at a certain point an elevation of a few degrees in the temperature is observed. Normally this should occur' on the addition of the first ten drops. When this takes place, the liquid, clear at first, becomes turbid. From this point, during the gradual addition of a further portion of ten drops of the base, the temperature is slowly allowed to rise to o°. The addition of the base in drops is continued, gradually and with frequent shaking, until, collectively, 60 drops = 1 . 5 grammes have been used. The length of the operation is about an hour. After the reaction-mixture has stood a further quarter hour, it is removed from the freezing mixture and allowed to come to the room temperature. If, in consequence of a secondary reaction, the temper1 A. 281,25. TRANSITION FROM ALIPHATIC TO AROMATIC SERIES ature should go up to 200, the flask is cooled off a short time in ice water. The reaction-product is a viscous, bright yellow liquid in which numerous drops of water are' suspended. It is allowed to stand undisturbed until it solidifies to a crystalline mass, which generally requires from two to three days. A small specimen is pressed out on a porous plate and recrystallised from diluted alcohol. Colourless needles are thus obtained which melt at 79-80 0 . The solidification of the crude product may be hastened by seeding it, after one day's standing, with crystals obtained in a previous preparation. This is best done on the upper portion of the flask, which is only moistened by the liquid. 2. DIMETHYLCYCLOHEXENONE The crude product liquefied by heating in a water-bath is poured into a mixture of 400 grammes of water and 100 grammes of concentrated sulphuric acid contained in a round litre flask provided with a long reflux condenser. The reaction-mixture is heated to lively boiling on a wire gauze ; a few pieces of unglazed porcelain are placed in the flask to insure a Regular ebullition. After about seven hours' heating (the experiment should be commenced in the morning of a working-day), the reflux condenser is replaced by an ordinary condenser, and steam is passed into the mixture until the distillate measures about 100 c.c. The flask is heated by a free flame up to the boiling-point of its contents. The distillate is preserved in a well-closed vessel. On the second day the mixture is again heated for seven hours (with a reflux condenser, new porcelain scraps in the flask), and then 100 c.c. are. again distilled off with steam. This is repeated on the third day, and finally steam is passed into the mixture until from a test portion of the distillate saturated with solid potash no oil, or only a minute quantity, separates out. The three distillates in which the reaction-product is for the most part dissolved are now united. Solid potash is added until it is no longer dissolved. For the success of the salting out, one must use anhydrous potash 15-20 grammes. and the heating is continued until there is only a slight evolution of hydrobromic acid. under the aood. upon which only a small quantity of an oil should separate out. 3. It is separated from the water solution in a dropping funnel. Hydrobromic acid is evolved copiously. with frequent shaking. The reaction-mixture is then allowed to stand. Yield. s-XYLENOL A mixture. Boiling-point of the pure compound. to incipient ebullition of the acetic acid. using an air condenser. After cooling. . cooled by ice water. If the distillate be allowed to stand in a cool place over night. and the alcohol is distilled off by the aid of a Hempel tube 10 cm. long filled with glass beads. The portion going over between 200-215° is collected separately. about an hour on a waterbath to about 500. The by-products insoluble in the alkaline solution are extracted with a sufficient quantity of ether. on a wire gauze. or better over night. So long as the xylenol is coming over.nol liberated is distilled over in the presence of carbon dioxide with steam (use a three-hole cork). The mixture is heated. it is poured carefully into a cooled solution of 75 grammes of caustic potash in 150 grammes of water. until the evolution of hydrobromic acid almost entirely ceases. The end of the distillation may be readily determined. and the s-xyle. at least half a day. at the room temperature. a test of the distillate by adding a few drops of bromine will show a precipitate of tribromxylenol. 211°. It is heated finally. the temperature is then increased until the water boils.178 SPECIAL PART as pure as possible. of 10 grammes of the ketone dissolved in 20 grammes of glacial acetic acid (the acid must not be allowed to solidify) is treated gradually with a mixture of 13 grammes of bromine and 10 grammes of glacial acetic acid from a dropping funnel. From the potash solution a brownish red oily layer separates out: it consists of dimethylcyclohexenone and alcohol. the alkaline solution is saturated with carbon dioxide. The residue is dried over fused Glauber's salt and distilled from an ordinary fractionating flask. and the filtrate saturated with solid salt and extracted with ether. with compounds containing the group CH2 between two negative radicals (acetacetic ester. 64°.CH . Equal molecules unite in accordance with the following equation: Example: CH. malonic ester. 5-6 grammes. There are thus obtained colourless needles of tribromxylenol. A better characterisation of this phenol is obtained by covering a few drops of it in a test-tube with 5 c.c.CH . Yield. 220-221°. cc :OOC 2 H 5 Ethylideneacetacetic ester i. 1. in two ways. with the elimination of water. and others). Melting-point of s-xylenol. The excess Of bromine is removed by the addition of a solution of sulphur dioxide. Boiling-point. the crystals are filtered off. acetylacetone. The reaction may take place between one molecule of the aldehyde and two molecules of the other compound: X R X X R X CH [H| + CH |O + H|HC = H2O + CH .TRANSITION FROM ALIPHATIC TO AROMATIC SERIES 179 the larger portion of the xylenol will crystallise out. In order to obtain the portion remaining dissolved. The precipitate is recrystallised from alcohol. Aldehydes unite. which melt at 1650. of water and then adding bromine drop by drop until the reddish brown colour of the latter does not disappear. For bringing about the first reaction the following-named substances may be used as condensation agents: hydrochloric acid. ) . and others).CH - COOC2H5 COOC2H5 COOC2H5 COOC2H5 Ethylidenebisacetacetic ester. acetic anhydride. diethyl amine.R Y I B . 31.l8o SPECIAL PART Example.CH = NRX + H2C = I^NH. It is probable that the amine reacts first with the aldehyde.) In the example above: /IN (^rij^j CH3. For the second reaction the bases mentioned may be used. piperidine. amine ^r LM1NR =RCH \NR" +H2O (R" = a bivalent radical or two univalent radicals. 738. = CH 3 . A small quantity of one of these may produce large quantities of the condensation product: this is a case of a so-called continuous reaction. + C =CH. C H 1 + s H N ( C j H . Y . as well as primary and secondary amines (ethyl amine. water being eliminated:* prim. CH< O + H2O X ^ N(C 2 H 5 ) 2 The aldehyde derivative thus formed then acts upon the second compound with the regeneration of the amine: X X R. carried out in practice: CH3 CO CH3 CH 3 CO CH 3 CO CH8 CH3 CO CH C H [ H 1 + C H [ 0 T H 1 C H = H2O + CH . six-membered carbon rings are formed as follows: X .OOC .5 diketones) and in addition a methyl group.CH . Of the compounds which can be obtained by reaction (2). C H -.CO CH3. #of especial interest are those which.CO X -CH -CO R.dH XXH-C 0 ^:H -CH8 = H2O + R.CO = H 2 O+ -CH CH 8 XH CH QH. X -CH ) -c-c H In the above example: C2H5OOC .CH . and so on.CH . 2.C ~CH-C-CH8 . like the ethylidenebisacetacetic ester prepared above.TRANSITION FROM ALIPHATIC TO AROMATIC SERIES l 8 l X R H CH = 2 H N R n + CH . contain two carbonyl groups (1.CH In the above example: CH* OOC2H5 = 2 NH(C 2 H 5 ) 2 + CH .(5H C2H5OOC .CH .CH COOC2H5 COOC2H5 The amine thus regenerated carries over anew the aldehyde residue to the acetacetic ester. If such compounds are treated with those substances which have the power to eliminate water (alkalies or acids).CH . H. CH 3 CO. e. etc. etc. otherwise the elimination of water cannot take place. R = H. The compounds so obtained are all derivatives of the mother substance: CH 2 .CO CH vCHo . acetylacetone.CH C2H5 OOC. a second reaction takes place in the experiment made above.CH COOC. The many-sidedness of the reaction is materially increased by starting with the unsymmetrical 1. By using formaldehyde. benzaldehyde. The sulphuric acid saponifies the primarily formed acidester.CH-C~CH 3 C. and which may be considered as the keto-derivative of tetrahydrobenzene CH 2 . proprionaldehyde. C6H5. etc.CH-CO CH2-CO CH CH 3 . CCH5CO.CH . benzoylacetone..CH-CH HO \ S CH = 2CO 2 +2C 2 H 5 OH + CH 3 ~(fH \ CH 2 -C-CH 3 Dimethylcyclohexenonc This ring closing with 1.: CO R CO CH .5 diketones is capable of many modifications.CH 2 2 2 CH CH2-CH .5 diketone. with the elimination of carbonic acid: HO H OOC.182 SPECIAL PART Beside this ring closing. C:OOC 2 H 5 The nature of the reaction requires. C2H5. X = COOC2H5.CH H which is called cydohexenone.g. CH3. however. acetaldehyde. etc By using acetaceticester. that one of the two carbonyl groups must be connected with a methyl group.. eg. CH CH2 = Hexahydroxylene CH. e.CH3 If the hexahydrogen addition alcohols be treated with substances having the power to eliminate water.CH2 CH 3 . This primarily obtained compound may by different reactions be converted into other hydroaromatic and aromatic substances.CH3 If in compounds like hexahydroxylenol. at the same time the double union is severed.CH CH 3 . It is thus evident that the syntheses of a great variety of hydroaromatic compounds are possible.CH CH 2 CHg. the hydroxyl be replaced by iodine. therefore. ..CH . the dimethylcyclohexenone be reduced. OH CH2 . and the resulting iodide reduced. is a transition from the aliphatic to the (hydro) aromatic series. and two hydrogen atoms are added on. so that there is obtained an alcohol derivative of hexahydro-benzene or -xylene.CH.CH — J. and a keto-derivative of a hexahydroxylene is formed : CH2 .2 — V^XJL Hexahydroxylenol If this compound be oxidised. .TRANSITION FROM ALIPHATIC TO AROMATIC SERIES 183 This. the ketone group is converted into the secondary alcohol group. : CH2 . CHo .: CH2 .g.CH CH 2 CH2 . e. there is obtained a tetrahydrogen addition product of the hydrocarbon.CO CH 3 .g.~CH. If.CH CH. CH CH = Tetrahydroxylene CH2-CH. the secondary alcohol group is changed to a ketone group. there is obtained a hexahydrogen addition product of the hydrocarbon. VII Ed. and 24. II. II Ed. By these reactions the compounds of the pure aromatic series may be reached...C CH CH. p. Richter.CH 3 CH2 . Vol. OH CH = C CHo.. If bromine be allowed to act on the primarily arising ring compound. II Vol. p. Meyer-Jacobson. and the s-xylenol is obtained. the double union is broken up by the addition of two atoms of bromine: CH2 .(fH These dibromides are very unstable. 4.C .CBr .CO Finally. as has been done practically.? p. OH).SPECIAL PART 3. CH For further information concerning the transition from aliphatic to aromatic or hydroaromatic compounds.CH CH2 . pp. and even in the cold give off two molecules of hyclrobromic acid: CO CH2 .CO CHS. Krafft.CO) changes itself into the stable enol-fonn (CH = C .CH3 ^ H + Br2 = CH3. 440. this unstable keto-form (CH2 . compare Bernthsen. 79. VII Ed. 5.CO ^HBr CH2 . . 336. it is placed in a dry flask. 9. 206-207°. 47.Nitrobenzene and Dinitrobenzene 1 Nitrobenzene To 150 grammes of concentrated sulphuric acid contained in a J-litre flask. 12. and with frequent shaking. consisting of sulphuric and nitric acids.4). The nitrobenzene is then agitated in the funnel several times with water: it must be borne in mind that the nitrobenzene now forms the loiver layer. 60-70 grammes. Boiling-point. After cooling. the operation is interrupted. by immersion in water. with frequent shaking. If the temperature should rise above 50-600. milky at first. it is then heated in a water-bath for an hour at 6o* (thermometer in the water) . 10 grammes of nitrobenzene are 1 A. 98. 305. Ostwald's Klassiker der exacten Wissenschaften Nr. REACTION: NITRATION OF A HYDROCARBON EXAMPLES : . the lower layer. After being washed. 1. 100 grammes of concentrated nitric acid (sp. AROMATIC SERIES 1. Yield. becomes clear.II. and warmed on a waterbath with calcium chloride until the liquid. When all of the benzene has been added. a vertical air condenser is attached to the flask. It is finally purified by distillation from a fractionating flask provided with a long air condenser. is separated from the upper layer of nitrobenzene in a separating funnel. After cooling the mixture to the room temperature. add gradually. Dinitrobenzene To a mixture of 25 grammes of concentrated sulphuric acid and 15 grammes of fuming nitric acid. gradually add 50 grammes of benzene. . gr. during the heating the flask is frequently shaken. and the flask immersed in water for a short time. 1 If. .. CH 2 . the nitration under the above conditions always affects the benzene ring. 90 0 . Recently the nitro-group has been introduced directly into the sidechain. with frequent shaking. Since the benzene carbon atoms are in combination with only one hydrogen atom. or nitric acid and glacial acetic acid. (NO 2 ) 2 + H 2 O. If a compound is very easily nitrated. pressed out on a porous plate. C(. e. the nitro-compounds obtained on nitration are tertiary. Meltingpoint. Not only can the mother substances. If a substance is moderately difficult to nitrate. nitrolic acids.. NO 2 + H2O. aldehydes. the nitration may be effected. with stirring. glacial acetic acid is frequently used for this purpose.H5. i.g. undergo similar reactions. But the nitration does not take place in every case with the same ease. according to the conditions. it is added 1 B. and recrystallised from alcohol. In each case. therefore. or pseudo-nitroles. C6H5. C 6 H 5 . the most favourable conditions for the experiment must be determined. 10-12 grammes. the aromatic hydrocarbons. NO2 + NOo. the reaction-mixture is then heated for half an hour on a water-bath. NO 2 . etc. and then treated with nitric acid.186 SPECIAL PART gradually added (hood) . Re£ 194 and 198. toluene or ethyl benzene be heated with weak nitric acid (sp. The property of yielding nitro-derivatives. The dinitrobenzene which solidifies is filtered off. OH = CCH-. or phenylnitroethane. and not the side-chain. after cooling somewhat. they therefore do not have the power to form salts. one or more nitrogroups can be introduced at the same time. CH . amines. acids. as phenols. into cold water. OH = C 6 H 4 . the substance is added to a mixture of nitric acid and water. but all their derivatives. it is poured. Yield.e. gr. or the substance may be dissolved in a solvent which is not attacked by nitric acid. CH3 is obtained. by nitric acid diluted with water. If a saturated aliphatic residue is present in an aromatic compound. The above reactions take place in accordance with the following equations: C6H6 + NO 2 . NO 2 . phenylnitromethane. According to the conditions under which the nitration is carried out. like the primary and secondary nitro-compounds. 27.076) in a bomb up to about ioo°. The reverse process may also be employed. when treated with nitric acid. is a characteristic of aromatic compounds. 1. washed with water. only result in the formation of one mononitrobenzene. (2) the quantity of nitric acid may be varied. there are formed: N0 * and . The introduction of one nitro-group in the benzene molecule can. the theoretical amount of nitric acid. the substance may either be added to the mixture of nitric acid and sulphuric acid. the nitro-derivatives of the hydrocarbons are indifferent compounds like the hydrocarbons. or in water. In order to determine which of these numerous modifications will give the best results. If an alkyl radical is present in the benzene molecule.and para. the following laws are of general application. e. this will be considered under the next preparations. or an excess. preliminary experiments on a small scale must be made. by gentle heating. The nitration can be-effected in a freezing mixture. in ice. If a nitro-group is introduced into a compound of an acid nature like phenol.g. e. at the boiling temperature. may be used. Thus. or the nitric acid is added to the substance dissolved in concentrated sulphuric acid. it becomes more strongly acid. or difficultly soluble. the nitro-groups enter the ortho.AROMATIC SERIES 187 to concentrated or fuming nitric acid. they can be separated from the nitrating mixture by diluting it with water. at times either potassium nitrate or sodium nitrate may be used instead of nitric acid. or in many cases better. The great importance of the nitro-compounds is due to their behaviour on reduction. e. In working with sulphuric acid solutions. If the nitration is difficult. Since the nitro-compounds are generally insoluble in water. obviously. Further.g. The chemical character of a substance is not changed in kind. nitro-aniline is less basic than aniline. the nitro-phenols are more strongly acid than phenol.. with a solution of common salt. or finally. The three nitration methods just described may be still further modified in two ways: (1) the temperature may be varied. but in degree. Concerning the introduction of the nitro-group.g. On nitrating toluene. In the nitration. the elimination of water is facilitated by the addition of concentrated sulphuric acid to ordinary or fuming nitric acid. When a nitro-group is introduced in a basic compound.but not the meta-position to the radical. by the introduction of a nitro-group. the resulting substance is less basic. in part solids.283. e. Thus. or cyanogen-group. . and benzonitrile give on nitration respectively: CHO CO. O-nitrotoluene or o-nitrophenol yield on nitrating: respectively.. Benzaldehyde. in case these latter distil without decomposition.188 SPECIAL PART The nitro-groups seek the same position when a benzene-hydrogen atom has been substituted by hydroxyl. a second one will take the meta-position to this. To this are gradually added 200 grammes of concentrated hydrochloric acid 1 A . carboxyl-. OH The nitro-compounds are in part liquids. on nitrating nitrobenzene. Thus. 2. On the other hand.and p-nitrophenol. REACTION: REDUCTION OP A NITRO-COMPOUND TO AN AMINE EXAMPLES: ( I ) Aniline from Nitrobenzenel (2) Nitroaniline from Dinitrobenzene A mixture of 90 grammes of granulated tin and 50 grammes of nitrobenzene is placed in a 1^--litre round flask. on nitration the nitro-group goes in the meta-position to this.g. 44. they possess a higher boilingpoint than the mother substance. From m-nitrobenzoic acid the following dinitrobenzoic acid is formed: CO. m-dinitrobenzene is formed. benzoic acid. OH If a compound already contains a nitro-group. phenol gives on nitration a mixture of o. if a compound contains an aldehyde-. and becomes clear. For the reduction of every nitro-group. The second tenth of the acid is then added. and the above operation repeated. the mixture is finally heated one hour on the water-bath. a long condenser is attached to the flask. Yield. before a farther addition of caustic soda. so that the heat of neutralisation may be utilised. and steam is passed into the hot liquid. After a short time it becomes warm. the ether is evaporated and the aniline subjected to distillation. As soon as the distillate no longer appears milky. the aniline collecting under the water. 1820. an air condenser. as a colourless oil.c. and the distillation with steam immediately following.AROMATIC SERIES 189 in the following manner: At first only about one-tenth of the acid is added. the reaction becomes less violent. then a solution of 150 grammes of caustic soda in 200 grammes of water is gradually added. may take place within a short time. treated with 25 grammes of finely powdered sodium chloride for every 100 c. not too narrow. the flask is immersed in cold water until the reaction has moderated. After one half of the acid has been used. of the liquid. the warm solution is treated with 100 c. To separate the free aniline.c. upon which aniline. After the ethereal solution has been dried by treating it with a few pieces of solid potassium hydroxide. is then attached to the flask and the mixture well shaken. If the circumstances are such as not to permit the experiment to be completed without interruption. of water. the receiver is changed and about 300 c. As soon as this happens. and the aniline extracted with ether. In order to effect the reduction of the nitrobenzene completely. and water pass over. Boiling-point. and the second half may be added in larger portions. To the nitro-compounds of the aromatic series. as well as those of the aliphatic series. . 90-100% of the theory. the flask is cooled by water for a short time. shaken until all the salt is dissolved. and finally an active ebullition takes place. more of the liquid distilled over. If the action of the caustic soda causes the liquid to boil.c. belongs the property of being converted into primary amines on energetic reduction. it is so arranged that the neutralisation with sodium hydroxide. The distillates are mixed. When all of the solution has been added. the liberated amine is driven over with steam. as the reducing agent. like ether. as in the above example. and insoluble in alkali. and the reaction-mixture dissolves clear in water. granulated tin and hydrochloric acid..e. it is advisable to precipitate the tin before liberating the amine. NH 2 + 3 SnCl4 + 4 H2O. To 1 molecule of a mononitro-compound. But this process is often troublesome. NO. this is separated from . This is done by diluting the acid solution with much water.I90 SPECIAL PART six atoms of hydrogen are necessary. heating on the water-bath. If the reduction is to be effected by metallic tin. but into stannous chloride: C6H5. + 3 SnCl2 + 6 HC1 = C(. which subsides with great difficulty. i. In this case. and the amines unite with it to form soluble salts. If. double the above quantity is frequently used. NH2 + 3 SnCl4 + 2 H2O. solution forms an emulsion with ether. the end of the operation occurs when no more of the insoluble nitro-compound is present.H5. In many cases. until the oxide of tin which separates out at first is redissolved in the excess of alkali. the tin is not converted into stannic chloride. are therefore used. NO2 + 3 H2 = X . volatile or non-volatile amines can be extracted from an alkaline solution by a proper solvent. then the acid solution is treated with caustic potash. In calculating the amount of the latter necessary for a reaction. various methods may be employed. hydrochloric acid is always present in excess. and the following equation is the general expression of the reaction: X. NO2 + 3 Sn + 6 HC1 = CCH5. NO2 + 3 Sn + 12 HC1 = 2 CCH5. hydrogen sulphide is passed into it. NH 2 + 3 SnCl2 + 2 H2O Since. or 3 molecules of stannous chloride. Further. where a non-volatile amine is under examination. in the cases mentioned. For the reduction of nitro-compounds on the small scale in the laboratory. In order to get the free amine from the acid mixture. the amine is volatile with steam. and as soon as the liquid has reached the temperature of the bath. The tin is precipitated as stannous or stannic sulphide. or caustic soda. it is to be remembered that the salt crystallises with two molecules of water (SnCl2•+ 2 H 2 O). since the alkaline tin . or stannous chloride and hydrochloric acid: (1) 2 C6H3. it is most convenient to use. 3 atoms of tin. it may be obtained by filtering off the alkaline liquid. 1J atoms of tin. If the free amine is solid. (2) C6H5. NH 2 + 2 H2O. to 1 nitro-group. a small quantity of which is always used on the large scale. obviously. NO2 + 3 Fe + 6 HC1 = 3 FeCl2 + 2 H2O + C6H5. reduction of nitro-compounds. slaked lime is employed in preference to the more costly alkalies. NH2 + 2 Fe(OH) 3 For the neutralisation of the hydrochloric acid. if necessary. is used in the preparation of bases like aniline. these cannot be separated 'by the use of an alkali. it is frequently necessary to drive off the excess of the acid before treating with hydrogen sulphide. In the laboratory. This is done by evaporating to dryness on the water-bath. a-naphthyl amine. which. the acid solution evaporated to dryness. etc. as in the above example. the tin is always removed first. zinc. After the tin sulphide has been filtered off. the isolation of the amine may be facilitated by filtering it off. according to the equation: CCH5. If one is dealing with amines... on the large scale. the reduction should theoretically take place in accordance with the following equation: C6H6. much less hydrochloric acid (only 3^) is used than that required by the above equation. NH2. other metals. is precipitated only with difficulty by hydrogen sulphide. and pressing out on a porous plate. or the amine hydrochloride combines with the tin chloride to form a difficultly soluble double salt. sodium carbonate. and the amido-compound is now liberated by the addition of sodium acetate. in connection with an acid.AROMATIC SERIES 19I the amine hydrochloride by filtering. possess an acid character. like amidoacids. In a case of this kind. At times. NO2 + 2 Fe + 4 H2O = CGH5. the amine forms with hydrochloric acid. are only rarely used in the place of tin or stannous chloride. if it should be present. a portion of the filtrate is tested with hydrogen sulphide for tin. owing to its cheapness. Since tin. the nitro-compound is reduced by the iron without the action of hydrochloric acid." As a matter of fact. In the presence of ferrous chloride. washing with hydrochloric acid. a difficultly soluble salt. in the presence of a large excess of hydrochloric acid. sodium hydrogen carbonate. to remove the hydrochloric acid. from the corresponding nitrocompounds. then diluted with water. With amido-phenols. By the use of iron and hydrochloric acid. like iron. etc.. the whole filtrate is evaporated on the water-bath. toluidine. or sodium sulphite may be used to decompose the hydrochloric acid salt. On the large scale. as completely as possible. . iron. In this case. and hydrogen sulphide is again passed into it. for the. provided with a reflux condenser. which may be generally used for the reduction. is heated for about half an hour on a water-bath. This operation is repeated until there is an increase of 0. (B. dinitrohydrocarbons may be converted into nitro-amines. treated with ammonia. the current of hydrogen sulphide is then shut off.192 SPECIAL PART The complete reduction of nitro-compounds containing several nitrogroups is conducted in the same way as for mononitro-compounds.8 gramme of concentrated ammonia for 1 gramme dinitrobenzene (the ordinary dilute solution of ammonia employed as a reagent must not be used). of compounds containing several nitro-groups. it is then treated with 0. which is well cooled. the mixture is saturated with hydrogen sulphide at the ordinary temperature. for cases of this kind.6 gramme in weight for every gramme of dinitrobenzene used.) EXPERIMENT I 1 The recrystallised dinitrobenzene is dissolved in alcohol (4 grammes alcohol to 1 gramme dinitrobenzene). 2161. If it is desired to reduce but one or two of several nitro-groups. is this: An alcoholic solution of the theoretical amount of stannous chloride saturated with hydrochloric acid is gradually allowed to flow into an alcoholic solution of the substance to be reduced. and the flask. For this purpose. It is then allowed to cool to the ordinary temperature.g. If in consequence of insufficient cooling the required increase in weight does not take place. it cannot be done by adding just the calculated amount of the reducing agent. After the flask and its contents have been tared. according to circumstances. and hydrogen sulphide passed into it. step by step. or it is heated in a water or alcohol solution with a previously prepared water or alcohol solution of ammonium sulphide. in a flask. A second method. and hydrogen sulphide agiin passed into it to saturation. special methods are necessary.. e. hydrogen sulphide in the presence of ammonia or ammonium sulphide is often used for the reduction: H2S = H 2 + S The compound to be reduced is dissolved in water or alcohol. 19. In this way. hydrogen sulphide 1A. upon which a portion of the dinitrobenzene separates out. 176 44. and constantly shaken. heated. . etc. the solution is quickly cooled down. o-nitrocinnamic acid to o-amidocinnamic acid. etc. Yield. or colourless solids like • p-toluidine. and difficultly soluble in water. They will be referred to under the different preparations. By this reaction. xylidine. the precipitate filtered off. 1B.g.. and much more readily soluble in water than the mon-amines. o ..H2 The reduction is effected by adding to the substance to be reduced. e. e. an aldehyde-group.1323. pseudocuminidine. 28. or barium-hydroxide). In cases of this kind. The primary mon-amines are in part colourless liquids. It reacts with water in accordance with this equation: A1 + 3 HOH = A1(OH)3 + 3 H Besides the reducing agents mentioned. ferrous hydroxide is frequently used: 2 Fe(OH) 2 + 2 H2O = 2 Fe(OH) s -I.AROMATIC SERIES 193 is again passed into the mixture. o-nitrobenzaldehyde is reduced to o-amidobenzaldehyde. and extracted several times by warming with dilute hydrochloric acid. aniline. there is still a large number of others which find only an occasional application in reducing nitrocompounds to amines. They can be distilled without decomposition.g. From the acid filtrate. It is then diluted with water. aluminium amalgam1 is recommended. 114 0 . which appears to be well adapted for a great variety of reduction reactions. washed with water. it is recrystallised from water. a weighed quantity of ferrous sulphate. the naphthyl amines. which have been slightly acted on by caustic soda. As a perfectly neutral reducing agent. in the presence of an alkali (potassium-. etc. non-volatile with steam. sodium-. /NO2 /NO2 C6H4<^ + 3 H 2 S=C 6 H 4 <Q +2H2O + S 3 Special methods are necessary for the reduction of nitro-compounds containing groups capable of being acted upon by hydrogen. 70-80% of the theory. It is made by treating aluminium filings or shavings. an unsaturated side-chain.and poly-amines are for the most part solids. Meltingpoint. The di. are volatile with steam. o-toluidine. with a solution of mercuric chloride. the nitro-aniline is set free by neutralising with ammonium hydroxide. and shake the mixture. and extract the nitrobenzene with a little ether. but a dirty violet precipitate separate out. In a test-tube mix 5 drops of "concentrated sulphuric acid with 5 drops of concentrated nitric acid. of concentrated hydro- . by this reaction (Runge's). the aniline water is diluted further. of water. of this aniline solution with 10 c. At moderate temperatures.c. If in this experiment the solution should not remain clear. and the ether evaporated. If a salt of aniline is to be tested.HNO3 .ig4 SPECIAL PART The amines possess a basic character.c.NH2. Aniline sulphate Like ammonia. in consequence of the negative nature of the phenyl group. for this reason they must not be dried with this substance (see page 47).H2SO4 . Aniline nitrate (C6H5. it is dissolved in water. this latter evaporated. . . . . A violet colouration takes place. This reaction may also be used to detect small quantities of benzene or nitrobenzene. and the experiment repeated. The primary mon-amines find numerous applications in the laboratory. and the residue dissolved in water. the following experiments are made: (1) Add 3 drops of aniline to 10 ex. in consequence of their great activity. then add 1 drop of benzene. as well as on the large scale. the free aniline extracted with ether. Then proceed exactly as just directed. Salts: C6H5. The aniline dissolves. With the aniline prepared above. and add a small quantity of a filtered water solution of bleaching powder.c.NH2)2. Frequent reference will be made to the subject in the following pages. and warm gently by passing the tube through a flame several times. but the basicity is weaker than that of the aliphatic amines.c. . treated with alkali. Aniline hydrochloride C6H5. The residue is treated with 1 c. (2) Dilute 1 c. shake. 1 part of aniline dissolves in about 30 parts of water. Then add 5 c. the ether layer is removed with a capillary pipette. of water. the most minute quantity of free aniline may be detected. HC1 . NH2. a too concentrated solution has been used. the amines unite with calcium chloride to form double compounds. of water in a test-tube. . disagreeable odour. the isonitrile reaction will show the presence of any primary amine of the aliphatic or aromatic series. add 2 more drops of the dichromate. and to this is added a piece of zinc the size of a lentil. this is recognised not only by the separation of potassium chloride.AROMATIC SERIES 195 chloric acid. If it is desired to determine whether a given compound is nitrobenzene. While the two colour reactions with bleaching powder and chromic acid are used especially for the recognition of aniline. The odour becomes more pronounced on pouring off the liquid and adding some cold water to the tube. If the reaction does not take place. Then add 4 drops of an aqueous solution of potassium dichromate. remove it by rubbing it against the walls of the dish. NH2 + CHCI3 = C6H5. (3) In a small porcelain dish place 5 drops of concentrated sulphuric acid. until the hydroxide of zinc precipitated at first is redissolved. of alcohol. After a short time the liquid assumes a beautiful blue colour. If the vapours of the isonitrile are inhaled through the mouth. (4) Isonitrile Reaction : Heat a piece of caustic potash the size of a bean with 5 c.c. but by a most highly characteristic. NC + 3 HC1 . The reaction takes place in accordance with the following equation: CfiH6. or heat a moment over a small flame. or on gentle warming. the mixture is diluted with water. The aniline sulphate thus formed solidifies for the most part on the rod. to effect the reduction. a peculiar sweet taste is noticed in the throat. and made strongly alkaline. it is at once reduced with zinc and hydrochloric acid. pour off the solution from the undissolved residue into another test-tube. A reaction takes place immediately. and with a glass rod add 1 drop of aniline. The reaction must be carried out under a hood -with a good draught. When the zinc is dissolved. Then proceed as just described. and mix the liquid by revolving the dish. the aniline is then extracted with a little ether. the warm solution is treated with 1 drop of aniline and 4 drops of chloroform. .CO.C=N. before the water is poured on the residue. of water at 40 0 . C 0 H 5 . In the course of an hour add gradually in small portions. e.196 SPECIAL PART For the elimination of hydrochloric acid. it is then filtered. with good shaking. the filtrate (solution I) is poured into a beaker. on the one hand the smallest quantity of a primary base may be detected by this reaction.NH 2 + H . using suction and a Blichner funnel. CN + 2 H2O = C6H5. Since all isonitriles or carbylamines possess a characteristic odour. The isonitriles are isomeric with the acid-nitriles. After the reaction is complete. the mixture is frequently shaken and allowed to stand for about ten minutes at the same temperature . REACTION: (a) REDUCTION OP A NITRO-COMPOUND TO A HYDROXYLAMINE DERIVATIVE. the suction is disconnected from the funnel. the isonitriles decompose into a primary amine and formic acid : CGH5.NC + 2 H2O = C 6 H 5 . OH 3. While the nitriles on saponification give acids. of water with 10 grammes freshly distilled nitrobenzene. CO. OH + NH 3 C6H5.N=:C::::. .c. and on the other a base may be shown to be primary. from the zinc oxide. and is only attached after 1 Modified in accordance with the kind suggestion of Professor Bamberger. and the zinc oxide deposit on the funnel is washed with 200 c. In the isonitriles it is very probable that the carbon atom combined with the nitrogen atom is only bivalent: C6H5.c. caustic potash is added. Zurich. Secondary and tertiary bases do not give the reaction. 15 grammes of zinc dust.g. benzonitrile. (J) OXIDATION OF A HYDROXYLAMINE DERIVATIVE TO A NITROSO-COMPOUND EXAMPLES : (a) Phenylhydroxylamine from Nitrobenzenel (3) Nitrosobenzene from Phenylhydroxylamine (a) Phenylhydroxylamine: In a thick-walled J-litre flask treat a solution of 5 grammes of ammonium chloride in 160 c. during this operation the temperature is held constantly between 140 and 160 (thermometer in the liquid) by immersing the flask from time to time in ice water. Precautions: In the preparation of phenylhydroxylamine. care must be taken not to breathe in any of the dust. The two water solutions are separately cooled in ice water and saturated (with stirring) with finely pulverised salt. 356). Use only a gentle suction (solution II). and soon the nitrosobenzene sublimes in white. well cooled by ice water. from coming in contact with the skin. steam should be passed into the oxidation liquid. are pressed out on a porous plate. a few moments later beautiful emerald-green oil drops appear which . since it causes very painful and annoying inflammation.c. Yield. without further purification. The success of the reaction depends essentially upon the quality of the zinc dust used. and particularly a warm solution of it. almost quantitative. Even in pressing it out or pulverising it under the hood. 8r°. about 45 grammes.c. Zinc dust of 75 % is referred to above. the pure nitrosobenzene separates out immediately in crystals. lustrous plates in the bent tube entering the condenser. {b) Nitrosobenzene:* To a solution of 30 grammes of concentrated sulphuric acid in 270 c. add 4 grammes of freshly prepared and finely pulverised phenylhydroxylamine. care is taken to prevent it. and.AROMATIC SERIES 197 there has been time enough for the phenylhydroxylamine to be dissolved. for solution I. The colourless crystals separating out are filtered off with suction. Melting-point. of water. of water. A small test-portion of the crude product is recrystallised from benzene. about 60 grammes of salt will be required. since it causes extraordinarily violent attacks of sneezing. without washing. the solution is then quickly treated with an ice-cold solution of 4. and for solution II. the total quantity of nitrosobenzene is carried over in 4-5 minutes. " On account of the splendid phenomena. It is therefore necessary to make a zinc dust determination (see p. is worked up into nitrosobenzene. The remainder.6 grammes of potassium dichromate in 200 c. and then use about 10% more than is required by the theory. At the beginning of the heating the walls and neck of the flask take on a deep green colour. NH 2 X)H Nitroben2ene Nitrosobenzene Phenylhydroxylamine Aniline Phenylhydroxylamine1 was obtained simultaneously by Bamberger and Wohl by the reduction of nitrobenzene with zinc dust in a neutral solution: C6H5NOo -f 2 2n + H.1432. 3 B. to snowwhite crystals. Recently two classes of compounds have been discovered which appear to be intermediate products between the nitro-compounds and amines.5-68 0 . but a hydroxyl group enters the para position (to the amido-group) if it is vacant.1R.C6H-N< —>. If it be warmed with mineral acids.. cotton plug." (a) The primary amines discussed in the preceding reaction are the lowest reduction products of nitro-compounds.0 = C G H 5 N / + 2 ZnO The presence of certain salts.1927. . Thus from nitrobenzene p-amidophenol is obtained.C 6 H 5 . e. it undergoes a noteworthy transformation into paraamidophenol: —^C6H/ 2 X)H This behaviour explains the electrolytic reduction of aromatic nitrocompounds. 245.12J8. 2810.I98 SPECIAL PART solidify so completely. they may be called " monomolecular intermediate reduction products. 28. 27. T h e crystals of nitrosobenzene are pushed out of the condenser with a glass rod.27. Phenylhydroxylamine acts like a base towards acids.1844. N O 2 — ^ C6H5.2 If a nitro-compound dissolved in concentrated sulphuric acid is subjected to electrolytic reduction. In accordance with our present knowledge the reaction is .3040.1347. NO —>. that the distillate presents the appearance of a faintly green liquid containing only a few minute crystals. 29. 26.g. the end being covered with a." /H C6H5. calcium or ammonium chloride. in the lower part of the condenser. Melting-point 67. spread out on a porous plate and washed upon the plate with ligroin (boilingpoint 40-70 0 ). In order to distinguish them from the compounds referred to in the next preparation.1548. not only is the nitro-group reduced to the amido-group. promotes the reaction. g. Azobenzene. 15. C(5H5 + H2O Combined with hydroxylamine they form isodiazo-compounds. N / ) C H . e. N/ / + O = C 6 H5 . more energetic oxidising agents convert it into nitrosobenzene..NO + H2O The nitrosohydrocarbons in the solid state form colourless crystals.. e.pr. With primary amines they combine to form an azo-compound. B. . REACTION: REDUCTION OP A NITRO-COMPOUND TO AN AZOXY-. 36.-1 To 200 grammes of methyl alcohol contained in a 2-litre flask provided with a wide reflux condenser. (£) Nitrosohydrocarbons have not yet been obtained directly by reducing the nitro-compounds. On reduction they go over into amines. C e H 5 . CHO = CGH5.93. They possess a characteristic piercing odour which suggests quinone and the mustard oils ."'" "T^ Phenylhydroxylamine is a strong reducing agent. but when fused or in solution an emerald-green liquid. + NOOH = C 6 H 5 N< + H2O X)H X)H With aldehydes it reacts thus : CGH5. N< + C 0 H 5 . which immediately undergoes a molecular transformation into the amidophenol. but when hydroxylamine derivatives are oxidised they yield nitroso-compounds : C e H 5 . 20 grammes of sodium in pieces the size of a bean are gradually ij. 4 . AZO-. With nitrous acid it forms a nitroso-derivative: /H /NO C6H5N<. they are extremely volatile. Q H 5 + H2O By the oxygen of the air it is oxidised to azoxybenzene. N zz N .AROMATIC no longer considered remarkable. . which reduces' Fehling's solution and an ammoniacal solution of silver nitrate even the cold. C(5H5 = C(JH5. NO + H 2 N. Hydrazobenzene (i) Azoxybenzene . Phenylhydrojrylarnine is first formed.g. OR HYDRAZO-COMPOUND EXAMPLES : Azoxybenzene.865. (2) Azobenzene . after it has solidified.329. If solidification does not take place now. is further cooled with ice. and. and the difficultly volatile residue. From methyl alcohol (use 3 c. and the mixture heated for 3 hours on an actively boiling water-bath (reflux condenser). Yield. If. When the me^al is dissolved. the mixture is distilled from a small retort. The residue is treated with water. 207. the flask is not cooled (heat being generated by the reaction). are finely pulverised and intimately mixed in a mortar with 15 grammes of coarse iron filings. the experiment must be repeated. not tubulated. . 20—22 grammes. the size of the flame is increased after some time. It is first warmed with a small luminous flame kept in constant motion. and the reaction-mixture poured into a beaker. which is separated from the liquid by decanting the latter. melting at 36°. After long standing. this often causes a troublesome bumping.c. The greater portion of the methyl alcohol is then distilled off (the flask being placed in the water-bath. this is distilled off with steam. of the alcohol for every gramme of the substance) the azoxybenzene crystallises in bright yellow needles. Since methyl alcohol frequently contains much water. finally the last portions are distilled over with a non-luminous flame.2OO SPECIAL PART added. the oil at the bottom solidifies to a bright yellow crystalline mass. after it has cooled. 3 « . which must also be completely dry. dried completely by heating on a water-bath for an hour. the first portions of the sodium must not be added too rapidly. If the azoxybenzene does not solidify. it is washed several times with water and finally pressed out on a porous plate. on heating. silk thread). The reddish distillate is collected in a small beaker. a sudden but harmless explosion should occur. the main quantity of the water solution is poured off and the oil treated with small pieces of ice. is washed with hydrochloric acid to remove 1 A.-1 Five grammes of crystallised azoxybenzene. is. it is due to the presence of nitrobenzene. especially in a cool place. 30 grammes of nitrobenzene are added. Crystals of sodium formate soon begin to separate out. it is due to the fact that the substances were not dry. nitro-compounds undergo a partial reduction in such a way that two molecules enter into combination. in the form of coarse red crystals melting at 6&°.c.NO2 2 Mol. The two pressed-out crude products are united. 20 c. The experiment is repeated a second time with a fresh quantity of azoxybenzene. The hydrazobenzene precipitating out of the alcoholic solution is quickly filtered. after a partial evaporation of the solvent. then the azo-.NV CCH5-N C 6 H 5 . (3) Hydrazobenzene . the reaction takes place most surely by dissolving sodium in methyl alcohol as above. By crystallising from ligroin it is obtained pure. and pressed out on a porous plate. *868. Melting-point. which in order to distinguish them from the compounds obtained in Reaction 3 may be called u dimolecular intermediate reduction products. The hot solution is then filtered with suction (Biichner funnel) from the excess of zinc. washed with water containing sulphur dioxide.c. Nitrobenzene c 6 H 5 . . 437. Azo. of water are previously placed in the filter-flask. Azoxybenzene ~>- QH 5 -N 1 Mol. and treat with a solution of 2 grammes of caustic soda in 4 grammes of water. There are thus obtained first the azoxy-. then with water.N/ —>x Mol. 1 Mol. and pressed put on a porous plate. particularly.-1 Dissolve 5 grammes of azobenzene in 50 grammes of alcohol (about 95%) in a flask provided with a reflux condenser.NH_ n C6H5. either sodium amalgam or alcoholic-caustic potash or caustic soda is used. Yield." QH. 12 6°.— > benzene benzene w* Jinine In order to reduce a nitro-compound to an azoxy-compound.. The reducing action of sodium methylate depends upon the fact that it is oxidised tQ 1Z. With nitrobenzene. of a water solution of sulphur dioxide and 100 c.— > . and finally the hydrazo-compound. To the boiling solution gradually add zinc dust in small portions (best by occasionally removing the cork) until the orange-coloured solution becomes colourless: about 8 grammes of zinc dust will be necessary. 80-90% of the theory.AROMATIC SERIES 201 the aniline.Hydrazo.N02 C6H5. Azobenzene crystallises from ligroin. by working carefully the same retort can be used again. Under the influence of suitable reducing agents. On reduction they yield first the azo-compounds.OH + Na = CH 3 . C6H5 + FeO O Azo-compounds may also be obtained directly from nitro-compounds. but they are not volatile with steam. which.C 6 H 5 = C 6 H 5 . it is possible to break up the double or centric union of the benzene ring. and finally two molecules of a primary amine.N/ A few words may be said here concerning the relatively weak reducing power of previously prepared alcoholates. ONa In the operation carried out above the reaction is expressed by the equation: C 6 H 5 .C 6 H 4 . its oxygen atom is removed. 0 N a + 3 H0O C6H5. azoxybenzene is converted into its isomer oxyazobenzene: C 6 H 5 .OH O If an azoxy-compound is distilled'carefully over iron filings. NziN. in comparison with the extremely energetic action of a mixture of undissolved sodium and alcohol.NCX> + 3CH 3 . C 0 . N—N. In this case the alcoholate does not act as a reducing agent as above. With the aid of this. like the nitro-compounds.Nv 4C6H5. While the previously prepared alcoholates can generally only abstract oxygen. CO. but the hydrogen effects the reduction: CH3. and thus prepare hydrogen derivatives of benzene.Nz=N. and an azo-compound is formed: C6H6. and cannot be distilled without undergoing decomposition. since they are reduced by sodium amalgam or an alkaline solutipn of .ONa = 2 I > 0 + 3 H . then the hydrazo-compounds.to orange-red crystallisable substances. two hydrogen atoms of the methyl group being replaced by one atom of oxygen : CH 3 .N-N.0Na + H The azoxy-compounds are yellow. are of an indifferent character . C6H5 + Fe = C6H5.202 SPECIAL PART sodium formate. By heating with sulphuric acid. the mixture just referred to belongs to the class of very strong reducing agents. ONa + 0 2 = H 2 0 + H . C6H5 + O = CGH5.N 6 5 X)Na / X\ ONa Sodium stannate Azo-compounds may also be obtained by the oxidation of hydrazocompounds: C6H -. Zinc dust with caustic soda acts as follows: /ONa Zn + 2 NaOH = Zn< + EL \ONa They may also be formed on the direct reduction of nitro-compounds in alcoholic solution by zinc dust and an alkali. EXPERIMENT: A few crystals o£ azobenzene are heated in a test-tube to boiling. NH.N = N. By the reduction of an azo-compound. NH2 — NH2. NH.NO 2 + 4Sn \ X)Na = Na C6H5.C1. e. and especially with the intensely coloured azo-compounds. over a free flame. in contrast with the azoxy-. which again condenses to crystals on cooling The azo-compounds thus differ in their stability from the very easily decomposable diazo-compounds. CfiH5. this method is used practically on the large scale.AROMATIC SERIES 2O3 stannous chloride (sodium stannous oxide). The hydrazo-compounds are formed by the reduction of azo-compounds with ammonium sulphide or zinc dust and an alkali. are colourless.N || | 4 | QH5 . They are derived from hydrazine. in which one hydrogen atom of the two amido-groups has been replaced by a hydrocarbon radical. A red vapour is evolved. differing in this respect from the azoxy-compounds. The . which also contain the group N = N.g. C6H5 + H2O The azo-hydrocarbons are orange-red to red crystalline substances which can be distilled without decomposition. The latter reducing agent acts in accordance with this equation: / 2C 6 H 5 . but it is in combination with only one hydrocarbon residue and an acid residue. N = N . The hydrazo-compounds. a hydrazo-compound is first formed and finally an amine. NH 2 p-Diamidodiphenyl = Benzidine The molecular transformation takes place essentially in para position to the imide (NH) groups. on heating. di-acid primary base. that the hydrazo-compounds no longer possess a basic character. into azo-compounds and primary amines. after cooling. In order to show the presence of aniline. and the substance crystallised from hot water. C6H5 = NH 2 . since the azo dyes derived from it possess the important property of colouring unmordanted cotton fibre directly. they are converted into derivatives of diphenyl: l C6H5 . the colourless compound becomes red. the substance is shaken with water and the bleaching-powder test applied. J-1863. azobenzene being formed. On oxidation hydrazo-compounds pass over to azo-compounds. EXPERIMENT : A few crystals of hydrazobenzene are heated in a small test-tube to boiling. If the hydrazo-compounds are treated with concentrated acids like hydrochloric or sulphuric acids. N H . EXPERIMENT: Hydrazobenzene is covered with concentrated hydrochloric acid.93. The other half of the solution is treated with dilute sulphuric acid.424. C6H4. N = N . 2 C6H5 . The first representative of these dyes made was Congo Red. for most azo dyes the" cotton must first be mordanted. In consequence. prepared from the bisdiazo-compound of benzidine and naphthionic acid. 122 0 . and allowed to stand for about 5 minutes. C6H4. and half the solution is made alkaline with caustic soda: the free benzidine is extracted several times with ether. Leaflets of a silvery lustre are obtained. N H . in that it is a strong. It is prepared technically. C6H5 = C6H5." 1 J-pr-36. N H . the entire class of these dyes is called the. Melting-point.204 SPECIAL PART basic character of hydrazine is so weakened by the presence of the negative hydrocarbon residues. . C6H5 + 2 C6H5. « Congo Dyes. N H . the ether evaporated. upon which the difficultly soluble benzidine sulphate separates out Benzidine differs from hydrazobenzene. a reaction which takes place slowly but completely. The hydrazo-compounds decompose. NH 2 . It is then treated with water. under the influence of the oxygen of the air. 688.NH-~/ r ~^>--NH 'r~~K V-NH—<" / -CH3 CH3. 50 grammes of carbon disulphide.. CO. e. /NH 2 I /NH2 L \CH 3 Dianisidine Tolidine If. derivatives of o.^ V-NH 5 . * In such cases.N=N. 681.H In a wholly analogous manner. the para position to the imido (NH) group is occupied as. then the benzidine transformation cannot occur. in hydrazo-compounds.and p-amidodiphenyl amine are formed through the so-called "Semidine transformation. 26. 287. 50 grammes of alcohol. and 1 B. 699: A.g. in p-hydrazotoluene. from o-nitrotoluene and o-nitroanisol are prepared o-tolidine and dianisidine."1 \ CH 3 XO.AROMATIC SERIES NH /JN 2 C 6 H 4 . 97.C 10 H 5 <( I \SO 3 H 205 C6H4. N H . . /CHS yOCH 3 Q.C10H5<( \SO. REACTION: PREPARATION OP A THIOUREA AND A MUSTARD OIL FROM CARBON DISULPHIDE AND A PRIMARY AMINE EXAMPLE : Thiocarbanilide and Phenyl Mustard Oil from Carbon Disulphide and Aniline Thiocarbanilide: A mixture of 40 grammes of aniline.1 — \NH. p-Scmidine 5.N=N. respectively. Z. The salt is decomposed. Meltingpoint. then with dilute hydrochloric acid. which melt at 1540. These are filtered off. with the addition of caustic potash. and alcohol (40 grammes of each) placed in a flask provided with a reflux condenser is heated. 2220. The distillate is treated with an equal volume of water. . 1869. after it has been dried on the water-bath. and treat with 120 grammes of concentrated hydrochloric acid. and then allowed to stand for several hours. on a sandbath. If a mixture of equal parts. and warmed with some dilute caustic soda solution. although a longer time is required. the distillation is discontinued. Yield. Phenyl Mustard Oil:1 In a flask of about 400 c. 589. Large. 1 B. carbon disulphide. of aniline. the mixture is distilled by heating to the boiling-point of the acid. and the free base obtained. almost quantitative yield of thiocarbanilide is obtained. to gentle boiling on the water-bath for 10-12 hours. dried with a little calcium chloride. of water. In order to obtain pure thiocarbanilide. a better. when colourless crystals of triphenylguanidine hydrochloride separate out. with a large flame under a hood. After the heating. the residue treated with water. 30-35 grammes. 986.c. Triphenyl Guanidine : The residue remaining in the flask after the distillation with hydrochloric acid is treated with 100 c. colourless tablets are thus obtained. Boiling-point. The excess of carbon disulphide and alcohol is then distilled off. For the preparation of phenyl mustard oil.206 SPECIAL PART 10 grammes of finely pulverised potassium hydroxide is gently boiled for 3 hours on a water-bath in a flask provided with a long reflux condenser. the crystals separating out are filtered off. capacity place 30 grammes of the crude thiocarbanilide. the crude product is used . directly. When only about 20 c.c. the mustard 011 separated in a dropping funnel. of the liquid remain in the flask.c. and washed first with water. and distilled. 2 grammes of the dried crude product are recrystallised from alcohol. proceed as above. 15. almost quantitative. 1430. which on recrystallising from alcohol forms colourless crystals. by weight. and finally with water. Yield. C 6 H 5 CS + C 6 H 6 .C 6 H 5 Triphenyl guanidine /1NH. Besides this reaction a second one takes place. N H . and possess a characteristic odour. NH3.aM^f C6H5. NziCnS + C6H5. NH 2 = C = S + H 2 S. like \NH 2 caustic potash and caustic soda.C S . so that the reaction takes place in a shorter time than without the use of the alkali. as hydrochloric acid. and a thiourethane is formed: . sulphuric acid. JNH.C 6 H 5 + H2S\NH.CCH. The reaction takes place in accordance with the following equation: CS h I '= C6H5. N C S + C2H5. O H = C6H5.: /NH. The aromatic mustard oils are in part colourless liquids. If they are warmed for a long time with an alcohol. viz.NH 2 ==Q=N. absorbs carbon dioxide from the air. phosphoric acid. in part crystallisable solids. addition taking place. resulting in the formation of a guanidine derivative: /NH.C6H5 CSS + 2 C6H5. which. In chemical behaviour they are very active. the lower members are easily volatile with steam. From the thioureas thus obtained the mustard oils may be prepared by heating with acids. O # .AROMATIC SERIES 207 Carbon disulphide acts upon primary amines to form symmetrical disubstituted thioureas.g. \ N [ H J C6H5 Phenyl mustard oil The primary amine formed in addition to the mustard oil combines with the acid.CeH^ Diphenyl thiourea = Thiocarbanilide By the addition of caustic potash the elimination of hydrogen sulphide is facilitated. \NH. and it still has the power to form salts. XNH.: the amine formed acts upon some still undecomposed thiourea. the introduction of the three negative phenyl groups in the above compound has not neutralised the basic properties entirely.C6H5 . they combine with the alcohol. e.C6H51 /NH2 Since guanidine C ~ N H is an extremely strong base. Phcnylthiourcthanc ™ * . c. the sulphur is replaced by oxygen. 312. at the same time the extremely disagreeable odour of the phenyl isocyanate arises. from which in the above reverse reaction the mustard oil itself was prepared. 100. . causing tears. with a glass rod. 30 grammes of freshly distilled aniline are added gradually. and an isocyanate is formed. NCO + HgS.NCS + HgO = C6H5. ammonia and primary bases are added with the formation of a thiourea: /NH3 C 6 H 5 . the thiocarbanilide will solidify in crystals. Phenyl isocyanate EXPERIMENT : Heat \ c. By heating with yellow mercuric oxide. ui^fflHfc>ni a test-portion diluted with water and treated 1 A. The yellow oxide is changed to the "black sulphide. NH2 = CS \NH. 120.NCS + C6H5. 60. REACTION: THE STJTLPHONATION OP ATX AMTNE EXAMPLE: Sulphanilic Acid from Aniline and Sulphuric Acid1 To ioo grammes of pure concentrated sulphuric acid in a dry flask. the vapour of the compound attacks the eyes. On stirring the reaction-product after cooling.C e H 5 .C 6 H 5 s-Diphenylthiourea EXPERIMENT : Treat 2 drops of phenyl mustard oil on a watchglass with 2 drops of aniline. until the oil boils.NCS+NH 3 = CS Phenylthiourea /NH. and warm gently over a small flame. 6. of phenyl mustard oil in a test-tube with the same volume of yellow mercuric oxide for some time. 132.163. which may be easily recognised by its extremely disagreeable odour: C6H5. with shakuM^ the mixture is heated in an oil-bath up to 1801900.2O8 SPECIAL PART In the same way. find extensive technical application" in the manufacture of azo dyes. and recrystallised from water. Under the preparation of benzene sulphonic acid. The cooled reaction-mixture is poured.. If the diazo-coimpounds thus obtained are combined with amines or phenols. and in the form of their alkali salts are soluble in water. Sulphanilic acid particularly. The amido-sulphonic acids. Yield. they possess acid properties.g. The aliphatic compounds do not react in a similar manner. a portion of the benzene-hydrogen is replaced by a sulphonic acid group. as in many cases.QH/ dissolve in both acids and alkalies. which \ \CO. in dissolving in alkalies. washed with water. metanilic acid. with stirring. that the sulphonic acid group enters in the para-position to the amido-(NH2) group. /OH /NH 2 C6H5. with the addition of animal charcoal. They differ f /NH* Amidobenzoic acid \ in this from the analogous carbonic acids e. as well as the numerous mono. .and poly-sulphonic acids derived from a and ft naphthyl amines. azo dyes are formed which contain the sulphonic acid group. upon this fact depends their great technical importance. and its isomer. CfiH4< 1. into cold water. i. no aniline separates out: about 4-5 hours' heating will be necessary.AROMATIC SERIES 209 with caustic soda. obtained by the reduction of m-nitrobenzene9ulphonic acid. 30-35 grammes. It is filtered off. When an aromatic compound is treated with sulphuric acid. the details of the reaction will be discussed. since they are derivatives of a primary amine. upon which the sulphanilic acid separates out in crystals. the reaction taking place in accordance with the equation below. may like them be diazotised by the action of nitrous acid. The amido sulphonic acids are colourless crystallisable compounds melting with decomposition. if necessary. it happens. The basic character of the amine is so greatly weakened by the introduction of the negative sulphonic acid group that the amido sulphonic acids cannot form salts with acids.e. \)H \SO3H p-Amidobenzenesulphqntc acid =» sulphanilic acid In the above example. NH2 -f £o 2 = d«H4 + H2O. N = N . under the preparation of methyl amine.c. Further. When all the reducing liquid has been added.7. — free diazoltenzene — possessed the constitution: . in the form of their mineral acid salts. it is obtained perfectly pure. of water. Yield. cool with ice. waiting after each addition until the lively evolution of nitrogen has ceased before adding more. the latter. and treat this solution with a concentrated solution of sodium hydroxide (2 parts to 3 of water). As already mentioned. in a mineral acid solution. until free nitrous acid may be recognised with starch-potassium-iodide paper.c. The diazobenzenechloride solution thus obtained is allowed to flow carefully into a solution of 10 grammes caustic soda in 30 c. Treat the alkaline diazobenzene solution. discovered by Peter Griess. gradually with small portions of the sodium-stannous oxide solution.c. yield diazo-compounds. until the precipitate at first formed (stannous oxide) is redissolved in the excess of the alkali. Cl + 2~H2O Diazobenzene chloride It has been held that the mother substance of the diazo-compounds. well cooled with ice-water. of water contained in a 400 c.c. OH -f N2 + H2O C6H5. NH 2 + NOOH + HC1 = C6H5. 3-4 grammes. and treat with a solution of 5 grammes of sodium nitrite in 15 c. By a careful distillation from a small fractionating flask (without condenser). NH2 + NOOH = CH 3 . flask which is well cooled with ice. the behaviour of the aliphatic primary amines toward nitrous acid is very different from that of the aromatic compounds. dissolve 20 grammes of stannous chloride in 50 c. Boiling-point. the flask is connected with a condenser. and is collected in a test-tube. While the former yield alcohols with the elimination of nitrogen. and the liquid heated to boiling. 8i°. of water. REACTION: REPLACEMENT OP THE AMIDO.c.AND DIAZO-GROUPS BY HYDROGEN EXAMPLE: Benzene from Aniline Dissolve 5 grammes of aniline in a mixture of 15 grammes of concentrated hydrochloric acid and 30 c. of water. CH 3 . The benzene formed passes over first. under the influence of nitrous acid. previously well cooled. N ~ N . Br3 N Diazobenzene perbromide EXPERIMENT : Dissolve 1 c. Br + Br2 = C6H5. Cl) 2 . NO3 = Diazobenzene nitrate. It is. and the one proposed earlier by Blomstrand taken up.AROMATIC SERIES QH5. of aniline in an excess of hydrochloric acid. m in 211 More recently this view has been abandoned.c. N . OH = Diazobenzene sulphate. N 2 .SO2. however. on cooling.c.N=N-OH In accordance with which the diazo salts were expressed by: C6H5. NzzN. C6H5. Cl. A dark oil separates out. of bromine dissolved in a water solution of hydrobromic acid. . Br3 = C6H5. and add 1 c. N—N.OH In accordance with this view the diazotisi ng process consists in replacing the three hydrogen atoms combined with a nitrogen atom having a valence of 5. not accepted generally. SO 2 . by a trivalent nitrogen atom: m H 5 . in which the valence of the nitrogen atom is probably 5. It is washed several times with water. AuCl3 and (C6H5. the diazo salts are called diazonium salts. Nz=N. O. PtCl4 Diazobromides have the power of taking up two atoms of bromine to form perbromides: C6H5. or in a concentrated solution of potassium bromide. N m N .: C6H5. Cl = Diazobenzene chloride. from which the solution is decanted. The diazo-compounds can also form double salts. According to this conception the above salts are represented thus: \C1 \NO3 \O. C6H5. Nz=N. e.g.N( ( NCI Aniline hydrochloride To emphasise the similarity to ammonium compounds. diazotise as above. it solidifies to crystals. does not possess this property at all. N \N 3HBr Diazobenzeneimide EXPERIMENT: The perbromide just obtained is covered with water.N N-ONa Antidiazo compound Does not unite with phenols NaO. The one primarily obtained is characterised by the fact that in alkaline solution it unites with phenols to form azo dyes.N Syndiazo compound Unites with phenols The salts of the diazo-compounds formed with acids are. Bamberger's view is that the diazonium salt first obtained should be represented by V III ONa and that this. and now have the property of combining with phenols to form azo dyes. N 2 . NBr.. at higher temperature if necessary. undergoes a molecular transformation into QHg. insoluble . while the second modification obtained by a longer action of the alkali. Cl + 2 NaOH = C6H5. diazobenzeneimide is obtained: C6H5. NzzN.N = N . If they (the latter) be treated with acids. ONa. In spite of numerous experiments the constitution of these substances is not wholly clear. through the further action of the alkali. or only in a slight degree. they are converted back into the diazonium salts. C6H5. in most cases^ colourless. easily soluble in water.212 SPECIAL PART If ammonia is allowed to act on the perbromide.N C 6 H 5 . Hantzsch. and concentrated ammonium hydroxide added to it. thus acting like acids. ONa + NaCl + H2O These can exist in two isomeric modifications. on the other hand. and explains their differences by stereo-chemical formulae: C6H5. Under the influence of alkalies the diazonium compounds yield salts. crystallisable substances. N. ONa. A vigorous reaction takes place with the formation of an oil possessing a strong odour (diazobenzeneimide). ascribes to both salts the constitution C 6 H 5 . NBr2 + NH 3 = C6H5. On heating. R. ether is added. 2994. generally. the free nitrous acid obtained from sodium nitrite is used. e. — not less than three molecules of hydrochloric acid or two of sulphuric acid to one molecule of a monamine.AROMATIC SERIES 213 in ether.. with explosion. the solid diazo-salts may be prepared by adding to an alcoholic solution of the amine that acid the salt of which is desired. the hydrochloride or sulphate of the amine is difficultly soluble in water. the dry diazo-salts decompose either..g. the very explosive diazobenzenenitrate may be obtained in colourless needles by conducting gaseous nitrous acid into-a well-cooled pasty mass of aniline nitrate and water.H n + HC1 = C6H5. But at present this method is employed only in rare cases. as in the case of diazobenzene nitrate. various methods may be used. In order to diazotise an amine. in working with diazo-compounds. In order to prepare them in the solid condition. Theoretically. a solution of it in a dilute acid — most frequently hydrochloric acid or sulphuric acid — is first prepared. two molecules of a monobasic acid are required to diazotise one molecule of a monamine: C6H-. OH + H2O Amyl nitrite Amyl alcohol If the solid diazo-compound does not separate out at once. Cl + NaCl 4. Under these conditions. NH2 + NO 2 . and treating the diazo-solution with alcohol and ether. For the diazotisation of one molecule of a monamine. In general. In many cases. Cl + C 5 H n . Thus. A few diazo-compounds are so stable that they may be recrystallised from water. In rare cases only. but since the commercial salt is never perfectly pure. it is not necessary to add water until the salt is entirely dissolved. and then treating the well-cooled mixture with amyl nitrite: 1 C6H5. it is advisable to weigh off from 5-10 % more than the calculated amount. theoretically. NH2 + NaNO2 + 2 HC1 = C6H. NzzN. . is it necessary to isolate them in a pure condition. These compounds were formerly obtained by passing gaseous nitrous acid into a salt of the amine until it was diazotised. it passes into solution. the very easily prepared water solutions are used. one molecule of sodium nitrite is necessary.2 H2O but an excess is always taken. C. but the solution of the nitrite may be poured into the pasty mass of crystals .. when the undissolved salt is diazotised. and to determine by the method given below when a sufficient quantity •• I B . or a sudden evolution of gas takes place without detonation. 23. larger quantities may be added at one time. With this mixture. After drying. it happens that the . the addition of the nitrite is not discontinued at once. no dark spots appear. and the liquid must not be allowed to become warm. and so on. the mixture shows the presence of nitrous acid. but toward the end of the reaction small quantities must again be employed. in that he cools the amine solution with a freezing mixture.214 SPECIAL PART of this has been added. the strips are dried by suspending them from a string in a place free from acids. generally 5-10 parts of water to 1 part of salt. and further portions of the sodium nitrite may be added. But if a dark spot is formed at once. prepared as follows. the cooled solution is first treated with a small portion of the nitrite solution. and a drop of it transferred with a clean glass rod to the starchpotassium-iodide paper. is used: A piece of starch the size of a pea is finely pulverised. In many cases. after standing some time. or the amine solution is cooled by ice. it is well stirred. as well as to be able to determine when it is completed. one waits until the reaction has been completed. in a little water. wide. and adds the nitrite solution drop by drop from a separating funnel. starch-potassium-iodide paper. and is then tested again. the temperature of the solution must be lowered and the nitrite added more slowly. At times. The nitrite solution must be added gradually to the amine solution. In order to be cognisant of the course of the reaction. the strips are cut up and preserved in a closed vessel. the test is again repeated. After the addition of three-fourths of the nitrite solution. the nitrous acid is still present. saturate long strips of filter-paper 3 cm. and so on. it is boiled a short time. of boiling water. The diazotisation is ended when. Since the diazotisation of the last portions of the amine often requires some time. a solution of a crystal of potassium iodide the size of a lentil. or ice is thrown into the water. before more of the nitrite is added. It is very convenient to cool the solution. After cooling. is added to it. and added to 200 c. but by throwing into it from time to time small pieces of ice. the experimenter is often too careful.c. and in this case. even if after one minute the test for nitrous acid is obtained. not from without. If the nitrous acid is already used up in the diazotisation. The nitrite is dissolved in water. In order now to diazotise an amine. The nitrite solution may be poured directly from a flask. If the addition causes evolution of gas bubbles or vapours of nitrous acid. but the solution is allowed to stand 5-10 minutes. Frequently it is sufficient to place the solution in a water-bath filled with cold water. with stirring. the test wil> not show the presence of nitrous acid.AROMATIC SERIES 215 weighed-ofF quantity of sodium nitrite is apparently not sufficient to complete the diazotisat. may be treated with sodium nitrite. acidified with sulphuric acid. in case the weighed-ofF amount of sodium nitrite is not sufficient. or a precipitate separates out.g. and consequently the nitrite cannot enter into tht. 22. as in the above case. The replacement of a diazo-group by hydrogen may be effected by other reducing agents. reaction. if. paraleucarnline with i B. thus liberating two hydrogen atoms. the constitution of which was unknown for a long time. Further. a diazo-compound is boiled with alcohol. or by heating the amine with alcohol saturated with ethyl nitrite. The replacement of the diazo-group by hydrogen in the above reaction takes place in accordance with the following equation: C C H 5 . . Thus. or the boiling alcohol solution of the amine. and where it is of importance to prepare the amido-free compound (see below). If. such a reaction is superfluous. But there are cases in which an amine is not obtained in this way.0H + CH 3 . At this place. They heated the diazo-compound of the leuco-base of the dye. This was first explained by E. and this is then tested to determine whether the desired reaction has taken place. This phenomenon has its . e. Fischer.N o .OH + H2 = C6H6 + N s + HaOl In this way it is possible in many cases to replace a primary amidogroup by hydrogen. This is the diazoamido-compound.CH 2 .N 2 . and that even after the addition of a fresh quantity. On the addition of acid and solution of the nitrite. Obviously. two examples may be mentioned which illustrate the theoretical as well as the practical value of the reaction: by the oxidation of a mixture of aniline and p-toluidine. the amine is obtained by the nitration of the hydrocarbon and the reduction of the nitro-compound. the latter is converted into aldehyde. often the diazo-solution becomes cloudy toward the end of the reaction.OH = C6H6 + N2 + CH 8 . some acid is first added to a small portion of the liquid..ause generally in the fact that the acid (hydrochloric or sulphuricN has been used up.on. by which the diazo-compound is reduced: C c H 5 .CHO + H2O Aldehyde The reaction is effected either by conducting gaseous nitrous acid into the boiling alcohol solution of the amine. and O. para-fuchsine. its formation is also caused by the lack of free acid. the precipitate disappears. 587. there is formed a complex dye. OH = X. this results in the formation of the o. until it shows a blue spot on starch-potassium-iodide paper. using the method last described.and p-compounds only. as the nitro-amines. with stirring. SO4H + C2H5. If the amido-group is replaced by hydrogen. halogen-substituted amines. it is treated with a solution of 8. with stirring. 194. but all the derivatives of these. The diazobenzene sulphate sola- .c. the starting-point is p-toluidine. NizN. 8. by allowing it to flow down the side of the beaker. amido-carbonic acids. REACTION: REPLACEMENT OF THE DIAZO-GROUP BY HYDROXYL EXAMPLE : Phenol from Aniline Pour 20 grammes of concentrated sulphuric acid as rapidly as possible. the desired m-nitrotoluene is obtained. In order to obtain the m-nitrotoluene. After the hot liquid has been cooled by immersion in cold water. amido-aldehydes. This is nitrated. X . of water. upon which a nitrotoluidine of the following constitution is obtained: NH. the following case is cited: No method. 270).2l6 SPECIAL PART alcohol.is known by which m-nitrotoluem can be prepared by the nitration of toluene. thus giving rise to a phenol ether. then add 100 c. to the hot solution add 10 grammes of freshly distilled aniline.5 grammes of sodium nitrite in 40 c. By boiling a diazo-compound with alcohol the reaction may take place in a different way. As an example of the preparation value of th : reaction. but by the ethoxy (-OC2H5) group. special attention is called to the fact that not only aniline and its homologues can be diazotised. OC2H5 + N2 + H2SO4 In conclusion. into 50 grammes of water. of water. at times the diazo-group is not replaced by hydrogen. which gave the mother substance — the hydrocarbon triphenyl methane (A. etc.c. and the residue of phenol is subjected to distillation in a small flask. Under certain circumstances. e. and the distillate. it will pass over to a phenol with the evolution of nitrogen. The ether is then evaporated. a small quantity of oxydiphenyl crystallises out.C 6 H 4 .g.AROMATIC SERIES 217 tion thus obtained is gently heated (40-50°) for half an hoar on the water-bath. and Diphenyliodonium iodide?) A solution of ro grammes of aniline in a mixture of 50 grammes of concentrated hydrochloric acid and 150 grammes of water . like amido-carbonic acids. etc. halogen substituted amines. but to add a water solution of the calculated amount of sodium nitrite to a boiling solution of the amine in dilute sulphuric acid. Yield. Phenyl iodite. the phenol is then distilled over with steam. since.) 9. O. The diazotisation of the substance and the immediate decomposition of the diazocompound take place in one operation. The liquid remaining back in the flask after the steam distillation is filtered hot. : C6H5.OH 4. SO 2 . C6H4. On cooling. OH + N2 + H2SO4 For this reaction the diazosulphate is most advantageously used. OH + HOH = C6H5. The oxydiphenyl obtained as a by-product is formed in consequence of the action of some of the undecomposed diazo-compound on phenol: CGH5. after being saturated with salt. REACTION: REPLACEMENT OF A DIAZO-GROUP BY IODINE EXAMPLE : Phenyl Iodide from Aniline {PhenyliodideMoride. 3705. The ethereal solution is allowed to stand for some time over fused sodium sulphate.SO4H + H. is extracted several times with ether. 183°. If a diazo-compound is heated with water. it is more convenient not to isolate the diazo-compound. The same reactions are also applicable to substituted amines. Nz:N. But the use of the diazonitrate is avoided. acting upon the phenol. the diazochloride may also be employed.N2.OH = C 6 H 5 .H2SO4 + N 8 (Compare B. readily forms nitro-compounds. Iodoso-benzene. the nitric acid liberated. 7-8 grammes. 23. In many cases. amido-sulphonic acids. in this case. Boiling-point. 2i8 SPECIAL PART cooled with ice-water is gradually treated with a solution of 8.5 grammes of sodium nitrite in 40 c.c. of water, until a test will give a blue colour to the starch-potassium-iodide paper. The diazosolution is then treated in a flask, not too small, with a solution of 25 grammes of potassium iodide in 50 c.c. of water, the mixture is allowed to stand several hours, being cooled by water, finally it is gently heated on the water-bath until the evolution of nitrogen ceases. The liquid is made strongly alkaline with caustic soda or caustic potash, and the iodobenzene distilled over with steam ; the steam delivery tube should reach almost to the bottom of the flask. The iodobenzene is separated from the water in a dropping funnel, dried with calcium chloride and redistilled. Boilingpoint, 189-1900. Yield^ about 20 grammes. If a diazoiodide is heated, the diazo-group is replaced by iodine, the reaction taking place smoothly in most cases. The reaction is effected by diazotising the amine in a hydrochloric acid or sulphuric acid solution, and then treating it with potassium iodide. From the diazochloride or diazosulphate there is formed a diazoiodide, the reaction, in many cases, taking place at the ordinary temperature; in others, on heating, as above. Since the reaction occurs without difficulty, it is used as the method of preparation of many iodides. The aromatic iodides possess the noteworthy property of combining with two atoms of chlorine, the iodine previously univalent becoming trivalent: Phenyliodidechloride EXPERIMENT: The phenyl iodide obtained is dissolved in five times its volume of chloroform, the solution is cooled by ice-water, and a current of dry chlorine is passed into it from a very wide delivery tube, until no more is absorbed. The crystals separating out are filtered off, washed with a fresh quantity of chloroform, spread out in a thin layer on a pad of filter-paper, and allowed to dry in the air. M-pr-33.154- B.25,3494; 26,357; 25,2632. AROMATIC SERIES 219 If caustic soda is allowed to act on an iodochloride, the two chlorine atoms are replaced by one oxygen atom, and an iodoso-compound is obtained: C 6 H 5 . IC12 + H2O = C 6 H,. I—0 + 2 HC1 Iodosobenzene Besides this reaction another takes place, resulting in the formation of an iodonium base. This formation is probably due to the fact that a small part of the iodosobenzene is oxidised to phenyl iodite, and this condenses with iodosobenzene, .iodic acid being eliminated: /OH C6H5. I < + IO 2 . CeH5 = C6H5 - I - CGH5 + HIO3. \OH I Hypoth. Iodosobenzene hydrate OH Diphenyliodonium hydroxide This base is present in the alkaline solution filtered off from the iodosobenzene. If the filtrate be treated with sulphur dioxide, this reduces the iodic acid to hydriodic acid, which, combining with the iodonium base, forms an iodide insoluble in cold water: HIO3 + 3 SO2 = HI + 3 SO3 = C 6 H 5 - I - C 6 H 5 + H2O [OH+HII 1 m I The iodochloride is carefully triturated with dilute caustic soda in a mortar (for 1 gramme of the iodochloride, use a solution of 0.5 gramme sodium hydroxide in 4 grammes of water), and allowed to stand over night. The iodosobenzene is then filtered off, washed with water, and pressed out on a porous plate. The alkaline filtrate is treated with a solution of sulphur dioxide until it smells strongly of it. The precipitate formed is filtered off and dissolved in hot water. On cooling, colourless needles of diphenyliodonium iodide are obtained. EXPERIMENT : The iodoso-compounds have the power of uniting with acids to form /OH salts, in which they act like a di-acid base, e.g., C0H«.I\ \OH EXPERIMENT : Several grammes of iodosobenzene are dissolved with heat in as small a quantity of glacial acetic acid as possible; 22O SPECIAL PART the solution is evaporated on the water-bath to dryness, in a watchglass, or shallow dish. The solid residue is pulverised and recrystallised from a little benzene. Iodosobenzene acetate is thus obtained, /OOC.CH^ C 6 H 5 .I<; X)OC.CH3 in the form of colourless prisms, melting at 15 f. The iodoso-compounds, on treatment with hydriodic acid, are reduced to iodides, with a separation of iodine. C6H5. IO + 2 HI = C6HS.I + l2 + H2O This reaction is used for the quantitative determination of iodosooxygen. EXPERIMENT: Some potassium iodide is dissolved in water, acidified with dilute sulphuric acid, or acetic acid, and a few grains of iodosobenzene are added. The iodine separates out as a brown precipitate. If an iodoso-compound is heated carefully to ioo°,-it passes over to an iodite (Jodoverbindimg) : 2C6H5.IO = C6H,.IO2+ C6HrI Phenyl iodite Phenyl iodide The same compound may also be obtained by treating an iodosocompound with steam. EXPERIMENT : Iodosobenzene is treated in a flask with enough water to form a thin paste. Into this steam is conducted (apparatus for distillation with steam), until no more phenyl iodide passes over with the steam and all the iodosobenzene has been dissolved. If the phenyliodite formed does not dissolve completely, water is added until solution takes place. The solution is then evaporated on the water-bath until a test-portion cooled off yields an abundant crystallisation of phenyl iodite. The iodites, like the iodoso-cornpounds, puff up and suddenly decompose on heating. (Try it.) They also abstract iodine from hydriodic acid, and in double the quantity as compared to the similar action of the iodoso-compounds. AROMATIC SERIES CGH6. IO2 + 4 HI = C6H5I + 4 I + 2 H2O 221 They do not form salts with acids. The iodonium bases are prepared most conveniently by the action of silver oxide on a mixture of equal molecules of iodoso and iodite compounds: CCH5.10 + C 6 H 5 . 10, + AgOH = C 0 H 5 .?. CflH, + AgIO3 OH They are soluble in water, show a strong alkaline reaction like the sulphonium and ammonium compounds, and give with halogen hydracids precipitates of the corresponding salts. If the dried salts be heated, they decompose into two molecules of the hydrocarbon substitution product, e.g.: ? I EXPERIMENT : The diphenyliodonium iodide obtained as a byproduct in the preparation of iodosobenzene is heated carefully in a test-tube over a small flame. Suddenly the substance begins to melt in one place; the fusion increases, without the need of further heating, and the whole mass boils up. Iodobenzene, easily recognised by its odour, is obtained. 10. REACTION: REPLACEMENT OP A DIAZO-GROUP BY CHLORINE, BROMINE, OR CYANOGEN EXAMPLE : p-Tolyl Nitrile from p-Toluidine Dissolve 50 grammes of copper sulphate in 200 grammes of water in a 2-litre flask by heating on the water-bath; then add gradually, with continuous heating, a solution of 55 grammes of potassium cyanide in 100 c.c. of water. Since cyanogen is evolved, the reaction must be conducted under a hood, with a good draught, and the greatest care taken not to breathe the vapours. While the cuprous cyanide solution is further gently heated up to about 60-70° on the water-bath, the diazotoluenechloride solu- 222 SPECIAL PART . tion is prepared in the following way: 20 grammes of p-toluidine are heated with a mixture of 50 grammes of concentrated hydrochloric acid and 150 c.c. of water until solution takes place; the liquid is then quickly immersed in cold water and vigorously stirred with a glass rod, in order that the toluidine hydrochloride may separate out in as small crystals as possible. A solution of 16 grammes of sodium nitrite in 80 c.c. of water is then added to the amine hydrochloride, cooled by ice-water, until a permanent reaction of nitrous acid upon the starch-potassium-iodide paper is obtained. The diazotoluene chloride thus formed is poured from a flask into the cuprous cyanide solution, with frequent shaking. After the addition of the' diazo-solution, which should require about 10 minutes, the reaction mixture is heated on the water-bath for about a quarter-hour. The tolyl nitrile is then distilled over with the steam. This operation must also be done under a hood with a good draught, since hydrocyanic acid passes over. The nitrile distils as a yellow oil, which after some time solidifies in the receiver. It is separated by decanting the water, pressed upon a porous plate, and purified by distillation. If the oil will not solidify, the entire distillate may be taken up with ether, the ethereal solution shaken with caustic soda solution to remove the cresol, and then, after evaporating the ether, the residue remaining is distilled directly, or, in case it is solid, it is pressed out on a porous plate, as above, and then distilled. Boilingpoint, 218°. Yield, about 15 grammes. The diazo-group cannot be replaced in the same way by iodine as by chlorine, bromine, or cyanogen. If a water solution of a diazochloride, -bromide, or -cyanide is heated, a phenol is formed, as is also the case on heating a diazo-sulphate: C6H5.N2.C1 + H2O = C6H5. OH + N2 + HC1 To Sandmeyer1 we are indebted for the important discovery that, if the heating be done in the presence of cuprous chloride, bromide, or cyanide, the reaction taking place is analogous to the one by which phenyl iodide is formed: 1 B. 17,1633 and 2650; 18,1492 and 1496. AROMATIC SERIES 223 r rv X r™ rxx ™ T XT I corresponding cuprous salt T C B H 5 .N 2 .CN = C 0 H 5 .CN + N2 J V N ttr - P H Br I N I In the Presence of t h e The manner in which the cuprous salts act is not known; in any case they unite first with a diazo-compound to form a double salt, which plays a part in the reaction. The reaction in the above preparation of cuprous cyanide takes place in accordance with the following equation: CuSO4 + 2 KCN = CuCN2 + K2SO4 2 CuCN2 = Cu2CN2 + 2 CN In order to replace the diazo-group by chlorine or bromine, the above method is followed exactly. A diazo-solution is first prepared, and gradually added to a heated solution of cuprous chloride or bromide. With easily volatile chlorine or bromine compounds, it is desirable to use a reflux condenser, and to allow the diazo-solution to flow in from a dropping funnel. In some cases it is more advantageous not to use a previously prepared diazo-solution, but to proceed as follows: The amine is dissolved in an acid solution of a copper salt; this is heated, and to the hot solution, the solution of nitrite is added from-a dropping funnel. The diazotisation and replacement of the diazo-group then takes place in one reaction. If the reaction-product is not volatile with steam, it may be obtained from the reaction-mixture by filtering, or extracting with ether. The Sandmeyer reaction is capable of general application. Since the yield of the product is generally very good, for many substances it is used as a method of preparation. It should be finally pointed out that by the replacement of the diazo-group by cyanogen a new carbon union takes place. 1 1 . REACTION: (a) REDUCTION OP A DIAZO-COMPOUND TO A HYDRAZINE. (i) REPLACEMENT OF THE HYDRAZINE-RADICAL BY HYDROGEN EXAMPLES : (a) Phenyl Hydrazine from Aniline (£) Benzene from Phenyl Hydrazine (a) Add IO grammes of freshly distilled aniline to IOO c.c. of concentrated hydrochloric acid in a beaker, with stirring; aniline hydrochloride partially separates out in crystals. To the mixture, SPECIAL PART cooled with ice, add slowly from a dropping funnel, a solution of 10 grammes of sodium nitrite in 50 c.c. of water, until a test with starch-potassium-iodide paper shows free nitrous acid. In this case the strong acid solution must not be brought directly upon the test-paper, but a test-portion is diluted with water in a watchglass and then the test applied. To the diazo-solution add, with stirring, a solution of 60 grammes of stannous chloride in 50 c.c. of concentrated hydrochloric acid cooled with ice ; a thick paste of crystals of phenyl hydrazine hydrochloride separates out. After standing several hours this is filtered off with suction (Biichner funnel and filter-cloth), the prepipitate is pressed firmly together on the filter with a pestle; it is then transferred to a small flask and treated with an excess of caustic soda solution. Free phenyl hydrazine separates out as an oil, it is taken up with ether, the ethereal solution dried with ignited potash, and the ether evaporated. For the later experiments the phenyl hydrazine thus obtained can be used directly. If it is desired to purify the substance, the* best method is to distil it in a vacuum, or it can be cooled by a freezing-mixture, and the portions remaining liquid are poured off. Yield, about 10 grammes. Since the diazotisation in a strong hydrochloric acid solution as well as the filtration of strongly acid liquids is liable to miscarry, it is better to perform the experiment as follows: Dissolve 10 grammes of freshly distilled aniline in a mixture of 30 grammes of concentrated hydrochloric acid and 75 c.c. of water and diazotise it with a solution of 8 grammes of sodium nitrite in 30 c.c. of water, the beaker being cooled with ice-water. The diazosolution is saturated with finely pulverised salt (about 30 grammes) with shaking; the solution is poured off from any undissolved salt, and being cooled with ice is treated with a cold solution of 60 grammes of stannous chloride in 25 grammes of concentrated hydrochloric acid. After several hours' standing, the phenylhydrazine hydrochloride separates out, this is filtered off with suction, washed with a little saturated salt solution, pressed out on a porous plate, and treated as above. (£) In a i-litre flask provided with a dropping funnel and con- 1 by reducing the diazo-compounds with stannous chloride and hydrochloric acid: C0Ha. the benzene is immediately distilled over with steam and collected in a test-tube.Cl + 2 H2 = C({Ht. boiling at 8i°. By another careful rectification from a small fractionating flask (without con- FIG. 16. Monosubstituted hydrazines of the type of phenyl hydrazine may be obtained according to the method of V.NH.Na. about 5 grammes. Since the hydrochlorides of the hydrazines are difficultly soluble in concentrated hydrochloric acid. 2976. Meyer and Lecco. is obtained. 6S) 150 grammes of water and 50 grammes of copper sulphate are heated to boiling. Yield.. Q . 68.NH2r HC1 Pfienyl hydrazine hydrochloride The reaction is always conducted as above : The amine is diazotised in a strong hydrochloric acid solution. pure benzene. then from the funnel add gradually a solution of 10 grammes of free phenyl hydrazine in a mixture of 8 grammes of glacial acetic acid and 75 grammes of water. The oxidation of the phenyl hydrazine proceeds with an energetic evolution of nitrogen. and then a solution of stannous chloride in strong hydrochloric acid is added to it.AROMATIC SERIES denser (Fig. these separate out directly on the addition of the 1 B. denser). C4H4 + C8His. on evaporation. N H . If neutral sodium sulphite is allowed to act on a diazo-salt. The monosubstituted hydrazines possess a basic character.: QH-.: C 6 H. N 2 . which is slower. which. C f t + H2O. .2976.. or with zinc dust and acetic acid. Na = C 6 H.67.NH 2 BenzaWehyde = C6H5. and are eliminated as water: 2 C 6 H 5 . and phenyl hydrazine hydrochloride is formed. they combine with only one molecule of a monobasic acid. and also by another method. but cheaper than the former. CjHr/ Bcnzophcnoatf * A . 23. and can easily be obtained pure by filtration. in spite of the fact that they contain two ammonia residues. it takes up two atoms of hydrogen and is converted into a hydrazine sulphonate : CeH5 . N H . as above.g.Hi. SO3Na Sodium phenyl hydrazine sulphonate 1f this is heated with hydrochloric acid. Phenyl hydrazine hydrochloride Phenyl hydrazine reacts with aldehydes and ketones. e. No. the acid radical of the diazo-compound is replaced by a residue of sulphurous acid. The reduction of the # diazo-compounds to hydrazines may be accomplished by the method of Emil Fischer 1 which led to the discovery of this class of compounds.NH2=: * \ c = N .226 SPECIAL PART stannous chloride.NH. CH=zN.or CO-groups.HC1. Cl + NaSO.NH.g. e. the two hydrogen atoms of the amido-groups unite with the oxygen atom of the CHO.NH.16. crystallises out: According to this method.CO. SO3Na + H 3 = C6H5. N H . SO3Na + NaCl Sodium diazobenzenesulphonate If this srJt is now reduced with sulphurous acid. phenyl hydrazine is prepared on the large scale.NH 2 ..<. 190. N>. the sulphonic acid group is split off. CeH5 + H2O Benzylidenephenyl hydrazone . NH. OH. If this is added to an aldehyde orketone. the fundamental explanations of the last few years in this field could scarcely have been made. EXPERIMENT : To a mixture of 4 drops of phenyl hydrazine and 5 e x . Since.(CH. OH) 4 .NH 2 Grape sugar = CH 2 ." In the above example. perfectly pure free phenyl hydrazine may be purchased in the market.CHO + C 6 H 5 . In order to prepare a hydrazone. diluted with three times its volume of water. which again reacts with the hydrazine. the hydrazone. but in others only on heating. at present.OH) 4 .OH) groups adjoining the aldehyde (CHO) group is oxidised to a ketone group. there is obtained a compound of this composition: CH 2 . At first there appears a milky turbidity. e. The compound thus obtained is called an "Osazone. add 3 drops of glacial acetic acid. is used as the reagent. it acts as an oxidising agent toward the sugar. Phenyl hydrazine is of extreme importance in the chemistry of the sugars for the separation.g. a mixture of equal volumes of phenyl hydrazine and 50 % acetic acid. To this is added 2 drops of benzaldehyde (from a glass rod).. there is formed. in many cases at the ordinary temperature.: CH 2 . Without this reagent. The smallest quantity of benzaldehyde may be recognised in this way.NH. formerly a solution of I part of phenyl hydrazine hydrochloride and i j parts of crystallised sodium acetate in 10 parts of water was used as a reagent. and transformation of the different varieties of the sugars. a normal hydrazone is formed. recognition. e.C—CHz=N. extracting water.AROMATIC SERIES 227 This reaction can be used for the recognition and detection of aldehydes and ketones. If one molecule of phenyl hydrazine is allowed to act on one molecule of a sugar. CH + H2O But if the phenyl hydrazine is used in excess. OH (CH.C 6 H 5 N NH. of water. and the mixture shaken.C 6 H 5 . one of the secondary alcohol (CH.OH) 3 . in the above case. but very soon a flocculent precipitate of benzylidenephenyl hydrazone separates out.g.NH.OH(CH. the grape sugar into fruit sugar. the osone is: CH2. by the action of methyl iodide. If this compound is treated with a reducing agent. but an oxidation product of it is obtained.C 3—N N—C6H5 Antipyrine .CO. of water is treated with a solution of 1 gramme of pure grape sugar in 5 c. After heating an hour.OH(CH.OH. the crystals are filtered off. yellow needles of the osazone begin to separate out. the important febrifuge — u Antipyrine " — dimethyl phenyl pyrazolone is obtained: CHj. and the original sugar is not obtained: CH.c. Phenyl hydrazine undergoes condensation with /3-diketones and )S-ketone-acid-esters with th'e formation of ring compounds contain-' ing nitrogen — the so-called pyrazoles and pyrazolones. 205 °. and warmed on the water-bath.C O I. (CH.c. CHO. and allowed to dry in the air. the fine.." In the example selected. After about 10 minutes. The phenyl methyl pyrazolone formed from acetacetic ester and phenyl hydrazine is of importance: CH*.OH)3. and phenyl hydrazine is eliminated. OH)3. the aldehyde group and not the ketone group is reduced. OH. of water. EXPERIMENT : A cold solution of 2 grammes of phenyl hydrazine hydrochloride and 3 grammes of crystallised sodium acetate in 15 c. Melting-point. washed with water. it acts in the same way as all hydrazones.CH^COfoCsH^] = CH 3 ~ C-CH 2 .CnCH—CO Hj.CH2. a sorcalled " Osone. The aldose is converted into a ketose. the original unchanged sugar is not formed again. The general importance of the reaction as applied to the sugars may be inferred from these brief statements.228 SPECIAL PART If this compound is heated with hydrochloric acid. CO.CO + H2O + C2H5OH HJN ^ N NC G H 5 from which. the quantity is increased by a longer heating. and treat with a solution of 4. NH 2 + CuO = C6H6 + N2 + H2O + Cu. the oxidation may be effected in an open vessel. CGH5. If it is desired to prepare an amido-compound from an amido-free compound. then. Cl + N 3 + 2 H2O. in a solution of 3. as above. To this mixture.5 grammes of an1 a 18. d b i h l f The statements made above concerning the replacement of a diazogroup by hydrogen are also applicable to this reaction. or Q H 5 . If a hydrochloric acid salt of a hydrazine is oxidised. is added a quantity of hydrochloric acid solution corresponding to 2. NH 2 + 2 CuO = C6H6 -f N2 + H2O + Cu2O. benzene: d.c. NH 2 . as in the example cited. and there is obtained. N H . HC14.' it may happen that the hydrazine radical will be replaced by chlorine: C6H5. In a case of this kind. REACTION: (a) PREPARATION OP AN AZO DYE PROM A DIAZOCOMPOUND A N D AN AMINE. the hydrochloric acid salt of the corresponding hydrazine is prepared. 2 B.1 or ferric chloride.) from phenyl hydrazine. and oxidised with caustic soda. e.c. of water. of water. 1 2 . dried on the water-bath.2 grammes of pure sodium nitrite in 20 c. . the free hydrazine is liberated.O2 = C6H5. i8. (*) REDUCTION OP THE AZO-COMPOUND EXAMPLES : (a) HeliantMne from Diazotised Sulphanilic Acid and Dimethyl Aniline (£>) Reduction of Helianthine (a) Dissolve 10 grammes of sulphanilic acid. which may give rise to complications. after being cooled by water. N H . the reaction product is obtained either by filtering or by extracting with ether.5 grammes of dehydrated sodium carbonate in 150 c.90.2 the hydrazine radical is replaced by hydrogen.g. and subject this to oxidation. N H . The amido-free substance is not always easily volatile. and if the direct reduction of the diazo-compound by sodium stannous oxide or alcohol (see page 210) has been shown to be impracticable.786. It may be pointed out here that it is more convenient to separate the hydrazine from the hydrochloric acid salt.AROMATIC SERIES 229 If the primary hydrazines are boiled with copper sulphate. The hydrochloric acid salts of bases. of water. p.230 SPECIAL PART hydrous hydrochloric acid. gr. In consequence of the weak basic character of the amines. Vol. II. For this purpose. on the contrary. 31S.)1 Before diazotising the sulphanilic acid. it is treateti with 25 c.^ sp. The dimethyl aniline hydrochloride thus obtained is added to the diazo-solution.g. caustic soda. 2X134 = 268. concentrated hydrochloric acid is diluted with an equal volume of water.$. 1 If the specific gravity of the hydrochloric acid has been determined. and ammonium hydroxide. the percentage of free anhydrous acid may be found without a table. by* the following calculation: The decimal number is multiplied by 2. their hydrochlorides still give an acid reaction with blue litmus-paper. Jf the sp. Percentage contents = 2$. small quantities of concentrated hydrochloric acid are added. and the mixture is made distinctly alkaline by the addition of not too much caustic soda solution. after each addition a test is made to show.c. the dye is recrystallised from a little water. and. to find the amount of anhydrous hydrochloric acid corresponding to the reading of the hydrometer. with stirring. the quantity can be increased if 25 grammes of finely pulverised sodium chloride are added to the solution. and the specific gravity of the dilute acid is determined by a hydrometer. a table must be ld . gr. and a decimal point placed after the first two figures thus obtained. e. After filtering off and pressing out on a porous plate. Red fuchsine-paper possesses the property of becoming decolourised by fre*e hydrochloric acid. therefore an acid reaction can be jobtained even at the beginning of the neutralisation. The dye separates out directly. whether or not the fuchsine-paper is decolourised. Consult a table. (See Graham-Otto.18. by gradually treating with the acid and testing with blue litmus-paper until the liquid is just acid. which converts the red monoacid fuchsine into a colourless polyacid salt. Aromatic bases cannot be neutralised with hydrochloric acid in the same way as caustic potash.134. a solution of 7 grammes of dimethyl aniline in the theoretical amount of hydrochloric acid is prepared. = 1. is greater than 1. In order to neutralise the dimethyl aniline (7 grammes). do not produce this decolourisation. of water. to form the Azo dyes:2 B. If the colour is too intense. 3. and the solution filtered. To this mixture now add several drops of a dilute solution of ferric chloride. The paper must not be an intense red. dissolved by heating in 100 c. the size of a lentil. the red colour of which is changed to blue by free acid. B. wide.AROMATIC SERIES 23 I Preparation of Fuchsine-Paper: A crystal of fuchsine. the ethereal solution dried with potash. 2235. It is then extracted with ether several times. Diazo-compounds react with amines. is pulverised. the commercial Congo-paper will serve. as well as phenols. The filtrate is diluted with water. The colourless solution is then well cooled. . Instead of the fuchsine-paper. Into this immerse strips of filter-paper 2 cm. but only a faint rose colour. sulphanilic acid separates out: it is filtered off through asbestos or glass-wool. Reactions of p-Amido dimethyl Aniline:* The amidodimethyl aniline is treated gradually with small quantities of dilute sulphuric acid until it is just dissolved. Add a few drops of this solution to a dilute solution of hydrogen sulphide in a beaker which has been treated with J-$ of its volume of concentrated hydrochloric acid. they are dried either by suspending from a string in an acid-free place. 233. treat with a solution of 8 grammes of stannous chloride in 20 grammes of hydrochloric acid until decolourisation takes place. especially if the sides of the vessel are rubbed with a glass rod. 60. 137. and caustic soda solution is added until the oxyhydrate of tin separating out at first is again dissolved. while the solution is still hot. (p) Dissolve 2 grammes of the dye in the least possible amount of water by heating. An intensely blue colouration. due to the formation of methylene blue. the fuchsine solution must be correspondingly diluted with water. 2 A . or on the water-bath. and the ether evaporated. upon which. 16. upon which the p-amidodimethyl aniline remains as an oil: on cooling and rubbing with a glass rod.c. takes place. it solidifies. aTHJ. the diazo-compounds of the just mentioned bases can be employed as the starting-point.Aniline iphenylami = Chrysoidine.g. like diphenyl amine.N=N. p-toluidine. Nz:N.N(CH 3 ) 3 = C6HS. and the resulting residues unite. cuminidine. Diazotised sulphanilic acid + dimethyl aniline m-C H H / C6 / /SO3 H /SO 3H \NzzN .OH + HCl This reaction is not so easily explained by the new diazonium formulas. naphthols. like o-toluidine. the generation of the azo-compounds may be readily formulated by assuming that the acid radical of the diazo-compound combines with a benzene hydrogen atom to form an acid. In addition.: C6H5. the large number of a. especially their sulphonic acids.and /3-naphthyl amines mono.to poly-sulphonic acids. especially the numerous sulphonic acids of both naphthols. a-naphthyl amine.C1 + C 6 H 5 . in the preparation of the azo dyes. etc.C 6 H 4 . the vast number of monoazo dyes are prepared.. Since a dye must be soluble in water. other bases. Diazot.N 2 .OH + HC1 (In presence of alkali) Oxyazo benzene In accordance with the earlier views concerning the structure of the diazo-compounds.C 6 H 4 . e. and in part also with secondary and primary amines.OH = C 6 H 5 . metanilic acid.C 6 H 4 . xylidine. the most varied derivatives of these bases. In accordance with these two typical reactions.2 $2 SPECIAL PART (1) C 6 H 5 . the starting-point is usually a sulphonic acid. and the alkali salts of the sulphonic acids of the dyes are more easily soluble than the mother substance containing no sulphonic acid groups. C | H j / Diazot. the diazocompound can be combined or " coupled " with other tertiary. Amidoazo Dyes SO3H . C6H4.N-N.C1 + C 6 H 5 . Instead of dimethyl aniline. instead of diazotised aniline. /2-naphthyl amine. C6H5 = Metanilic Yellow. etc.N(CH 3 ) 3 = Helianthine. or m-diamines. or the sulphonic acids of these phenols. NizN. like sulphanilic acid.C 6 H 4 . may be used. In the second reaction. and these can be combined with mon-acid phenols. NzZxV. Metanilic add + diphenylamine C6H5. A few examples will explain these statements: I. j d i i . The great number of possible combinations can be inferred from the following considerations: In reaction (i). therefore. C6H4.N 2 . or diacid phenols like resorcinol. NH. N(CH 3 ) 2 + HC1 Dimethylamidoazo benzene (2) C 6 H 5 .OH = C G H 5 . like cresol. may also be employed. By energetic reduction. NzzN. C 6 H 3 . the hydrogen atom in the para position to the amido. then the constitution of the azo dyes is also determined. the double NzzN union is broken up.: From this equation it is evident that by reduction. the amine which was diazotised — in the above case sulphanilic acid — may be obtained again on the one hand. The question may be answered by investigating the reduction products of the azo dyes. Oxyazo Dyes /SO3H p-C6H/ . Xylidine + 0-naphthol disulphonic acid Concerning the constitution of the azo dyes. If the para position is already occupied. the o-hydrogen atom unites with the acid radical. C10H6. best in acid solution with stannous chloride. e. when a diazo-compound combines with an amine or phenol. OH = Orange II. It may be stated as a general rule that. Sulphanilic acid + /3-naphthol c 233 Diazot. two molecules of a primary amine. the only question to solve is: which hydrogen atom of the undiazotised component combines with the acid radical of the diazo-compound (the acid thus formed being eliminated).or hydroxyl-group is always substituted. If the constitution of this second product can be determined.g. a-Naphthionic acid + j3-naphthol ioHe\ • c io H 6 • 0 H = \NzzN Fast Red (firs* r e d azo dye). provided the components are known..N=N.AROMATIC SERISS II. In accordance with this. \NzzN Diazot. C10H4< = Xylidine Ponceau. p-amidodimethyl aniline ought to be obtained on reduction. C10H5<f = Croceine Orange. /OH C 6 H 5 . . thus forming. Aniline + croceine acid (jS-Naphthol sulphonic acid) /OH (CH 3 ) 2 . then. in the above case. with the addition of 4 atoms of hydrogen. \(SO3H)2 Diazot. \SO«H Diazot. on the other an amido-group is introduced into the second component. Benzidine + 2 mol. The reaction takes place as follows: From two molecules of the diamine there is split 'off on oxidation with ferric chloride .OH Diazot." NziN. prepared from the benzidine bases (see page 204). and t h e n united with an amine or phenol. this is diazotised. this is diazotised. In conclusion.C 6 H 3 / I ^°* 0H =Chrysamine.C6H/ • • ' %:O. C6H4. Azo dyes which contain two "chromophore groups. a-naphthionic acid /OH C 6 H 4 . "Biebrich scarlet" is obtained i n this way. can be prepared. two methods may be employed: (i) The starting-point is an amido-azo-compound which already contains one azo group. To this class belong the important dyes of the Congo group. the formation and consequent reduction of an azo dye with the introduction of an amido-group into a phenol or amine is of practical value. salicylic acid These Congo dyes possess the noteworthy property of colouring vegetable fibres (cotton) directly. with all other azo dyes. by diazotising the disulphonic acid of amidoazobenzene. t h e cotton must be mordanted before dyeing. fcN ^\ N _ K -^ Diazot. and the bisdiazocompound is combined with two molecules of an amine or phenol.N=N. e. the above dye-stuff reaction (which may be us«d for detecting the smallest amount of hydrogen sulphide) is technically carried out on the large scale.N=N. whereas. Benzidine + 2 mol.234 SPECIAL PART In some cases.: /NH3 1 ° H ? = Congo.g.ClftH«. C « H Z " .SO«H . Diazot.OH. a n d combining it with /?-naphthol: . Amidoazobenzene disulphonic acid + /3-naphthol (2) A diamine is the starting-point. a n d which are called dis.or tetr-azo dyes. for the manufacture of the important methylene blue. by a hydrometer). REACTION: PREPARATION OP A DIAZOAMTDO-COMPOUND EXAMPLES: Diazoamidobenzene from Diazobenzenechloride and Aniline 1 Dissolve IO grammes of freshly distilled aniline in a mixture of ioo ex. The solution is cooled with ice-water. A solution of 10 grammes of aniline in 50 grammes of water is previously prepared according to the directions already given. of water. H •N(CH3)2. *2i. 2^7.c. and diazotised with a solution of 8 grammes of sodium nitrite in 50 c. as follows: /N(CH3)2 H H. a derivative of thiodiphenylamine.AROMATIC SERIES 235 one molecule of ammonia. gr. and that quantity of concentrated hydrochloric acid corresponding to 12 grammes anhydrous hydrochloric acid (determine the sp. .. in the manner already described. 2 See page 230. and exactly the theoretical amount of hydrochloric acid^2 1 A. of water.fl]Cl I—+' NTS Mcthylene blue 13. there is formed from this. by the oxidising action of ferric chloride. while a derivative of diphenyl amine is formed: /N(CH S ) 2 /N(CH 3 ) 2 C6H4 6 C6H4 I \N(CH3)2 In the presence of hydrogen sulphide and hydrochloric acid. +0 /N(CH3)2 C 6 H. N = N . The diazoamido-compounds are yellow substances which do not dissolve in acids. if they are heated rapidly they puff up suddenly and decompose. and form a phenol and an amine: = C^H5. Melting-point. to the mixture of the diazocompound with aniline hydrochloride. in the formation of an azo dye. After standing half an hour. 50 grammes of sodium acetate are dissolved in the least possible . NH . C6H5 + HC1 Diazoamidobenzene Mixed diazo-compounds may also be prepared by causing the diazoderivative of an amine to combine with another amine: /CH 3 C6H5. the cooled solution is added. as in the formation of the azo dyes.OH = C 6 H 5 . If. almost theoretical.NH 2 . an amido-hydrogen atom is eliminated. NzzN. Further. CH3 + HC1 Benzenediazoamidotoluene Diazo-compounds combine only with the free amines to form diazoamido compounds. e. Yield. washed several times with water. 98 0 . If one molecule of a diazo-compound is allowed to act on one molecule of a primary amine. and may be recrystallised without decomposition. In this case. Cl + C6H5. NH 2 = C6H5. They are far more stable than the diazo-compounds. NH. and is filtered off with suction. they decompose with evolution of nitrogen. N 2 . C 6 H 4 .236 SPECIAL PART after it has been well cooled with ice-water. N 2 . upon which the organic residues combine. Still. Cl + C 6 H 4 / = C6H5. In their reactions they behave like a mixture of a diazo-compound and an amine. with stirring. the diazoamidobenzene separates out..g. is added to the diazo-solution. one of the benzene-hydrogen atoms of the amine is eliminated : C 6 H 5 . so that a compound containing a chain of three nitrogen atoms is formed. the acid radical of the former unites with the hydrogen atom of the latter. well pressed out on a porous plate. and recrystallised from ligro'in. they are boiled with hydrochloric acid. the object of the addition of sodium acetate at the end of the reaction (see above) is to set free the base from aniline hydrochloride. with stirring.amount of water. C6H5 + HC1 = C6H5. The diazo-compounds also have the power of combining with secondary amines to form diazoamido-compounds. NH. C6H5 = C6H5. Under the influence of nitrous acid. they decompose. N = N . N H . they form a hydrazine: C 6 H 5 . in addition to the reaction-product of the diazo-radical. N . the Sandmeyer reaction takes place: C6H5. NH. N 2 . Cl + C6H5. NzrN. 239. C6H4. transformation to the isomeric amidoazocompound takes place: C6H5. into two molecules of a diazo-compound: C6H5. recently however they have been obtained by the direct decomposition of the diazo-fluorides. 243. N H .AROMATIC SERIES 237 On heating with cuprous chloride and hydrochloric acid. NH2 + N2 By reduction with acetic acid and zinc dust. NH. If they are gradually warmed with hydrofluoric acid. N=:N.c/\ci NI are of especial value for preparations. NH2 But. Fl + C 5 H n N + N2 Benzenediazopiperidine Fluorbenzene In this way it has been possible to prepare the aromatic fluorides. the amine residue being diazotised. — the combinations with an alkaloid base. C6H5 + HNO2 + 2 HC1 = 2 C6H5. N ~ N . In accordance with the older views it was believed that the aromatic fluorides could not be obtained from the diazo-compounds in the same way in which the analogous chlorides. . + C6H5. they are decomposed with the evolution of nitrogen into piperidine and a fluoride:* C6H5. Cl + 2 H2O If a diazoamido-compound is warmed with an amine in the presence of some amine hydrochloride. and iodides are prepared . bromides. iA. NizN. there is always formed one molecule of an amine. C6H5 + 2 H2 = C6H5. N = N . NH2 Amidoazobenzene The next preparation deals with this reaction. piperidine C 5 H U N: CH2 2 H. NH . C5H10 + HF1 = C a H 5 . on long standing. these are filtered off.. heated in a large dish with a large quantity of water (about a litre). NH 2 + C6HA. If aniline hydrochloride is not at hand. at 45°. After cooling. If a diazoamido-compound is heated with an amine and some amine hydrochloride. the mixture is then heated. the pasty mass of crystals separating out is filtered on glass-wool. Melting-point. REACTION: THE MOLECULAR TRANSFORMATION OF A DIAZOAMIDO-COMPOUND INTO AN AMIDOAZO-COMPOUND EXAMPLE: Amidoazobenzene from Diazoamidobenzene To a mixture of 10 grammes of crystallised diazoamidobenzene. and 5 grammes of pulverised aniline hydrochloride. and hot water is added until the liquid begins to be turbid. and the undissolved precipitate remaining is completely solid. the free base filtered off. dilute acetic acid is added. prepare it by adding aniline to concentrated hydrochloric acid. the hydrochloride is warmed with dilute ammonia. The most probable cause of the reaction is that the amine residue of the diazoamido-compound unites with a benzene-hydrogen atom of the amine hydrochloride. From the filtered solution. add 25 grammes of freshly distilled aniline. until all the aniline has passed into solution. not with water. and then spread in thin layers on a porous plate. 6-8 grammes. with stirring. This is filtered off. pressed firmly together on the filter with a pestle.238 SPECIAL PART 14. 12 7-128 0 . It is then transferred to a larger vessel. washed with water. In order to obtain the free amidoazobenzene. on the water-bath. C 6 H. steel-blue crystals of amidoazobenzene separate out. NH 3 Amidoazobenzene . it goes over to an amidoazo-compound. one hour. upon which the diazo-residue unites with the residue of the amine salt to form amidoazobenzene: = C 6 H 5 . with frequent stirring. and treated with water. dissolved in alcohol by heating. Nz=N. and gradually treated with hydrochloric acid until the greatest portion of the precipitate is dissolved. and washed with dilute hydrochloric acid. Yield. contained in a small beaker. finely pulverised. 125. The amidoazobenzene hydrochloride came into the market formerly. which in the form of its alkali salts finds application as a dye under the name of " Acid Yellow. and the next morning it is again cooled and stirred. 268. 69). the addition of the dichromate must be discontinued for a short time and a few pieces of ice thrown into the beaker. as a yellow dye. After the mixture has been allowed to stand until midday. from the diazo-compound of this dye. 2283. which always happens when the para position is unoccupied. the amidoazobenzene is still used for the preparation of the Induline dyes. 215." or "Fast Yellow. REACTION: OXIDATION OF AN AMINE TO A QUINONE EXAMPLE : Quinone from Aniline l To a solution of 25 grammes of aniline in a mixture of 200 grammes of concentrated pure sulphuric acid and 600 c. under the name of u Aniline Yellow. . of water is added. p-phenylene diamine and aniline are obtained. while a solution of 50 grammes of sodium dichromate in 200 c. of water (Fig. add gradually. Should the temperature rise above ro°. and thus there is a molecule of the amine hydrochloride present. 15. cooled to 50 by being surrounded with ice. they partially dissociate. 1467. of water contained in a thick-walled beaker (a small battery jar)." As already mentioned under the dis-azo dyes. Finally." At present. from a dropping funnel. 45. 20. so that a small amount of the hydrochloride may transform an indefinitely large amount of the diazoamido-compound.c. The transformation accordingly results in the formation of a compound in which the amido-groups are in the para position. which again causes the transformation. it is divided into two equal parts. 19. but there is prepared from it. The amidoazocompounds possess weakly basic properties.c. The reaction-mixture is then allowed to stand over night in a cool place. the new molecule of the amine formed in the reaction does. B. a mono. " Biebrich Scarlet" may be made-by combination with /3-naphthol. with constant stirring (use a small motor).AROMATIC SERIES 239 While the amidoazobenzene does not unite with hydrochloric acid. by heating with sulphuric acid. 27. it is scarcely used. If amidoazobenzene is reduced.or di-sulphonic acid.c. one of which is worked up into quinone as follows : In a large separating 1 A. but if their salts are treated with much water. a solution of 25 grammes of sodium dichromate in 100 c.354. Melting-point. Separation of coloured liquids). and the ether again distilled from the same flask as before. 25 grammes of potassium dichromate.240 SPECIAL PART funnel one half is treated with f its volume of ether. still. If the shaking is too vigorous.c. the ethereal solution is filtered through a folded filter. powdered extremely fine. In this case. they are filtered off and dried in a desiccator. of water . In order to obtain perfectly pure quinone. with stirring and good cooling. a rapid current of steam is passed over the crude product — it is not treated with FIG. proceed as above. 10-12 grammes. n6°\ Yield. water. and the two layers thus formed are carefully shaken together. But the reaction cannot be expressed in a simple equation . The water solution is again extracted with the condensed ether. where it crystallises in the form of goldenyellow needles. 25 grammes of aniline are dissolved in a mixture of 200 grammes of sulphuric acid and 800 c. then add. the pure quinone is carried over with the steam to the condenser and receiver. the potassium salt may be used for the oxidation. After allowing it to stand for half an hour. the layers will not readily separate. In other respects. as above. 69. the lower layer is run off (see page 44. If sodium dichromate is not at hand. and the ether distilled off (water-bath with warm water). On the next day add 50 grammes of this salt. it is always true that the amido-group and the hydrogen . Many primary aromatic amines yield quinones on oxidation with chromic acid. The quinone reaction can be used in doubtful cases to decide whether a compound . or sulphonic acid-group. m-xylidine. e. however. give satisfactory yields of quinones belonging to the next lower series: O HoC Pseudocumidine p-Xyloquinone But if the para position is occupied by an amido-.: C0H5.AROMATIC SERIES 241 atom in the para position to this are each replaced by an oxygen atom.NH2—^QHA Quinone < CH3 NH 2 2 2 Toluidine Tolyl quinone The tendency to form quinones is so great that even in cases where the para position to the amido-group is occupied by an alkyl (methyl) radical. like p-toluidine and asym.g. Indeed. this is eliminated and a quinone formed: X From these methods of formation it follows that the two quinoneoxygen atoms are in the para position to each other. the reaction is very incomplete. oxy-. as well as pseudocumidine. in the simplest cases. mesidine. the latter is split off and a quinone (poorer in carbon contents) is formed. OH p-CcH4< + O = CCH4O2 + H2O X)H /OH p-CGH^ _^QHA. the oxygen atoms are connected by two bonds. According to this conception. The two oxygen atoms are only singly united with the benzene-carbon atoms. The quinones can also be obtained very easily from p-dioxy-compounds as well as from the p-sulphonic acids of mon-acid phenols: . with the carbon atoms of the benzene nucleus. and are united to each other as in the peroxides. but they are derived from a dihydrobenzene.242 SPECIAL PART belongs to the para series. the quinones do not contain the true benzene ring. as in the ketones. The facts in favour of the first formula are these: In many reactions both of the . H and are regarded as the di-ketone derivative of this. According to the second formula. Two formulae for the quinones have been proposed — the Peroxideand Ketone-formula: O HC H H Peroxide formulae Ketone formulae According to the former the quinones still contain the true benzene ring with either three double or six centric bonds. Melting-point. (See the next preparation) e. it is passed in again and the mixture allowed to stand for some time as before. Since the hydroquinone solution may be extracted with ether with much greater ease than the quinone solution. REACTION: REDUCTION OF A QUINONE TO A HYDROQUINONE EXAMPLE: Hydroquinone from Quinone Conduct sulphur dioxide into the second half of the quinone solution obtained above. In support of the second formula is the fact that hydroxylamine acts directly on quinones.g. several times . 1690. p-dichlorbenzene is formed. but with a slight' decomposition. On reduction they take up two hydrogen atoms and pass over to hydroquinones. well pressed out on a porous plate.g. until the liquid smells intensely of the gas. as one observes in the preparation of quinone. In order to convert it into quinone it is dissolved in the least possible amount of water. they are easily volatile with steam. and since the hydroquinone is smoothly oxidised to quinone. It is then extracted with the ether distilled from the quinone in the preceding experiment. 8-io grammes. The quinones are yellow compounds.. Should the odour of sulphur dioxide vanish. with the formation of a mono. They are somewhat volatile even with the vapour of ether. possessing a characteristic odour. Thus.: ^pj C0H4O2 + H 2 = C 0 H 4 / . the well- . while the second formula would lead one to expect a tetra-chloride. and as just described the hydrociuinone may be obtained by repeated extraction with ether. Hydroquinonc 16. as on ketones. e.AROMATIC SERIES 243 oxygen atoms are replaced by two univalent atoms or radicals. Yield. by the action of phosphorus pentachloride on qufhone. the preparation of quinone may be done as follows: The entire quantity of the oxidation product is saturated with sulphur dioxide. then allow it to stand for 1-2 hours. the ether is evaporated or distillecj/and the hydroquinone. is crystallised with the use of animal charcoal from a little water.or di-oxime. to which is added 2 parts of concentrated sulphuric acid to 1 part of hydroquinone. with the evolution of hydrobromic acid. but the end is about 1 cm. After 50 grammes of benzene and 1 gramme of coarse iron filings (the bromine carrier) have been placed in the flask. 70). wide.244 SPECIAL PART cooled liquid is treated with a water solution of sodium dichromate until the green crystals of quinhydrone (an intermediate product between quinone and hydroquinone) separating out in the beginning have changed into pure yellow quinone.c. of water. the ice-water is removed for a short time. through the vertical tube there is added 40 c. All homologous quinones react in the same way. But as soon as even a weak gas evolution begins. long and i-J. After some time an extremely energetic reaction will begin.c. not too narrow. The hydroquinones are di-acid phenols. slightly warm water. which is completely absorbed by the water.and Di-brombenzene from Bromine and Benzene A wide-neck 250 c. Should the reaction not begin at once. the flask is at once cooled again. the upper end of which is closed by a cork bearing a glass tube. since . which dissolve in alkalies and show all the properties of phenols. 17. by a cork having a small canal in the side (Fig. The equation for the formation of hydroquinone from quinone has been given above. = 120 grammes of bromine: the narrow tube is immediately connected with the vertical tube. They are not volatile with steam. bent twice at right angles.c. and if necessary the flask is immersed for a moment in FIG. The other end is connected with a flask containing 250 c. The tube does not touch the liquid. 70.cm. above the surface. generally spontaneously. it is cooled in a large vessel (battery jar) filled with ice-water. REACTION: BROMINATION OP A N AROMATIC COMPOUND EXAMPLE : Mono. flask is connected with a vertical tube 50 cm. The reaction-product is washed several times with water and then distilled with steam. As soon as crystals of dibrombenzene separate out in the condenser. dried with calcium chloride. while still warm. e.) A portion of the hydrogen of the aromatic hydrocarbons is very easily replaced by bromine.. Yield.. hydrobromic acid. and subjected to a fractional distillation . and the portion going over between 150-160° collected. coarse colourless crystals of p-dibrombenzene are obtained. is purified as described in the Inorganic Part.AROMATIC SERIES 245 otherwise the reaction easily becomes too violent. on a porous plate. the cause is found in the fact that the iron filings used were too fine. and another portion is always acted upon farther. it may happen. is poured. This is again distilled. The boiling-point of the pure monobrombenzene is 15 50. When the main reaction is over.H8Br + HBr C0H0 + 2 Br2 = CfiH<Bra + 2 HBr .g. the ice-water is removed. In other experiments use coarser filings or small iron nails. the aromatic bromides are readily prepared in this way. especially in the presence of a carrier. (See page 345. On crystallising from alcohol. Thus in the example above cited. and after cooling is pressed out. the flask dried and heated over a small flame until the red bromine vapours are no longer visible above the dark-coloured liquid. besides the principal product. that all the hydrogen atoms may be replaced by bromine. even at low temperatures . According to the amount of bromine used one or more hydrogen atoms may be substituted.. which melt at 890. while in the aliphatic series the direct substitution of bromine is not used as a preparation method for alkyl bromides. on a watch-glass. with the formation of a higher bromine substitution product. 60-70 grammes. The by-product. The liquid monobrombenzene is separated from the water. the receiver is changed and the distillation continued until all the dibrombenzene has passed over. the portion passing over between 140-1700 is collected separately. A single bromide. together with the separately collected dibrombenzene. but rather a portion of the hydrocarbon is brominated short of the theoretical action. particularly with benzene under the influence of an energetic bromination. is never formed. even on using only the theoretical amount of bromine. Should this happen in spite of the cooling.HU + Bra = C. a small quantity of dibrombenzene is formed: C. The residue boiling above 1700 remaining in the flask after the two distillations. monobrombenzene. 246 SPECIAL PART In most cases, however, the principal product may be separated from the by-product without difficulty by distillation or crystallisation. Since the hydrogen atoms substituted by bromine combine with bromine to form hydrobromic acid, therefore, for the introduction of each bromine atom, a molecule (two atoms of bromine) must be used. The introduction of bromine can be essentially facilitated by the use of a so-called bromine carrier. As such, the bromides of metalloids, or metals, are used; (1) either in the already prepared condition, or (2) they can be generated from their elements in the reaction. To the first class belong ferric bromide and aluminium bromide. The action of ferric bromide depends on the fact that on being reduced to ferrous bromide, it yields bromine in statu nascendi: FeBr 3 = FeBr2 4- Br, Ferric bromide Ferrous bromide Since the ferrous bromide unites with bromine again, to form ferric bromide, a small quantity of this has the power to transfer an indefinitely large quantity of bromine: FeBr2 + Br = FeBr 3 . Instead of ferric bromide, ferrous bromide or anhydrous ferric chloride may be used. The latter decomposes with hydrobromic acid to ferric bromide and hydrochloric acid: FeCl3 + 3 HBr = FeBr 3 + 3 HC1. The activity of aluminium bromide is explained by the fact that it unites with the hydrocarbon to form a double compound which is more capable of reacting with other substances than the hydrocarbon itself. To the second class belong iodine, sulphur, phosphorus, iron, aluminium, etc. If these elements are added to the brominating mixture, the corresponding bromides are formed, e.g.: I + Br = IBr 1 . While these give up all their bromine, or a portion of it, as is the case with ferric bromide, in the atomic condition, the residue again unites with bromine, and as above, a small quantity of the carrier may transfer large quantities of atomic bromine. Bromine can also act on aromatic hydrocarbons to form addition products, since it may be added in one, two, or three molecules, and thus break up the double or centric union- Thus, e.g., the hexabrom1 Qompare page i^it AROMATIC SERIES 247 addition product, CnH0Brfi, is obtained from the action of bromine on benzene in the sunlight. Since the addition products render difficult the purification of substitution products, especially on distillation (they decompose when distilled), it is often necessary to remove them before the purification, by long boiling with alcoholic caustic potash, t>r alcoholic caustic soda. Under these conditions, one-half of the bromine atoms added in common with the same number of hydrogen atoms are abstracted as hydrobromic acid; the residue of the molecule is converted into a substitution derivative, which is not troublesome in the purification: CHB CHB On brominating benzene, the same products will be formed, whether the temperature is high or low, but when its homologues are treated with bromine, the nature of the products depends upon the temperature. As will be pointed out more fully, under the chlorination of toluene, the law holds here, that at low temperatures the bromine enters the ring; at high temperatures, the side-chain, e.g.: /CH3 C 8 H,. CH S + Br2 = C(iH4< + HBr Ordinary temperature Boiling temperature Bromtoluene Bewzylbromidc QHj.CH,, + Bra = C(5Hrt.CH2. Br + HBr. The aromatic bromides which contain bromine in the benzene nucleus are either colourless liquids or crystals, which in contrast with the side-chain substituted isomers in part possess an aromatic odour, and their vapours do not attack the eyes and nostrils. The bromine is held very firmly in them, more firmly than in the aliphatic bromides, and cannot be detected by silver nitrate. While the aliphatic bromides, as mentioned under bromethyl, decompose with ammonia, alcohol, alkalies, etc., to form amines, ethers, alcohols, etc., respectively, these reagents do not act on the aromatic bromides. The bromides containing the bromine in the side-chain, behave like their aliphatic analogues. By the action of sodium amalgam, the bromine may be replaced by hydrogen, e.g. : C e H,.Br + H, = C0Hfl From the Amalgam The aromatic bromides are of synthetical importance, especially for the building up of homologous hydrocarbons and the preparation of carbonic acids: 248 SPECIAL PART C 6 H 5 . Br + BrC2H5 + Na2 = C 0 H 5 . C2HK + 2 NaBr C6H5. Br + Na2 + C0 2 = C (l H 5 . CO. ONa + NaBr. The next preparation will take up the first of these reactions in detail. The hydrocarbons and most of their derivatives, like nitro-, amidocompounds, aldehydes, acids, etc., may be brominated with greater or less ease. At this place, the various modifications by which the bromination may be effected will be mentioned. If a substance is very easily brominated, the bromine may be used in a diluted condition. For this purpose, either bromine water or a mixture of bromine with carbon disulphide or glacial acetic acid may be employed. In many cases a bromination may be very well effected by using gaseous bromine. The method of procedure is as follows: ^ ^ e substance is spread out in thin layers on a watch-glass and placed under a glass bell-jar, under which is also a small dish containing bromine. If it is desired to cause bromine to act gradually, it is allowed to drop from a separating funnel, in concentrated form or in solution, on the compound to be brominated. If an extremely slow and very careful bromination is desired, the bromine may be allowed to flow drop by drop from a siphon-shaped capillary tube. If bromination takes places with difficulty, the brominating mixture is heated either in an open vessel or in a sealed tube. In the first case the condensing apparatus cannot, as usual, be connected to the flask with a cork or rubber stopper, since this is soon attacked and destroyed by the bromine. Instead, the condenser is well wrapped with asbestos twine "and then pushed into the conical part of the neck of the flask, the asbestos being pressed in with a knife. A condenser of the kind represented in Fig. 71 can also be used. A long tube c, sealed at one end, is closed by a two-hole FIG. 71. cork, through one of which passes a long glass tube reaching almost to the bottom a; the other bear& a short tube just passing through the cork. Water is caused to flow through a; it flows AROMATIC SERIES 249 out of b. This cooling apparatus is suspended in the heating-flask, which is selected with as long a neck as possible. 18. REACTION: FITTIG'S SYNTHESIS OP A HYDROCARBON EXAMPLE : Ethyl Benzene from Brombenzene and Bromethylx In a dry, round, -.}-litre flask, provided with a long reflux condenser (the flask is supported on a straw ring in an empty waterbath), place 27 grammes of sodium, cut in scales as thin as possible with a sodium knife, and add 100 c.c. of alcohol-free, dry ether prepared as described below. As soon as this has been completely dried by the sodium, which may be recognised by the fact that the upper surface is no longer disturbed by wavelike motions (after several hours' standing), pour through the condenser a mixture of 60 grammes of brombenzene and 60 grammes of bromethane, and allow to stand until the next day. Should the liquid begin to boil gently, which may easily happen at a summer temperature, cold water is poured into the water-bath. Water is not allowed to run through the condenser over night. During the reaction, the bright sodium will be changed to a blue powder, and an ethereal solution of ethylbenzene is formed. The ether is then distilled off on a water-bath, and the condenser is replaced with an air condenser 40-50 cm. long and 1 cm. wide, containing a short bend. After the flask has been placed in an oblique position, the extreme end of its neck is clamped loosely, and the ethylbenzene is distilled from the sodium bromide and sodium by a large, luminous flame, which is kept in constant motion. With the use of a Linnemann apparatus, the crude product is finally subjected to two distillations. The boiling-point of pure ethylbenzene is 1350. Yield, about 25 grammes. The residue of sodium bromide and sodium remaining in the flask must be handled with extreme caution. Water must not be added to it, nor must it be thrown into the sink or waste-jars, nor allowed to stand a long time ; it is better to throw the flask, which 1 A. 131,303, 250 SPECIAL, FART cannot be used again, and its contents into some open place. The sodium residue may be rendered harmless by throwing water on it from a great distance. Preparation of Anhydrous, Alcohol-free Ether Shake 200 grammes of commercial ether in a separating funnel with half its volume of water; the latter is allowed to run off, and the operation repeated a second time with a fresh quantity of water, by which the alcohol is removed. The ether is dried by standing over calcium chloride, not too little, two hours. It is then filtered through a folded filter, and can now be used for the above reaction. Fittig's synthesis of the aromatic hydrocarbons is the analogue of Wurtz1 synthesis of the aliphatic hydrocarbons, e.g.: 2 C2HSI + 2 Na = C2H5. C2H, + 2 Nal Ethyl iodide Butane C 6 H 5 . Br + C2H5Br + 2 Na = C,;H5. C 2 H 5 + 2 NaBr. Ethylbenzene The bromides of the homologues of benzene react in a similar way, e.& : C6H/ + ICH3 + Na2 = C 6 H / + NaBr + Nal. >CH.g >Br Bromtoluenc Xylenc The three isomeric bromtoluenes do not react with the same ease. While the p-bromtoluene gives a good yield of p-xylene, the o-compound does not give good results, and the m-compound generally forms no xylene. Two alkyl residues can also, in many cases, be introduced into a hydrocarbon simultaneously, e.g.: /Br /CH8 p-C 6 H/ / 4- 2ICH8 + 2 Na2 = p-C6H4< + 2 NaBr +,2 Nal. The great number of hydrocarbons which may be prepared by Fittig's reaction is apparent from the above examples. The value of the reaction is still further increased by the fact that a halogen atom in the side-chain of an aromatic hydrocarbon also reacts in the same way. AROMATIC SERIES 251 Though the halogen cannot be replaced by a methyl or ethyl radical, yet the reaction for the introduction of the higher alkyl residues is of great service, e.g.: QII«.CH 2 C1 + CH 3 .CH 2 .CHoBr + Na2 Henzyl chloride Propyl bromide = QH,,. CH 2 . CH 2 . CH 2 . CH 3 + NaCl + NaBr. Butylbcnzene Also by means of this reaction, two aromatic residues may be made to combine, and thus form the hydrocarbons of the diphenyl series, e.g.: 2 C0H3. Br + Na2 = C(!H,. C«H5 + 2 NaBr. Diphenyl Finally, the hydrocarbons of the dibenzyl series can also be prepared, e.g. : 2 C(5H3. CIIaCl + Na i = C(JH,. CH 2 . C H r C6H5 + 2 NaCl. Dibenzyl In conducting operations involving the Fittig reaction, various modifications may be introduced, according to the ease with which the reaction takes place. If the reaction occurs at the ordinary temperature easily, then an indifferent diluent like ether, ligro'in, carbon disulphide, or benzene is employed. These substances are not alike in their activity, since ligro'in and benzene generally prolong the reaction, and on this account find application in a very energetic reaction; ether does not retard the reaction, but causes it to be more regular. At times, the reaction-mixture will not act, even on long standing. In this case, the reaction can frequently be started by a short heating, or the addition of a few drops of ethyl acetate. Since the use of this compound, at times, causes a very stormy action, it is more advantageous to wait for the reaction to begin spontaneously, even if a long time is necessary. In syntheses which are moderately difficult, the reaction-mixture, treated with a diluent, can be heated on the water-bath or in an oil-bath; while, if the reaction takes place with great difficulty, the mixture, generally without dilution, must be heated in an oil-bath. In the latter case, the reaction may be still further facilitated by heating under pressure of a mercury column. By this means, it is possible to heat the reacting substances in an open vessel above their boiling-points. (Fig. 72.) AROMATIC SERIES 253 19. REACTION: SULPHONATION OF AN AROMATIC HYDROCARBON (I) EXAMPLE: (a) Benzenemonosulphonic Acid from Benzene and Sulphuric Acid1 (3) Sulphobenzide. Benzenesulphonchloride. Benzenesulphonamide (a) To 150 grammes of liquid fuming sulphuric acid, containing from 5-8 °/o of anhydride, placed in a 200 c.c. flask provided with an air condenser, gradually add, with good shaking and cooling with water, 40 grammes of benzene ; before the addition of a new portion, always wait until the last portion, which at first floats on the surface of the acid, dissolves on shaking. The sulphonation requires about 10-15 tninutes. The reaction-mixture is then added, with stirring, drop by drop, from a separating funnel, to three to four times its volume of a cold, saturated solution of sodium chloride contained in a beaker. In order that the solution may not be heated above the room temperature, the beaker is placed in a large water-bath filled with ice-water. After some time, but with especial ease when the walls of the vessel are rubbed with a sharp-edged glass rod, the sodium salt of benzenesulphonic acid separates out in the form of leaflets of a fatty lustre; the quantity is increased, on long standing, to such an extent that the beaker may be inverted without spilling its contents. If the separation of crystals does not begin, 10 c.c. of the liquid is shaken in a corked test-tube, and cooled by immersion in water. The solidified content of the tube is then added to the main quantity in the beaker. In summer, at times, it may require a several hours' standing before the separation of crystals is ended. The pasty mass of crystals is then filtered off with suction on,a Biichner funnel, firmly pressed together with a pestle, and washed with a little saturated sodium chloride solution. To obtain the salt perfectly dry it is transferred to a linen bag and well squeezed under a screw-press. After being pulverised it 1 P. 31, 283 and 631; A. 140, 284; B. 24, 2121. 254 SPECIAL PART is heated to dusty dryness in an air-bath at no°: Yield, about ioo grammes. If even after long standing an abundant separation of crystals does not take place, the cause is probably due to the large percentage of anhydride in the fuming sulphuric acid. Under these conditions it is diluted with concentrated acid, and the experiment repeated. If on the other hand the acid is too weak, the benzene will not dissolve in it. In this case, during the sulphonation the mixture is not cooled, and the reaction is allowed to take place at 40-5 o°. In order to obtain pure sodium benzenesulphonate, 5 grammes of the crude product is crystallised from absolute alcohol, upon which it is noticed that the sodium chloride mixed with it is insoluble in alcohol. (£) In order to obtain the by-product, sulphobenzide, 30 grammes of the pulverised salt is wanned with 50 ex. of ether, filtered with suction while hot, and washed with ether. After evaporating the ether, a small amount of a crystalline residue is obtained ; this is recrystallised in a test-tube from ligroin. Melting-point, 1290. To prepare benzenesulphonchloride from sodium benzenesulphonate, the extracted salt and unextracted salt are treated in a dry flask (under the hood) with finely powdered phosphorus pentachloride (for 3 parts dry sodium benzenesulphonate, use 4 parts phosphorus pentachloride). Mix by thorough shaking. The mixture is warmed J to ^ hour on an actively boiling water-bath. The cold reaction-product is then poured gradually into ice-water in a flask (use ten times the weight of the sodium salt) ; it is shaken up from time to time, and, after standing for two to three hours, the salphonchloride is taken up with ether and the generally turbid ethereal solution filtered ; the ether is then evaporated off. Yield, 40-50 grammes. In a porcelain dish 10 grammes of finely powdered ammonium carbonate are treated with about 1 c.c. of benzenesulphonchloride, and rubbed together intimately; the mixture is heated, with good stirring, over a small flame, until the odour of the sulphonchloride AROMATIC SERIES 255 has vanished. After cooling, it is treated with water, filtered with suction, washed several times with water, and the benzenesulphonamide crystallised from alcohol to which hot water is added until turbidity begins. Melting-point, 15 6°. Under the sulphonation of aniline it was mentioned that the aromatic compounds differ from the aliphatic compounds in that they can be sulphonated by the action of sulphuric acid; i.e. the benzene-hydrogen atoms are replaced by the sulphonic acid group, SO.{H. Thus the above reaction takes place in accordance with the following equation: /OH C6H6 + SO/ \OH = C6H5. SO3H 4- H2O Since, in the sulphonation, an excess of sulphuric acid is always used, after the reaction is complete it is necessary to separate the sulphonic acid from the excess of sulphuric acid. Many sulphonic acids, especially those of the hydrocarbons, are very easily soluble in water, so that the pure acid cannot be separated out on mere dilution with water, as is the case with sulphanilic acid. There are three methods in common use for the isolation of sulphonic acids soluble in water. The sulphonic acids obtained most easily are those difficultly soluble in cold sulphuric acid. In this case it is only necessary to cool the sulphonating mixture, and filter off the sulphonic acid separating out, with suction over asbestos or glass-wool. A second method consists in allowing the sulphuric acid solution to flow into a saturated solution of common salt; in many cases the difficultly soluble (in sodium chloride solution) sodium salt of the sulphonic acid separates out. Frequently it is more advantageous to use sodium acetate, potassium chloride, ammonium chloride, or other salts, instead of sodium chloride. Almost all soluble sulphonic acids, in the form of their alkali salts, can be separated by these two methods in the shortest time. In dealing with a new substance, preliminary experiments with small quantities of the substance are made to determine which salt is best adapted for the separation. The third method, which is the one generally applicable, depends upon the property of sulphonic acids, of forming soluble salts of calcium, barium, and lead in contradistinction to sulphuric acid. If the sulphuric acid solution, diluted with water, is neutralised with the carbonate of one of these metals and then filtered, the filtrate contains only the corresponding salt of the sulphonic acid, while the sulphuric acid in the form of calcium, barium, or lead sulphate remains on the 2$6 SPECIAL PART filter. If the alkali salts of the sulphonic acids are desired, the water solution of one of the above salts is treated with the alkali carbonate until a precipitate is no longer formed. The precipitate is filtered off, and the pure alkali salt of the sulphonic acid is obtained in solution, which, on evaporation to dryness. yields the salt in the solid condition. In order to obtain the free sulphonic acid, the lead salt is prepared and then decomposed with sulphuretted hydrogen. The sulphonic acids of the hydrocarbons are generally colourless, crystallisable compounds, very easily soluble in water, behaving like strong acids. By heating with hydrochloric acid, under pressure if necessary, or by the action of steam, the sulphonic acid group may be split off, e.g.: QH 5 . SCX.H + H,O = CGHtf + H2SO4 This reaction is of importance in many cases for the separation of hydrocarbon mixtures. If under certain conditions one hydrocarbon is sulphonated, and another is not, the latter can be separated from the former by removing the sulphuric acid solution of the sulphonic acid of the first and from this the original hydrocarbon may be regenerated by one of the methods mentioned. Of particular importance is the behaviour of sulphonic acids when fused with caustic potash or caustic soda, by which the sulphonic acid group is eliminated and a phenol formed: QH 5 . SO.,K + KOH = C6H5.OH + K.,SOS With benzenesulphonic acid this important reaction does not take place smoothly; for this reason the directions for carrying it out practically will be given later in another place (see /3-naphthol). Polyacid phenols may also be obtained from poly-basic sulphonic acids. The formation of m-dioxybenzene or resorcinol from benzenedisulphonic acid is of practical value: .OH C6H4(SO3K)2 + 2 KOH = C6H / + 2 K2SO5 NDH If an alkali salt of a sulphonic acid mixed with potassium cyanide or potassium ferrocyanide is subjected to dry distillation, the sulphonic acid group is replaced by cyanogen and an acid-nitrile is obtained, e.g.: QH 5 . SOjK + KCN = C e H 5 . CN + KjSO^ Bcnxooitrilc AROMATIC SERIES 257 e^sulphonic acids behave toward phosphorus pentachloride like the carbonic acids, with the formation of acid-chlorides: C6H5. SO3Na + PCi5 = C6H5. SO2. Cl + NaCl + POCI, The sulphonchlorides differ from the carbonic acid chlorides, in that they are not decomposed by cold water. In order to separate them from the phosphorus oxychloride, the mixture is generally poured into cold water; after long standing the oxychloride is converted into phosphoric acid, and the acid-chloride insoluble in water is obtained by decanting the water or extracting with ether; or in case it is solid, by filtering. The sulphonchlorides are generally distinguished by a very characteristic odour. They can be distilled in a vacuum only, without decomposition. Treated with ammonia they form sulphonamides, which crystallise well and are used for the characterisation of the sulphonic acids: NH3 = C6H5. SO«. NH2 + HC1 In the sulphonamides, in consequence of the strongly negative character of the X.SO2-group, the hydrogen of the amido-group is so easily replaced by metals, that they dissolve in water solutions of the alkalies to form salts of the amide. (Try it.) If a sulphonchloride is allowed to stand a long time with an aliphatic alcohol, a sulphonic acid ester is formed, e.g.: C6H5. SO2. Cl + C2H5. OH = C6H5. SO2. OC2H, + HC1 Bcnzencsulphonic ester If this is now warmed with an alcohol, an aliphatic ether is formed, with the generation of the sulphonic acid, e.g.: C6H5. SO 2 . OC2H5 + C2H5. OH = C6H,,. SO3H 4- C , H 5 . 0 . C2H5 The formation of ether in this case is analogous to the formation of ethyl ether on heating ethyl sulphuric acid with alcohol: + C2H5. OH = HjSO4 + C 2 H 5 .0. C2H5 N}H Since this reaction is continuous, and since the benzene sulphonic add formed in the reaction is a weaker add than sulphuric add, and conses % 1585. and without further heating by the flame. The reaction is conducted with cooling. in many cases. SO3H + HC1 2 0 . at the room temperature. REACTION: REDUCTION OP A SULPHONCHLORIDE TO A STJLPHDSnC ACID OR TO A TBIOPHENOL EXAMPLES: (a) Benzenesulphinic Acid. flask provided with a short reflux condenser and a dropping funnel.142.g. according to the conditions. e.258 SPECIAL PART quently does not carbonise the alcohol like sulphuric acid. gradually allow to flow in from the funnel. the operation may be continued for a long time uninterruptedly. with thorough 1B. SO3H = C 6 H 5 . the reaction takes place in accordance with the following equation: C6H6 + C\. either ordinary concentrated sulphuric acid or the so-called monohydrate or fuming sulphuric acid of various grades is used. or with heating.1 (b) Thiophenol 2 (a) Heat 40 grammes of water to boiling in a 300 e x . If the sulphonation is effected as above with fuming sulphuric acid. . In some cases it is of advantage to use chlorsulphuric acid instead of sulphuric acid. add 10 grammes of zinc dust. 119. To facilitate the elimination of water. phosphorus pentoxide or potassium sulphate may be added to the sulphonating mixture. « A.For these reasons recently attempts have been made to employ the aromatic sulphonic acids for the technical preparation of ether. : +H 2 O 3 Diphenylsulphone = Sulphobenzide For sulphonating purposes. besides the sulphonic acid a small quantity of sulphone is formed. acidified with dilute sulphuric acid. The mixture is then heated a fe\y minutes over a small flame. rectified. upon which the free benzenesulphinic acid separates out in colourless crystals. of water. Melting-point. care is taken that there are no flames in the neighbourhood of the flask in which the reaction is conducted. The insignificant-looking gray precipitate is the reaction-product. after cooling. dried over anhydrous Glauber's salt/and. and not the filtrate. 1730. and. the sulphonchloride is allowed to flow in gradually from the dropping funnel.AROMATIC SERIES 259 shaking. 83-84 0 . The thiophenol formed is distilled over with steam. the substance is recrystallised from a little water. After filtering. it is extracted several times with ether. not quite to boiling. this is evaporated. {b) In order to convert the residue of benzenesulphonchloride obtained in Reaction 19 into thiophenol. filtered after cooling from the precipitate of zinc dust and the zinc salt of benzenesulphinic acid.c. The precipitate remaining on the filter is worthless. After each addition wait until the vigorous reaction accompanied by a hissing sound has moderated.) The heating is continued until most of the tin is dissolved. The precipitate is then heated for about ten minutes. it is heated on a waterbath with granulated tin and concentrated hydrochloric acid. and the precipitate washed several times with water. (To 1 part of the chloride use 2\ parts of tin and 5 parts of concentrated acid. and then filtered with suction. after the evaporation of the ether. Should the free acid not separate on acidifying the sodium salt. This is evaporated to about one-half its original volume. 15 grammes of benzenesulphonchloride in small portions. in fcase it does not solidify of itself. which can be thrown away. in a large flask provided with a long reflux condenser and dropping funnel. and the residue. while the filtrate contains the sodium benzenesulphinate in solution. extracted with ether. is rubbed with a glass rod and then recrystallised. otherwise there may be-an explosion of the mixture . the separation is facilitated by rubbing the sides of the vessel with a glass rod. In the preparation of thiophenol. Boiling-point. with a solution of 10 grammes of dehydrated sodium carbonate in 50 c. or at least under a hood with a good draught.26O SPECIAL PART of oxygen and hydrogen. they form difficultly soluble salts with lead and mercury. Cl + ZnZn = C 6 H 5 .SH + 2 H2O + HCI The thiophenols are liquids of unpleasant odours. t Since the thiophenol possesses an extremely unpleasant odour. On fusing with potassium hydroxide. the experiment must not be carried out in the laboratory. SH + 2 H2O The thiophenols may also be prepared by the direct reduction of the sulphonchlorides: C6H5.ZnCl2 C6H5. In order to prepare the free sulphinic acid from a zinc salt.. and can. in the basement. causing tears. it is first converted into the easily soluble sodium salt by boiling with a sodium carbonate solution.S0 2 v )>Zn 4. and can be easily obtained by filtering off.C1 C 6 H 5 . If zinc dust is allowed to act on a sulphonchloride. Like the mercaptans of the aliphatic series. and the vapours attack the eyes.SO2C1 + 6H = C 6 H 5 . a thiophenol is finally obtained. since it produces a violent burning. The sulphinic acids differ from the sulphonic acids in that they are difficultly soluble in cold water. S O 2 / Zinc benzenesulphinate The zinc salts thus formed are insoluble in water. care must be taken not to allow the substance to come in contact with the skin. the higher members of the series are solids. the solution of the sodium salt is concentrated. therefore^ be recrystallised from water. Further.K + KOH = K2SOS + C6H6 If they are reduced. SO. but in a side room (hydrogen sulphide room). or in the open air. as above: CeH5.SO 2 . SO2H + 4 H = C 6 H 5 . the zinc salt of the sulphinic acid is formed : QH 5 . the sulphinic acids pass over to the hydrocarbons: C6H5. and the free acid is precipitated with dilute sulphuric acid. . SO. and filter. REACTION: SULPHONATION OP AN AROMATIC HYDROCARBON (II) EXAMPLE : p-Naphthalenesulphonic Acid A mixture of 50 grammes of finely pulverised naphthalene and 60 grammes of pure concentrated sulphuric acid is heated in an open flask in an oil-bath for 4 hours to 170-180 0 . the solution is carefully poured. then cool. of naphthalene. C6H5 + 2 H = 2 C6H5..S-S .S)2Pb In the air.: C6H5. S. treated with some ammonia. 6i°. If the alcoholic solution is treated with a few drops of thiophenol. pieces. SH Like the phenols the thiophenols have the power of forming ethers. S—S. 21.) Colourless needles of the disulphide remain. e.AROMATIC SERIES 261 EXPERIMENT: Dissolve mercuric chloride or lead acetate in a test-tube with alcohol by heating. into 1 litre of water. By reduction the disulphides are easily converted back to the thiophenols : * C6H5. and on treatment with oxidising agents like nitric acid. After cooling.SH + O = C 6 H 5 . a precipitate of the difficultly soluble salt is obtained. in case the filtration takes place very slowly. (Under the hood.g. and evaporated to dryness on the water-bath in a watch-glass. and the naphthalene not attacked is filtered off. the thiophenols are oxidised to disulphides: 2 C 6 H 5 .C 6 H 5 + H2O EXPERIMENT : A few drops of phenyl mercaptan are dissolved in alcohol. SCH3 = Thioanisol. C6H5. chromic acid. and possesses the composition represented by the formula : (C6H5. C6H5 = Phenylsulphide. Melting-point. only the turbid liquid is poured off from tk§ QQajse. The lead salt is yellow. etc. the mixture i§ . with stirring. Naphthalene is sulphonated on heating with sulphuric acid. after filtering. the expressed. but a mixture of two isomeric sulphonic acids: SOSH and . in which the six hydrogen atoms are equivalent.2g2 SPECIAL PART neutralised at the boiling temperature in a large dish with a paste of lime. After standing several hours at the ordinary temperature. it is dissolved in hot water. the crystals are filtered off. and the mother-liquor further concentrated. and the mixture of the two lots of crystals dried on the water-bath. washed once with a little water. and the solution gradually treated with a concentrated solution of 50 grammes of crystallised sodium carbonate until a test-portion filtered off no longer gives a precipitate with sodium carbonate. a single sulphonic acid. prepared by triturating about 70 grammes of dry slaked lime with water. and spread out on a porous plate. There is formed not as in the case of benzene. the precipitate of calcium carbonate is filtered off with suction. After cooling. turbid liquid. The filter-cloth is then folded together and thoroughly squeezed out in another dish . Yield. SO3H + HoO. the second crystallisation is filtered off. and the filtrate evapo*a. pressed firmly together with a pestle. after long standing. The mixture is filtered while hot as possible through a filter-cloth. is united with the main quantity. 60-70 grammes. not too thin.ted over a free flame until crystals begin to separate from the hot solution. generally. The solution is then evaporated in a dish over a free flame until a test-portion will solidify to a crystalline paste on rubbing with a glass rod. After the solution has been allowed to stand over night the calcium /3-naphthalenesulphonate is filtered off with suction. in accordance with the following equation: C10H8 + HjjgO* = C10H7. washed with water. which has been previously thoroughly moistened (see page 56) and the precipitate washed with hot water. In order to obtain the sodium salt. and consequently crystallises out first. Since the calcium salts of the two isomeric sulphonic acids possess a very different solubility in water. more of one than of the other acid is formed. since when fused with sodium hydroxide these acids yield naphthols of great importance for the manufacture of dyes. SO3)2Ca + Na2CO3 = 2 C10H7. and lead. SO3Na + CaCO3. The next preparation deals with this reaction. If the mixture is heated to ioo°. — at io° 1 part of the a-salt dissolves in 16. it is advisable not to evaporate the solution of sodium salt directly to dryness. while at 170° a mixture of the 3 parts of the /3-acid and 1 part of the a-acid is obtained. at higher an excess of the jft-acid. and 1 part of the /3-salt dissolves in 76 parts of water. upon which the a-salt remains dissolved in the mother-liquor. advantage is taken of the fact that sulphonic acids differ from sulphuric acid in that they form soluble salts of calcium. but to allow the more difficultly soluble /2-salt to crystallise out. a mixture of 4 parts of the a-acid and 1 part of the /3-acid is formed. into naphthalene and sulphuric acid. the calcium salt is prepared by neutralising the acid mixture with chalk or lime. For the conversion into naphthol the calcium salt cannot be used directly. The sulphonation of naphthalene to the a. The reactions of the naphthalenesulphonic acids are similar to those given above under benzenesulphonic acid. This method is followed technically on the large . In order to separate the sulphonic acids from the excess of sulphuric acid. For the separation of the sulphonic acid from sulphuric acid. it must first be changed into the sodium salt by treatment with sodium carbonate: (C10H7. — the /3-salt. as mentioned under benzenesulphonic acid. which is more difficultly soluble. since it is cheaper than lead carbonate or barium carbonate. a reaction which is explained by the fact that the sulphonic acid decomposes in the small amount of water always present. and that the former is then sulphonated to the /3-acid at the higher temperature (2000). barium.AROMATIC SERIES 263 According to the temperature at which the sulphonation takes place.scale as well as in laboratory preparations. can be separated by fractional crystallisation from the a-salt which remains in solution. .5 parts' of water.and ^-acids is carried out on the large scale in technical operations. It is still to be mentioned that the a-acid is converted into the /3-acid by heating with concentrated sulphuric acid to almost 2000. at lower temperatures an excess of the a-acid is obtained. In order to remove the last portions of the a-salt. 73). 73). The sodium hydroxide is broken in pieces about a centimetre in length. In order to be able to determine the temperature as exactly as possible. page 54.299. in which the bulb of the thermometer is immersed. or a cork is pushed over the case (Fig. treated with the water. REACTION: CONVERSION OP A SULPHONIC ACID INTO A PHENOL EXAMPLE : p-Naphthol from Sodium-p-Naphthalene Sulphonate and Sodium Hydroxide1 In order to convert sodiums-naphthalene sulphonate into /?-naphthol the proportions of the necessary reagents used are : 10 parts sodium-/3-naphthalene sulphonate. the lower end of which is protected by a case of copper or nickel. about 16 cm.264 SPECIAL PART 22. the upper portion is covered with several layers of asbestos board. the real reaction takes place. This is supported by a cork. fitting the case. Prep. 1867. no more of the salt is added. 1 part water. the flame is made somewhat larger. in diameter is a convenient size). Z. and the eyes by glasses. As soon as the temperature reaches 2800. with stirring. After the temperature is held 1 Et Fisckw-Klmg. and the sodium naphthalene sulphonate is gradually added. . After all the salt is added. at about 310*. long and 8 mm. wide. Since. until the temperature again reaches 2800. upon which the fusion becomes viscid with evolution of steam and frothing. and heated in a nickel crucible (a crucible 11 cm. the temperature falls somewhat. The stirring is done with a thermometer. with stirring. a troublesome spattering takes place. to 2800 (Fig. After each new addition. containing a narrow canal at the side. If the stirring is done with the case. high is placed in the case. until finally. the heating is continued with a somewhat smaller flame. a layer of oil 1 cm. as pure as possible. of Organic Compounds. the hand is protected by a glove. high and 8 cm. or the size of a bean. secured with wire. 30 parts sodium hydroxide. on fusion of the sodium hydroxide. After cooling. The naphthol is precipitated at the boiling temperature with concentrated hydrochloric acid (under the hood). but the alkali salt of it. half the weight of the sulphonate used. the fusion becomes liquid. from which. therefore. the solid mass is broken up and dissolved in water. The reaction just effected is in practice carried out on the largest scale in iron kettles to which stirring apparatus is attached. not directly obtained on fusion.and poly-sulphonic acid derivatives obtained by treatment with sulphuric acid find extensive application for . The portions of dark sodium naphtholate may be easily distinguished from the brighter caustic soda. After the removal of FIG. 73. the alkali sulphite is formed. e.g. SO3Na + 2 NaOH = C10H7 ONa + Na2SO3 Sodium naphtholate H2O The free phenol is. a fractionating flask with a very wide condensing tube is used. in a sodium hydroxide. As above indicated. The ethereal solution is dried over anhydrous Glauber's salt. or potassium hydroxide fusion of a sulphonic acid. : C10H7. and then the ether is evaporated in an apparatus similar to the one described on page 35 . ^-naphthol as well as its numerous mono. the naphthol remaining back is distilled over without the use of a condenser.AROMATIC SERIES 265 at 310-320° for about 5 minutes. 2860. after the solution of the fusion in water. and the reaction is complete. the ether. Boiling-point. The melted mass is then poured on a strong copper plate the edges of which have been turned up and of sufficient size so that the bottom is covered by a thin layer of the mass. Melting-point. 123°. Yield. and after cooling is extracted with ether. the phenol is liberated on acidifying with hydrochloric acid. besides the phenol. although not in so large quantities as the /J-naphthol. and carbon dioxide passed into it for a long time. Further.OH + CH S .O.OH + NH 3 = C 10 H 7 . for example. this is filtered off. etc. are weak acids which dissolve in water solutions of the alkalies to form salts. /S-naph* thylamine is prepared by the action of ammonia under pressure: C 10 H r . cresols. from the /2-naphthol.O. /3~Naphthol only separates out.NH 2 + H2O. Docs not take place but can only be obtained by the action of halogen alkyls on phenol salts: C6H5.OH = QH 5 . The filtrate is acidified with concentrated hydrochloric acid upon which the benzoic acid is precipitated. in that their hydroxyl groups are more capable of reaction than those of the phenols. the ethers are easily prepared: C16H7.CH S + H a O). EXPERIMENT: A mixture of £-naphthol and benzoic acid is dissolved in a diluted caustic soda solution.OH + CH 3 .266 SPECIAL PART the manufacture of azo dyes. The phenols. While. Still the acid nature is so weak that the salts can be decomposed by carbon dioxide. a-Naphthol is also prepared in the same way by fusion of a-sodiumnaphthalene sulphonate with sodium hydroxide. The naphthols differ from the phenols of the benzene series. the ether of phenol cannot be prepared from the phenol and corresponding alcohol by abstracting water: (C 6 H 5 .CH 3 + H2O. Naphthylmethyl ether . By heating the naphthols with an aliphatic alcohol and sulphuric acid.ONa 4. in consequence of the negative character of the aromatic hydrocarbon residue.ICH 3 = C 6 H 5 .CH 3 + Nal. use is frequently made of this property for the purification and separation of phenols. as such and in the form of its sulphonic acids. which also finds technical use for the manufacture of azo dyes.OH = C 10 H 7 .O. it is unnecessary to subject it to any further process of purification. the distillate is filtered.AROMATIC SERIES 267 23. the water evaporating being replaced by a fresh quantity. it is again melted by a short warming in a large flame. is distilled with steam until no more o-nitrophenol passes over. add drop by drop. a mixture of 50 grammes of crystallised phenol and 5 grammes of alcohol. REACTION: NITRATION OF A PHENOL EXAMPLE : 0. and dried in a desiccator. The oil still present in the distillation flask is boiled with a mixture of 1 part by volume of concentrated . The principal portion of the water solution is then decanted from the oil.and p-Nitrophenol Dissolve 80 grammes of sodium nitrate in 200 grammes of water by heating. Should the phenol solidify in the separating funnel. upon which the p-nitrophenol separates out in long. from a separating funnel. this is washed again with water. and the filtrate boiled for a quarter-hour with 20 grammes of animal charcoal. the water solution is filtered from the undissolved portions. In order to obtain the non-volatile p-nitrophenol remaining in the flask. After cooling. after cooling. with frequent stirring. the mixture is cooled by immersion in cold water. Concerning the removal of the o-nitrophenol solidifying in the condenser. see page 37 (temporary removal of the condenserwater). After the reaction-mixture has been allowed to stand for two hours. the reaction-product collects as a dark oil at the bottom of the vessel. pressed out on a porous plate. and after the addition of ^ litre of water. melted by warming. with frequent stirring it is treated with double its volume of water. the o-nitrophenol washed with water. the solution is treated. almost colourless needles. During this addition the temperature is kept between 25-30 0 by immersing the beaker in water. The charcoal is then filtered off and the filtrate allowed to stand in a cool place over night. To the mixture cooled to 250 contained in a beaker. with 100 grammes of concentrated sulphuric acid. Since it is obtained completely pure. with stirring. There is thus obtained a second crystallisation. EXPERIMENT: Dissolve some o-nitrophenol in a solution of sodium carbonate by warming. in contrast to the corresponding hydrocarbons. X)H o. The mon-acid phenols of the benzene series are. 114 0 . etc. 30 grammes and 5-10 grammes respectively. Upon nitrating phenol. in order to facilitate the elimination of the water.and p-nitrophenols are formed simultaneously. they are re crystallised from dilute hydrochloric acid with the use of animal charcoal. since they. filtered after partial cooling and the filtrate allowed to stand over night.and p-Nitrophenol On nitrating the homologues of phenol. OH + NOo. whereas the action of concentrated nitric acid alone upon phenol is so energetic. In order to prepare m-nitrophenol. pass. The nitrophenols behave in all respects like the phenols. 45 ° . very easily nitrated. and never the m-position. the negative character of the phenol is so strengthened that the nitrophenols not only dissolve in alkalies. the nitro-groups always enter the o. it is necessary to start from m-nitroaniline. In consequence of this action. OH = C6H4< + H 9 0. If the crystals which have separated out are still contaminated by the oil.and p-positions to the hydroxyl group. this is diazotised and its diazo-solution boiled with water. In the nitration of benzene. QY§r to &midophenols on energetic reduction. that in this case it must be diluted with water. the former of which is volatile with steam: /NO 3 C6H5. In addition the nitrophenols show the characteristics of the nitrocompotinds in general. with the addition of animal charcoal. the scarlet red sodium salt is formed. But by the entrance of the negative nitro-group. but also in the alkali carbonates. the nitrophenols cannot be precipitated from their alkaline solutions by carbon dioxide. for example. concentrated sulphuric acid must be added.268 SPECIAL PART hydrochloric acid and 2 parts by volume of water. . the o. Yield. Melting-point of p-Nitrophenol. Melting-point of o-Nitrophenol. 74) containing 50 grammes of toluene is placed in a well-lighted position. The toluene is heated to boiling and a current of dry chlorine conducted into it until its weight FIG.c. In order to be able to judge of the course of the reaction. with the toluene. the increase in weight will indicate how far the chlorinating action . best in the sunlight. REACTION: (a) CHLORINATION OP A SIDE-CHAIN OP A HYDROCARBON. the flask. is weighed before the experiment. cooling and weighing the flask. round flask with a wide neck (Fig.AROMATIC SERIES 269 2 4 . (J>) CONVERSION OF A DICHLORLDE INTO AN ALDEHYDE EXAMPLES: (a) Benzalchloride from Toluene (b) Benzaldehyde from Benzalchloride {a) A 100 c. is increased by 40 grammes*. By interrupting the passage of the chlorine from time to time. 74. (5) In order to convert the benzalchloride into benzaldehyde. The oil passing over with the steam is treated. with 500 c. 1790. when perfectly pure benzaldehyde passes over. On cooling. during which it must not be heated too long. Should crystals of the double compound o f benzaldehyde and sodium hydrogen sulphite separate out. For this purpose the apparatus necessary (cork with a glass tube) has been prepared before the heating in the oil-bath. after the evaporation of t h e ether. together with all of the liquid. and. I n summer the reaction is complete in a few hours. different products are formed. The length of the operation varies greatly. Under the preparation of brombenzene it has already been mentioned that by the action of chlorine or bromine on aromatic hydrocarbons containing aliphatic side-chains. 1210. This alkaline liquid is now subjected to distillation with steam. water is added until they are dissolved. and the filtrate treated with anhydrous sodium carbonate until it shows a strong alkaline reaction. The water solution is then filtered through a folded filter from the oil remaining undissolved. The reaction may be materially assisted by adding 4 grammes of phosphorus pentachloride to the toluene. Boiling-point. Before the crude benzaldehyde is subjected to purification. and the filtrate acidified with much concentrated hydrochloric acid. . since it is volatile with steam.2JO SPECIAL PART has proceeded. Melting-point. is distilled. of water and 150 grammes of precipitated calcium carbonate (or floated chalk or finely pulverised marble) and the mixture heated four hours in a hemispherical oil-bath to 1300 (thermometer in t h e oil). Without further heating. until after long shading the greater part of the oil has passed into solution. it is taken up with ether. the benzoic acid obtained as a by-product in the preparation of benzaldehyde separates out in lustrous leaves. the crude product thus obtained is treated in a round flask p r o vided with an effective reflux condenser. t h e liquid remaining in the distilling flask is filtered while hot through a folded filter. It is filtered off and recrystallised from hot water. during t h e cloudy days of winter a half or a whole day may be necessary. with a concentrated solution of sodium hydrogen sulphite.c. steam is passed through the h o t contents of the flask until no more oil distils over. CHC1 2 + Cl2 = C 6 H 5 . since the benzotrichloride is not changed even by passing in the chlorine for a longer time. CC13 + HCL Benzotrichloride The formation of benzotrichloride is the final result of the action of chlorine under these conditions. from time to time. and the exact point to which the introduction of chlorine should be continued in order to get a certain definite compound must be determined.5. CHC12 + HC1 Boiling Benzalchloride C 6 H 5 . the increase in weight of the substance being chlorinated is determined.5 = 112. CH2C1 + Cl2 = C6H5.5 = 7 5 and 3 x 37. chlortoluene is formed. that weighed quantities cannot be used. unlike the liquid bromine. the chlorine atom enters the side-chain: C6H5. the increase in parts by weight must be respectively 2 x 37.5). therefore in the preparation of benzylchloride. CH3 + Cl2 = CCH5. In most organic chlorinating reactions. besides the main reaction.AROMATIC SERIES 271 depending on the temperature at which the action takes place. CH3 + Cl2 = C 6 H 4 / At ordinary temperatures + HCL Chlortoluene If. and finally a third. Since the conversion of one molecule of toluene to benzylchloride requires an increase of weight equal to the atomic weight of chlorine minus the atomic weight of hydrogen (Cl — H = 34. in the above example. results in the conversion of a portion of the toluene to benzalchloride and .5 parts by weight.g.^ chlorine acts at lower temperatures on toluene. 100 parts by weight of toluene must take up an additional weight of chlorine = 37. on the other hand. a second. CH2C1 -f HCL At boiling temperature Benzylchloride If chlorine is conducted into toluene at the boiling temperature for a long time. e. hydrogen atom of the methyl group is substituted: C6H5. and correspondingly in the preparation of benzalchloride or benzotrichloride. The replacement of hydrogen by chlorine directly presents the difficulty. chlorine is conducted into boiling toluene. If. the chlorine entering the benzene ring: C 6 H 5 .This is accomplished if. a side reaction also takes place which. COONa = CH S . NH 2 + HC1 Benzylamine C 6 H 5 .CH2C1 + H2O = C 6 H 5 . C6H5 + NaCl Benzylacetate C6H5. OH + 3 HC1 Benzole acid If the halogen atom is in the ring. upon which the acid acts with the liberation of carbon dioxide. in cases 1 and 2.272 SPECIAL PART benzotrichloride. Concerning their chemical properties. in accordance with the following equations: (1) C6H5. Care is taken therefore in the above preparation not to expose the face to the vapours. CH 2 . This is usually accomplished by the addition of a carbonate. in part colourless crystallisable solids. in that their vapours violently attack the mucous membrane of the eyes and nose. CH 2 . they decompose. while another portion is only chlorinated to benzy\ chloride.— the aromatic alcohols.CHO + 2 HC1 Benzaldehyde (3) C6H5. the hydrochloric acid formed in the reaction acts in the opposite way and may regenerate the original chloride. and acids. But since. CO. CH2C1 + KCN = C 6 H 5 . and further to prevent the chlorination products from coming in contact with the hands. Accordingly the reaction-product obtained above consists essentially of benzalchloride mixed with a small quantity of benzyl chloride and benzotrichloride.OH + HC1 Benzyl alcohol (2) C6H5. The halogen derivatives of the aromatic hydrocarbons containing the halogen in the side-chain are in part liquids. these two isomeric series differ in that the compounds containing the halogen in the side-chain are far more active than those in which the halogen occurs in the benzene ring. which are distinguished from their isomers containing the halogen in the benzene ring.CHC12 + H2O = C 6 H 5 . as is apparent from the following equations: C6H5. aldehydes. CHX1 + NH 3 = C 6 H 5 . CN + KC1 Benzyl cyanide The chlorides obtained by substituting a side-chain are of importance for making certain preparations. CO. OCH 2 . none of these transformations will take place. CH2CI + CH 3 . CC13 + 2 H2O = C6H5.CH 2 . it must be neutralised. On boiling with water. . the chlorides. the aldehyde dissolves. while the calcium benzoate remains in the distillation flask. the chlorination product obtained consists essentially of benzalchloride. while the impurities remain undissolved. If the reaction-mixture is distilled with steam. C 6 H 5 . with the addition of calcium carbonate. mixed with small amounts of benzylchloride and benzotrichloride. benzyl alcohol is first formed. yielding primary alcohols on reduction and carbonic acids on oxidation. crystals of benzoic acid appear. benzaldehyde may also be prepared directly by boiling it with water in the presence of lead nitrate or copper nitrate. In order to separate the benzaldehyde from benzyl alcohol. If the distillate is shaken with a solution of sodium hydrogen sulphite. in part solids. the cheap calcium carbonate (marble dust) is used.CHO + O = C 6 H 5 . From the benzylchloride. If the mixture is boiled with water.OH. and the above method for the preparation of benzaldehyde is. an imitation of the technical process used for obtaining the substance. a mixture consisting mainly of benzaldehyde. and the sulphite compound of the aldehyde decomposed with sodium carbonate. That they unite with acid sulphites to form crystalline compounds has been mentioned: . A large proportion of the so-called "benzoic acid from toluene" is obtained in this way as a by-product in the technical preparation of benzaldehyde. benzyl alcohol. As above mentioned. possessing a pleasant aromatic odour. the free benzoic acid may be obtained as above. and a small amount of chlorides which have not taken part in the reaction. These are filtered off. which is oxidised by the nitrate to benzaldehyde. pass over with the steam. the pure aldehyde passes over. They show the characteristic aldehyde reactions. After a long time. advantage is taken of the general property of aldehydes of uniting with acid sodium sulphite to form soluble double compounds. EXPERIMENT: A few drops of benzaldehyde are allowed to stand in a watch-glass in the air. on a second distillation with steam. benzaldehyde. and other impurities.AROMATIC SERIES 273 In practice. as far as possible. By acidifying the residue. The aromatic aldehydes are in part liquids. besides benzylchloride and benzoic acid — the latter being converted into the calcium salt by the carbonate — is obtained.CO. From benzylchloride. as mentioned under acetaldehyde. NH 2 = C 0 H. the mixture is then allowed to stand over night. C(JH. of benzaldehyde and i c. Benzaldehyde is prepared technically on the large scale.CH=N . Its most important application is for the manufacture of the dyes of the Malachite Green series. and not a glass stopper. drops of water separate out. = 2 H2O + | N C 6 H 3 . and shake. CH N . of benzaldehyde add a concentrated solution of sodium hydrogen sulphite. CHO + CCH«. of pure aniline.274 SPECIAL PART yOH C6H5. . with hydroxylamine and phenyl hydrazine.. To the crys1 B. REACTION: SIMULTANEOUS OXIDATION AND REDUCTION OF AN ALDEHYDE UNDER THE INFLUENCE OP CONCENTRATED POTASSIUM HYDROXIDE EXAMPLE: Benzoic Acid and Benzyl Alcohol from Benzaldehyde 1 Treat 20 grammes of benzaldehyde in a stoppered cylinder or a thick-walled vessel with a cold solution of 18 grammes of potassium hydroxide in 12 grammes of water. CHO + HSO3Na = C0H5.. according to the experiment conditions. CH \SO. and shake until a permanent emulsion is formed. Further.CHz=N Benzalazinc Aldehydes also condense readily with primary aromatic bases with the elimination of water: C6H5. to form oximes and hydnizones.c. CH [ O + H j N . the aldehydes react. With hydrazine they yield. NH* Henzalhydrazinc ]N C u H a . + H a O Benzylidcncaniline EXPERIMENT : In a test-tt^e make a mixture of i c. since at times a glass stopper becomes so firmly fastened that it can be removed only with great difficulty.NH 2 = HaO + C n H 5 . * 25. the not very stable hydrazines or the more stable and characteristic azines: C 6 H 5 . crystals of benzylideneaniline being formed.Na EXPERIMENT: T O £ e x .c. CHzrN . On cooling. and of cinnamic acid (see these preparations). and warm gently. 2394. The vessel is closed by a cork. An additional number of characteristic aldehyde reactions will be taken up later in practice. 14. and the mixture solidifies. T h e mixture solidifies after a short time to a crystalline mass. CflH5 Accticbcnzyl ester .CH/ / R Bcnxyl ether V> CH CH/ Bcnxylmcthyl other CH8. CO. the different primary alcohols may be prepared advantageously by this reaction. one aldehyde molecule being oxidised to the corresponding acid.g. L—-LHO Furfuntl Furfurane alcohol Pyxomucic acid The primary aromatic alcohols behave in all respects like the corresponding aliphatic alcohols in forming ethers and esters. /OCH 3 X8Hr anisic alcohol p-Cf 1/ and cufninic alcohol p-QH4<f ' \CH. respectively. benzyl alcohol passes over at 2060. After the evaporation of the ether the residue is subjected to distillation. wiih alcoholic potash at the ordinary temperature or on.OH are obtained by treating anisic aldehyde and cuminol.. with higher molecular weights. The aldehyde of furfurane. the so-called aldehyde resins. e. Thus. L.0. The beny. and the other being reduced to a primary alcohol: 2C/(1U.AROMATIC SERIES 275 talline paste (potassium benzoate) separating out. about-8 grammes. heating. two molecules are decomposed by one molecule of potassium hydroxide.. acid is precipitated from the alkaline solution on acidifying with hydrochloric acid.oir.OCHa. water is added until a clear solution is obtained from which the benzyl alcohol is extracted by repeatedly shaking with ether. OH.CO..: 'SO C 8 II R . furfurol. is converted under the same conditions into furfurane alcohol and pyromucic acid: IK" CH + HJJO = C4HHO. While many aliphatic aldehydes (see acetaldehyde) are converted by alkalies into more complex compounds.OH \OHL. Yield.CHO Since the aldehydes are in part easily obtained. the aromatic aldehydes under similar conditions react smoothly. m-Nitrobenzylateohol may also be obtained easily from m-nitrobenzaldehydc and aqueous potash. CH tf . OH + C 4 H. 276 SPECIAL PART On oxidation they are converted first into aldehydes and finally into acids: C6H5. 26. OH + O2 = C6H5. In the first phase. Boil on the water-bath for one hour (reflux condenser). washed with alcohol. Yield. OH 4. 1340. 198. For conversion into benzil (see next preparation). CH 2 . REACTION: CONDENSATION OF AN ALDEHYDE BY POTASSIUM CYANIDE TO A BENZOIN EXAMPLE : Benzoin from Benzaldehyde 1 Mix 10 grammes of benzaldehyde with 20 grammes of alcohol and treat the mixture with a solution of 2 grammes of potassium cyanide and 5 c. about 90% of the theory. Melting-point. substances are obtained which possess the same composition. iPotsLssium The hydrocyanic acid then reacts with a second molecule of alde*A. CHO + H2O? C6H5. COOH + H2O. but with double the molecular weight of the aldehyde: C 6 H 5 . one molecule of aldehyde reacts with one molecule of potassium cyanide: (1) C c H 5 . OH Since a small quantity of potassium cyanide has the power to condense large quantities of the aldehyde.c. In order to obtain perfectly pure benzoin. . The hot solution is poured into a beaker and allowed to cool slowly. If an aromatic aldehyde of the type of benzaldehyde is wanned in alcohol solution with potassium cyanide. they need not be recrystallised.CHO= I .CH—C 6 H 5 2C 6 H 5 . the reaction may possibly take place as indicated by the equations below. of water. and dried on the water-bath. CH 2 .150.COK + HCN.CO|H-f CN|K = C 6 H 5 .CO.O = C6H5i. the crystals separating out are filtered off. a small portion of the crude product is recrystallised from a little alcohol in a test-tube. in the second phase: (2) C 6 H 5 . C 6 H 4 . C 3 H 7 • 2p-C6H4< I X:HO Cuminol OH Cuminoin With potassium cyanide furfurol yields furoi'n: 2C 4 H 3 O.CO. CgH 4 . CH.CHO= Furfurol C 4 H 3 O.C6H5. CH. CH. mandelic nitrile. OH OH The molecule of potassium cyanide required for equation (i) is thus again formed. and may condense two more molecules of aldehyde. CO. C6H4.AROMATIC SERIES 277 hyde. OCH3 :HO Anisic aldehyde OH Anisoin yC 3 H 7 = C3H7. like secondary alcohols if the group CH.C 4 H 3 O I OH Furoin Benzoin and its analogues are derivatives of the hydrocarbon dibenzyl. and in fact benzoin on reduction with hydriodic acid is converted into this hydrocarbon. the ketone group is converted into the secondary alcohol group • . C6H5. forming an addition-product. CH—CgH 4 . The benzoins act. C6H5 | = | +KCN. In the same way from anisic aldehyde and cuminol. CH2 . If benzoin is reduced with sodium amalgam. CH 2 .CH.COK+ C6H5. Thus they have the power to form oximes and hydrazones with hydroxylamine and phenyl hydrazine respectively. CN C6H5. on the one hand. on the other hand. and the formation of the benzoin: (3) C 6 H 5 . respectively: / ) C H 3 = CH 3 O. and. CO.CHO + H C N = I OH Mandelic nitrile In the third phase a molecule of potassium benzaldehyde acts upon a molecule of the nitrile with the elimination of potassium cyanide. like ketones if the carbonyl group (CO) takes' part in the reaction. OH (the secondary alcohol group) reacts. etc. there are obtained anisoin and cuminoin. C O . . Dibenzoyl=BenzQ The next preparation will deal with this reaction. CO. with the sodium compound the same kind of syntheses may be effected as with acetacetic ester: C6H5. CH. one of the two hydrogen atoms of the methylene group (CH 2 ).C6H. as in acetacetic ester. CH. further. C6H5 C 6 H 5 . with frequent shaking. CH—C6H5 I + IC«H* = I +NaI.CH2. CO . CH. Na C2H5 Sodium desoxybenzoin Etbyl desoxybenzoin Benzoin. C6H5 I + H2 = | | OH OH OH Hydrobenzom If the reduction is effected by zinc and hydrochloric acid or glacial acetic acid. + H2O.CH. the reaction-mixture is poured into cold water. with twice its weight of pure concentrated nitric acid. When the oxidation is. the carbonyl group is not attacked. the hydroxyl group being capable of reacting with alkyl. C6H5 C6H5.C 6 H 5 + O A.ended. but the alcohol group is reduced and desoxybenzoin is obtained: C6H5. because in it.H 2 = OJJ Desoxybenzoin a compound of especial interest.and acid-radicals to form ethers and esters.CO. acts as an alcohol. I 4. REACTION: OXIDATION OF A BENZOIN TO A BENZIL EXAMPLE : Benzil from Benzoin The crude benzoin obtained in the preceding preparation is finely pulverised after drying. as is the case with all secondary alcohols : C 6 H 5 . CO. the alcohol group is oxidized to a ketone group.C H . C H .278 SPECIAL PART C 6 H 5 . 27. and heated in an open flask. C6H5 C6H5. = C d H 5 . may be replaced by sodium. CO. for i|—2 hours on a rapidly boiling water-bath.C 6 H 6 +H 2 O.CO.CO. If oxidizing agents act on benzoin. in consequence of the acidifying influence of the adjoining negative carbonyl and phenyl groups.CO. CO.C 6 H 5 + H 2 O= C e H^ QH/I OH Diphenylglycolic acid = Benzilic acid >C-CO. 14.CO. anisilic a n d cuminilic acids. CO. Benzil forms two monoximes and three dioximes.OH. C6H4. benzil undergoes a remarkable change. in a similar way. Anisil and cuminil also yield. compounds of the benzil series. C 8 H r Anisil Cuminil Benzil acts like a ketone in that it forms oximes with hydroxylamine.CO. C6H4.AROMATIC SERIES 279 after the mass solidifies the nitric acid is poured off. The analogues of benzoin also give. Yield. The constitution of these compounds will be discussed later. CO. it is then washed several times with water. The equation representing the oxidation of benzoin to benzil has been given under the preceding preparation. or an equivalent amount of the purest salt 1 B . on oxidation. Thus from anisoi'n and cuminoiin. The oximes are of exceptional interest. about 90% of the theory. 28. CO. After filtering off the crystals separating out. since our knowledge of the stereochemistry of nitrogen proceeds from them.OCH3. anisil and cuminil respectively are obtained: CH3O. 95 0 .235 . Melting-point. they are dried in the air on several layers of filter-paper. under the preparation of benzophenone-oximeOn fusion with potassium hydroxide or by long heating with a water solution of potassium hydroxide. pressed out on a porous plate. C3H7. and crystallised from alcohol. C6H4. in that by taking up water it passes over to the so-called benzilic acid: C 6 H 5 . REACTION: THE ADDITION OF HYDROCYANIC ACID TO AN ALDEHYDE E X A M P L E : Mandelic Acid from Benzaldehyde 1 (a) Mandelic "Nitrile In a flask containing 13 grammes of finely pulverised 100% potassium cyanide. C6H4. with frequent shaking. The reaction-mixture is then allowed to stand over night in a cool place. then poured into about 5 volumes of water. the crystals separating out. very easily on stirring. and finally separated in a dropping funnel. the flask being cooled with ice. The reaction-mixture is then allowed to stand. and then washed with not too much water. almost quantitative.90.C—OH solidifies to a pasty mass. The double compound is stirred up with water to a thick paste. with frequent shaking. and the nitrile appears as an oil. of a concentrated solution of sodium bisulphite over 15 grammes of benzaldehyde in a beaker. Owing to the ease with which the nitriles decompose. (b) Saponification of the Nitrile The nitrile is mixed with four times its volume of concentrated hydrochloric acid in a porcelain dish. stir the mixture / H with a glass rod until the addition product C6H5.c. z. and washed once with a little water. Yield. a further purification is not possible. are triturated with a little water. and add to this from a separating funnel. pressed firmly together. pour 20 grammes of freshly distilled benzaldehyde. . and evaporated on the water-bath until crystals begin to separate out on the upper surface of the liquid. the crystals go into solution. A further quantity of the acid may be obtained by 1 Ch. and treated with a cold solution of 12 grammes potassium cyanide in 25 grammes of water. which is separated from the solution in a dropping funnel. the oil washed with water several times.28O SPECIAL PART available. 1896. Much better results are obtained by preparing mandelic nitrile1 thus : Pour 50 c. for one hour. drop by drop. After a short time. a quantity of the most concentrated hydrochloric acid. It is then filtered with suction. corresponding to 7 grammes of anhydrous hydrochloric acid (about 20 grammes concentrated acid). filtered off with suction. which precipitates the chinchonine. and are not washed. a purer salt will crystallise out. using for each gramme of the dried salt 25 c. The filtrate. after evaporating off the ether. In order to purify the crude d-cinchonine mandelate separating out. the residue is heated in a watch-crystal some time on a waterbath. which contains dextro-ammonium mandelate. and 500 c.1773. in winter in a cellar if necessary).c. after recrystallisation from diluted alcohol.c. 2385. n 8 ° . then. If the solution be seeded with a few crystals of d-cinchonine mandelate and allowed to stand under the same conditions referred to above. 32. On filtering the cold solution the undissolved portions remaining are not washed. The crude mandelic acid is pressed. on cooling. pressed out on a porous plate. this is filtered off. and recrystallised from water. crystals of dextro-mandelic acid 1 B . To obtain the free dextro-mandelic acid the purified salt is dissolved in not too much water. the portions undissolved are filtered off. Yield. out on a porous plate. in summer in a refrigerator. and allow it to stand. and. is acidified with hydrochloric acid and extracted with ether. 10 grammes of crystallised mandelic acid. Meltingpoint. and is obtained pure by recrystallising it from benzene. of water is heated with quite frequent shaking in an open flask for an hour on an actively boiling water-bath. may be used for other experiments. (c) Separation of the Inactive Mandelic Acid into its Active Co?npone?its1 A mixture of 20 grammes of crystallised cinchonine. . one or more days in a cool place (6-8°. in an open flask upon a water-bath). After cooling. If the residue obtained on evaporating the ether be heated in a watch-glass some time on a water-bath. To this clear solution (a) add a few crystals of d-cinchonine mandelate (see below). about 10-15 grammes. with quite frequent shaking. it is filtered off (filtrate A). according to the conditions. of water (heating as above described for an hour. 16. and then treated with a slight excess of ammonia.AROMATIC SERIES 281 extracting the filtrate with ether. OH >C< C2H/ \CN Diethylglycolic nitrile C6H5. The pure lsevo-mandelic cannot be obtained readily from small quantities of mandelic acid. •From the three preparations thus obtained. and their properties investigated by a polariscope (consult text-books on Physics). viz. they are pressed out on a porous plate and recrystallised from benzene. and the impure 1-acid. it should be laevo-rotatory. a saturated solution of salt until a slight precipitation takes place. The crystals thus obtained are those of cinchonine hydrochloride upon which small quantities of d-cinchonine mandelate have been deposited. CH< N:N Aldehydecyanhydrine a-lactic nitrilc QH 5 . but a preparation showing to a slight extent lsevo-rotatory power may be obtained in the following way : The filtrate A is worked up for the free acid exactly as in the method described for pure dextro-cinchonine mandelate. and is allowed to stand until crystals separate out. the pure d-acid.es with the formation of a-oxyacid nitriles: /OH CH 3 . CHO + HCN = CH 3 . 133-1340. drop by drop. to cause a further separating out of the d-salt. If one is not in possession of d-cinchonine mandelate for the first experiment. since a portion of the d-modification has been removed from the solution. water solutions of the proper concentration are prepared. inactive mandelic acid. a proper seeding material is prepared as follows : To a few cubic centimetres of solution (a) obtained above is added. however. the latter are in sufficient quantity. CO. Hydrocyanic acid unites with aromatic as well as aliphatic aldehydes and keton.282 SPECIAL PART separate out. The solution is now heated until the precipitate redissolves. Melting-point. which may require several days. CH< X:N Mandelic nitrilc . CHO + HCN Bcuzaldebyde /OH = CCH5. C2H5 + HCN = Diethylkctone CH ' . OC2H5 Acctacetic ester y/\. If hydro- . Thus in the sugar group the cyanhydrine reaction is of extreme importance.: >OH C6H5. CO.CO. it is frequently used for the preparation of a-oxyacids.OH Mandelic nitrile Mandelic acid Since the cyanhydrine reaction takes place smoothly in most cases. but also for the syntheses of sugars or sugar-like substances containing long chains of carbon atoms. e.CO.C—CO. CH3 + HCN = Acetophenone 283 C6H5v /OH V<" Acetophenonccyanhydrine This reaction also takes place with more complex compounds containing the carbonyl group: CH 3 .OH X)H C6H3. C—CH2. by boiling with hydrochloric acid. CH< 4. CH + KNaSO s SO. CH 2 . OH CN a-Cyan-a-lactic acid C6H5. CH< /OH + 2 H2O + HC1 = C6H6. OC2H5 + HCN = CH 3 .OH + HCN Pyroracemic acid = CH3. In reference to the latter. the free oxyacid is obtained. CO.AROMATIC SERIES C 6 H 5 . one example may be mentioned. OH + HCN Benzoylcarbinol = C 6 H 5 . CH 2 .g. CH = C6H6. not only for its value in determining constitution. CO . OH CN The reaction may be effected by digestion with already prepared hydrocyanic acid at ordinary or higher temperatures.NH4C1 \CN \CO. for example. CO. — treating the aldehyde with sodium bisulphite. If the second method be followed. OH CN CH3. C—CH2.Na+K|CN If the oxynitriles are subjected to saponification.OH y/\. CO. — the reaction takes jface in accordance with the following equation: . OH / \ . but in most cases it is more advantageous to employ nascent hydrocyanic acid as above. and owing to their power of revolving the plane of polarisation. Mandelic acid belongs to the class of substances containing an asymmetric carbon atom. para-mandelic acid. which. I CH2. With the aid of certain micro-organisms. and so on. so-called. If. an equal number of molecules of the dextro. which on saponification yields an oxyacid. while another organism.. the active acids can be obtained from the inactive modifications. is reduced. there is first obtained an oxynitrile.OH I (CH.e. e.and laevovarieties are always obtained. it exists in two different space modifications. or rather the inner anhydride (lactone) into which it easily passes. <?•£". it destroys the laevo-modification.OH saponified-*.OH)4+ HCN= I I CH. and leaves the other.OH Aldoheptose With the substance thus obtained a similar reaction may be carried out. the wellknown Penhillinm glaucum is allowed to grow in a solution of ammonium para-mandelate. By treatment with acids. the inactive compounds may be decomposed into their active constituents. the cinchonine salt of para-mandelic acid is allowed to crystallise.OH CHO I I CHO I CH.OH reduced->-(CH. i. Saeckaromycts ei/zpsoideus. If. the free active acids may be obtained. which is an aldehyde. If this. . since. in the synthesis of compounds with an asymmetric carbon atom from inactive substances. unite to form the inactive.OH (CH.OH) 4 I CH 2 .OH) 5 I CH 2 . are called dextro.g.. later. OH Like all compounds of this class. But. and there is thus obtained a sugar containing one more secondary alcohol (CHOH) group than the original grape sugar: CN CO.and laevo-mandelic acids.. which bear the same relation to each other as does an object and its image. one which is in combination with four different substituents: SOH XX).OH CH. the carboxyl group is reduced to an aldehyde group. the more difficultly soluble salt of the dextro-acid separates out first. by different methods. the lsevo-salt crystallises. consumes the dextro-modification..| (CH. The acid obtained in the above synthesis is optically inactive.284 SPECIAL PART cyanic acid is united with grape sugar. and then.OH). in the above case. AROMATIC SERIES 285 29. forming sodium phenyl lactate: C 6 H s . Melting-point. on cooling. and filtered.CH. 16. 133 0 . both freshly distilled.CO.CH 2 . The solution is then boiled a short time. Sodium cinnamate The reaction. . After the reaction is complete. but it proceeds in two phases. In the first. 789. REACTION: PERKIN'S SYNTHESIS OP CINNAMIC ACID* EXAMPLE : Cinnamic Acid from Benzaldenyde and Acetic Acid A mixture of 20 grammes of benzaldehyde. and 10 grammes of anhydrous pulverised sodium acetate (for the preparation. 30 grammes of acetic anhydride. the hot reaction-product is poured into a large flask. it is recrystallised from hot water. the sodium acetate unites with the aldehyde. as appears from the equation. and then distil with steam.48. by the direct union of the aldehyde-oxygen atom with the hydrogen atoms of the methyl group and a combination of the resulting residues. the cinnamic acid separates out in lustrous leaves. B. 227. Yield. CO. add water.CO. 10. ONa + H 2 O. with some animal charcoal.ONa. about 15 grammes. Should it not possess the correct melting-point. 68. long. a calcium chloride tube is placed in the upper end of the condenser over night. The quantity of water used here is large enough so that all of the cinnamic acid dissolves except a small portion of an oily impurity. in an oil-bath at 1800. If the experiment cannot be completed in one day. CH=CH. until no more benzaldehyde passes over. 1877.ONa= | OH Sodium phenyl lactate 1 J . is heated in a flask provided with a wide vertical air-condenser about 60 cm. however. CO. for 8 hours. CHO + CH S . (1) C 6 H 5 . A. does not take place. ONa = C6H5. see page 127).CHO + CH 3 . The reaction involved in the Perkin synthesis takes place in accordance with this equation: C6H5. 1436. Halogen substituted aliphatic acids will also react . is proved by the following facts: If. and therefore. the anhydride reacts with the aldehyde. at higher temperatures the sodium salt of proprionic acid and acetic anhydride decompose into sodium acetate and proprionic anhydride. OH = C 6 H 5 . condenses with the benzaldehyde. its nitro. C H . eg.ONa + I OH That sodium acetate. +C 6 H 5 .CH=CH. since in place of benzaldehyde. the homologues of sodium acetate may be used as has been pointed out. under the influence of acetic anhydride. loses water.CO. thus from benzaldehyde and chloracetic acid.CH.CO. chlorcinnamic acid is obtained: C 6 H 5 . so that cinnamic acid is obtained.CO. but only at the heat of the water-bath. this salt.CO. CO. apparently.ONa It follows from this that the sodium salt used always takes part in the reaction.OH = | 6 . ONa + H2O.CHO + CH 3 . and this is heated with benzaldehyde and acetic anhydride. CHO + C H r Cl .CO. but methyl cinnamic acid: C6H5.ONa= | | OH CH3 (2) C6HS.CH=C—CO. On the other hand. its homologues. instead of sodium acetate. In place of the aliphatic homologues of acetic acid the aromatic substituted acetic acids can also be used. sodium proprionate is used. etc.286 SPECIAL PART In the second phase.: C 6 H 5 . The Perkin reaction is capable of numerous modifications. OH + H 2 O. CHziC—CO. CH—CH—CO. ONa C6H5. Phenyl acetic acid Phenyl cinnamic acid .CH 3 . upon which the sodium cinnamate is formed: = C 6 H 5 .C H . CH=CC1. The condensation in these cases always takes place at the carbon atom adjoining the carboxyl group.OH. In the experiment it is of course necessary that the fusion is not carried out at so high a temperature as in the above example. CO. cinnamic acid is not obtained. OH CH3 CH8 Sodium methyl cinnamate (2) C 6 H 5 .CHo. and not the acetic anhydride.. may be used.CH 2 . ONa (1) C 6 H 5 .and oxy-derivatives. CHziCH. CH—CHC1. CO. Hypochlorous acid also unites with cinnamic acid with the formation of phenylchlorlactic acid: C6H5.CHBr. CHzuCH. CHC12 + CH 3 . Dibromhydrocinnamic acid Further. CO . an ester of it. CO. CO. or better. CHzuCH. is nitrated. By the action of nascent hydrogen two atoms of hydrogen are added to the molecule of cinnamic acid with a change from'double to single union: C6H5. OH + HBr = C6H5. since they form salts. CO. CO.g. CO. OH Dichlorhydrocinnamic acid C 6 H 5 . a mixture of the o. instead of benzaldehyde: C6H5. CO. etc. behave on the one hand like acids. Cinnamic acid.AROMATIC SERIES 287 These examples are sufficient to show the wide application of the Perkin reaction. OH . CHzzCH. OH + H a = C 6 H 5 . Hydrocinnamic acid It also combines with chlorine and bromine:' C6H5. CO . e. OH. OH. OH + C1OH = | OH The o-nitrocinnamic acid from which indigo is synthetically prepared is of technical importance. C 6 H 5 . ONa = C e H 5 .: Q H 5 . chlorides. its homologues and analogues.CH=CH . and hydriodic acids. amides. Further. esters. they show the properties of the ethylene series in that they take up by addition the most various kinds of atoms and groups. ONa + 2HCI. it unites with hydrochloric. CHBr. OH. CHC1. OH 4. CH 2 . C H = C H . OH. If cinnamic acid. If bromine is allowed to act on the o-nitrocinnamic acid. A very similar reaction takes place on heating sodium acetate with the cheaper benzalchloride. CO. CO. CO. /3-bromhydrocinnamic acid The halogen atom in these cases always unites with the carbon atom not adjoining the carboxyl group. CH 2 . CHC1.CHBr. CO . CH 2 . there is obtained: HBr—CHBr.Br2 = C 6 H 5 .and p-nitroderivatives is obtained which can be separated into its constituents. hydrobromic. OH + Cls = CeH5. and is used in indigo printing: :^C. REACTION: ADDITION OF HYDROGEN TO A S ETHYLENE JT DERIVATIVE EXAMPLE : Hydrocinnamic Acid from Cinnamic Acid In a glass-stoppered cylinder.CO. The equation for the reaction has been given under cinnamic acid. treat 10 grammes of cinnamic acid with 75 c. a stereoisomeric cinnamic acid (allocinnamic acid) is obtained. . Yield. it solidifies to a crystalline mass. and o-nitrophenylpropriolic acid is formed. in which case proceed according to the directions given on page 8. 8-9 grammes.CO. on the water-bath for a short time. The liquid is then decanted from the mercury and acidified with hydrochloric acid.C. the acid is recrystallised from water. It is then treated gradually with^bout 200 grammes of 2 % sodium amalgam. and heated gently. which bears the same relation to cinnamic acid that maleic acid does to fumaric acid: C 6 H 5 . of water. Melting-point. two molecules of hydrobromic acid are split off as in the preparation of acetylene from ethyl* ene bromide. or a thick-walled preparation glass. too much caustic soda has been used. with alkaline reducing agents. it may separate out as an oil on cooling.OH.CH H. Since it possesses a low meltingpoint.CH. which. By the decomposition of an alkaloid found with cocaine.288 SPECIAL PART If this acid is boiled with alcoholic potash. The same reaction also takes place on heating with hydriodic acid and red pbosDhorus. when cooled with ice-water and rubbed with a glass rod. The acid does not show any noteworthy reactions. 47 0 .c. as soon as this has become liquid. Cinnamic acid Allocinnamic acid 30.OC. add a very dilute solution of caustic soda until the acid passes into solution and the liquid is just alkaline.OH HO. yields indigo. After pressing it out on a porous plate.C. upon which the hydrocinnamic acid separates out as an oil . If a precipitate of sodium cinnamate separates out at this point.H C6HS. In other respects. observing the directions given on pages 24 and 25. 90 % of the theory.c. Boiling-point of benzoyl chloride. the completely liquid mixture is twice fractionated (under the hood) with the use of an air condenser. only it is possible to prepare aromatic amides by a different method from that used for the preparation of acetamide. after a short time. While acetyl chloride. (Investigations concerning the Radical of Benzole Acid.AROMATIC SERIES 289 31. 22. After standing a short time. under these conditions. of benzoyl chloride with 5 c. of water and shake. upon which. REACTION: PREPARATION OP AN AROMATIC ACID-CHLORIDE FROM THE ACID AND PHOSPHORUS PENTACHLORIDE EXAMPLE : Benzoyl Chloride from Benzoic Acid1 Treat 50 grammes of benzoic acid in a dry ^--litre flask. It is then warmed somewhat. Nr. Ostwald's Klassiker der exakten Wissenschaften. from cracking. but on a wooden block or straw ring. In order to prevent the vessel. which has become strongly heated by the reaction. EXPERIMENT : In a porcelain dish. OH + PCla = C6H5. EXPERIMENT : Treat \ c. 10 grammes of finely pulverised ammonium carbonate are treated with 5 grammes of benzoyl A.c. the benzoyl chloride is scarcely changed. 262. for the preparation of the aromatic acid-chlorides. The formation of benzoyl chloride takes place in accordance with the following reaction: C e H s . Yield. decomposes violently. benzoyl chloride is a wholly normal acid-chloride.) U 1 . with 90 grammes of finely pulverised phosphorus pentachloride under the hood. 2000. it is not placed on the cold stone floor of the hood. 3. the two are shaken well together. Benzoyl chloride differs from acetyl chloride in that it is more difficultly decomposed by water. CO. by W6hler and Liebig. Cl + POC13 + HC1 It has been mentioned under acetyl chloride that. and what was said under acetyl chloride is applicable to this chloride. phosphorus pentachloride is generally used. It must be subjected to a longer heating before all the oil has been decomposed. and the mass becomes liquid. CO. reaction takes place with energetic evolution of hydrochloric acid. acid-chlorides react with alcohols. Melting-point of benzamide. pressed out on a porous plate. the oil separating out solidifies to colourless crystals.290 SPECIAL PART chloride. 23. make the solution alkaline with a solution of caustic soda and.c. and not. NH 2 + HC1 Since the aromatic amides are generally insoluble in water.. 68-69 0 . amido-. If the reaction-mixture is cooled by water and then shaken and the sides of the tube nibbed with a glass rod. 2744. washed with water. and crystallised from water. by heating the ammonium salt of the acid. they are usually prepared by the method just given. or imido-group. 21. of water in a test-tube and add £ c. 3218. 32. OR HYDROXYL-GROUP EXAMPLE : Benzoicphenyl Ester from Phenol and Benzoylchloride1 Dissolve a small quantity of crystallised phenol (about £ gramme) in 5 c. which in the absence of alkalies is not possible: B. the chlorine atom uniting with the hydrogen of the hydroxyl-. washed with water. Melting-point. 2545. filtered with suction. primary and secondary amines. As already mentioned under acetyl chloride. The value of the SchottenBaumann reaction depends on the fact that this reaction is so essentially facilitated by the presence of sodium hydroxide or potassium hydroxide. with shaking. CtiH. and recrystallised in a small test-tube from a little alcohol. that even in the presence of water the decomposition takes place. which are filtered off with suction. . of benzoyl chloride. CO. 128°. IMIDO-. with the elimination of hydrochloric acid. they are intimately mixed with a glass rod and heated on the water-bath until the odour of the acid-chloride has vanished. CO. 17. Cl + NH3 = Q H 5 . as in the case of acetamide. heat gently a short time over a free flame. while the residues combine to form an ester or a substituted amide. 3962. The mixture is then diluted with water. 19. phenols. REACTION: THE SCHOTTEN-BAtTMANN REACTION FOR THE RECOGNITION OF COMPOUNDS CONTAINING THE AMTPO-.c. . which act in a similar way. \NH2 \NH. Cl = C6H4< + 2 HC1 \OH \O.CO.) The soluble amido-phenols. which can be recognised by its melting-point.OC. Thus. C . or of the various sugars.. At times the reaction takes place better by using potassium hydroxide in place of sodium hydroxide. only in this case acetic anhydride and not the easily decomposed acetyl chloride is used.. which is generally insoluble in. CO. (Try the experiment. other chlorides.C6H5 yNH. di.AROMATIC SERIES 291 The reaction is of great importance. it is not difficult to convert aniline (one drop dissolved in water) by the above method to benzanilide. The benzoyl derivatives are particularly well adapted to this purpose.g. glycerol. Acetyl derivatives may also be prepared in the presence of alkalies in water solution. 1630. a benzoate is formed.CO.and poly-amines are also converted into difficultly soluble benzoyl derivatives: /NH2 /NH. For the recognition of primary and secondary amines the method of procedure is the same. Cl = C 6 H / + 2 HC1. A few examples may render this statement clearer: If a water solution of a poly-acid aliphatic alcohol.CO. especially for the recognition and characterisation of soluble compounds containing the groups mentioned above. is treated with benzoyl chloride and alkali. It is obvious that if it is desired to test even small quantities of those compounds. e.C 6 H 5 In place of benzoyl chloride. and which can be recognised by its melting-point. the most difficultly soluble acid derivatives of them must be prepared. eg. or benzenesulphon chloride.C 6 H 5 6H4\ + 2 C 6 H 5 • CO. /NH.C 6 H 5 C6H4<( + 2 C6HS. from which the dissolved substance will only separate with difficulty.g. phenylacetyl chloride. can be used. water. e. and the water added to the main quantity. and the residue distilled from a fractionating flask.c.5 grammes of caustic potash in 6 grammes of water. any un1 A. After drying with calcium chloride.c. with a reflux condenser. treated with a cold solution of 1. The residue remaining in the flask is. steam is passed into it for about a quarter-hour. of concentrated hydrochloric acid. the ethereal solution washed several times with water. and 3. Boiling-point. Yield. [6] 1. and the residue. Melting-point. filtered. after cooling.c.c. and heated on a gently boiling water-bath until only small amounts of hydrochloric acid are evolved : this will require about 2-3 hours. of water. if necessary. The residue adhering to the walls of the first flask is treated with water. 30 grammes of freshly prepared and finely pulverised aluminium chloride. and 100 c. After the reaction-mixture has been treated with 10 c.ch. Benzene and Aluminium Chloride (a) To a mixture of 30 grammes of benzene. the mixture is heated two hours on the water-bath. . with cooling. about 30 grammes. 480. 30 grammes of benzoyl chloride.292 SPECIAL PART 33. with frequent shaking. of water. extracted with ether. 518. which is weighed in a dry test-tube closed by a cork. (=130 grammes) of carbon disulphide in a dry flask. of alcohol is. of water and small pieces of ice. add. 29 70. the side-tube of which is as near as possible to the bulb. and filter off. in the course of about 10 minutes. and shaken up with dilute caustic soda solution. while still wrarm. the ether is evaporated.c.5 grammes of hydroxylamine hydrochloride in 5 c. Then add 50 c.c. REACTION: {a) FRIEDEL AND CRAFTS' KETONE SYNTHESIS* (3) PREPARATION OF AN OXIME (c) BECKMANN'S TRANSFORMATION OF AN OXIME EXAMPLE : Benzophenone from Benzoylchloride. The carbon disulphide is then distilled off. is carefully poured into a large flask containing 300 c. The flask is then connected with a long reflux condenser. (6) A solution of 2 grammes of benzophenone in 15 c. CO. is treated with water. and gradually treated with 1^. Cl = C e H 5 . Cl Toluyl chloride . Melting-point. Cl = C0H5. the residue. If this is already occupied. + CCH4< = C 8 H 6 . CO . a ketone being formed: CCHC + C6HS. (3) In place of ben-zoyl chloride or acetyl chloride.times its weight of finely pulverised phosphorus pentachloride. 1400.H5 + HC1 • Diphenyl ketone =Benzophenone C6H6 + CHo. phenol-ethers.CH 8 + HC1 XX). C.C6H4< + HC1.C 0 H 4 . and recrystallise the free oxime from alcohol.CH 3 Toluene Phenyltolyl ketone In cases of this kind. Cl = p . The ether is then distilled off. Melting-point. (2) In place of hydrocarbons. their homologues can be used: Q H . and the precipitate separating out is recrystallised from alcohol. alcohol-free ether. one of the benzene-hydrogen atoms will be replaced by an acid radical. the statements made above are also true for this case. X:O. (c) A weighed amount of the oxime is dissolved in some anhydrous. at the ordinary temperature. OCH3 + C6H5. Phenylmethyl ketone =Acetophenone The reaction may be varied if (1) in place of benzene a homologue is used: QH 5 . Cl = C6H4< + HC1. CO. CO. the acid-radical always enters the para position to the aikyl radical. 163 0 . which react with extreme ease. with cooling. can be used: /OCH 3 C6H5. N:O. CH3 + C6H5. (a) If an aromatic or an aliphatic acid-chloride is allowed to act on an aromatic hydrocarbon in the presence of an anhydrous aluminium chloride. CO.C 6 H 5 Anisol Anisylphenyl ketone Concerning the entrance of the acid-radical. CH* + HC1.AROMATIC SERIES 293 changed ketone which balls together very easily on shaking. CO. it then goes to the ortho position.CO. acidify the filtrate slightly with dilute sulphuric acid. starting from o. NO2 + HCI. CO.294 SPECIAL PART QHG + CHS. Q CH 0 .and tere-phthalyl chloride x:o.C1 =C 6 H 5 .cfiH.C6H5 + 2 C6H6 = C 6 H / + 2 HCI Iso. Phenylacetyl chloride Phenylbenzyl ketone = desoxybenzoTn In this way.C 6 H 5 + HC1. Nitrobcnzophenone (5) Finally. C6H5 + 2 HO.H5.ci /CO. CO. and thus halogen or nitroketones are obtained: C6H6+C6H/ ' C O . the o.C. Cl = C6H5. Cl Brombenzoyl chloride =C 6 H 5 . etc. nitrobenzoyl chloride. Cl Nitrobenzoyl chloride = C6H5. CO. CO. the chlorides of the three following acids would be obtained: CH 3 . C6H4.C1 Nro. (4) Substituted acid-chlorides like brombenzoyl chloride. C6HS I +2C6H6=| ' +2HCI CH 2 ~CO. the chlorides of dibasic acids react with the formation of diketones or ketonic "acids: CH 3 -CO .CO. can be used..CH 2 . Phosgene Benzophenone In these reactions if but one chlorine atom should react.CH2.Br + H C I Brombenzophenone QH 6 + C6H4< X . CH 2 . Cl CH 2 . CO.and p C e H / /CO.C 6 H 4 .CO.O .H i Pcaroylpropnooic acid ^eocoylbfenzoic acid .or m-tolylphenyl ketone can be prepared. CO.CO. Z 01 CO + 2 CSH8 = C6H5. CH3 + HCI QH 6 -f C.or m-toluic acid.CO. CfiH5 Succinic chloride m1. CH 2 . it cannot be obtained by the action of benzoyl chloride on toluene. important on account of its relation to the fluorescem dyes: 2 C6H6 = C 6 H / >O + 2 HCL Phthalophenone Michler's ketone. For example. m-.g. CH3 + CH3CI = C 6 H / + HCL 3 Toluene Xylene But in this connection the reaction is in many cases. The reaction is still further complicated in that the aluminium chloride partially splits off the alkyl groups : C6Hfi. N(CH 3 ) 2 + COC12 = CO +2 HCL \QH4.N(CH 3 ) 2 2 C6H5. but varying quantities of tri-. for three reasons: First. and indeed in the simplest case. since in place of the acidchloride. penta-.N(CH3)2 The Friedel-Crafts reaction can also be used for the preparation of the homologous aromatic hydrocarbons. C2H5 + HBr /CH3 . CH3 + HC1 = CeH6 + CH3C1. thus it is often difficult to limit the reaction to the desired point. 1 &. not only is one hydrogen atom substituted. in the action of methyl chloride on toluene. 2627. fractional distillation. with the formation of dimethyl benzene. not of equal importance with its application for the ketone syntheses. and hexa-methyl benzene are also formed.. not only one of the three dimethyl benzenes. which cannot be separated like the homologues by. tetra-. the product of the reaction is a hydrocarbon which can again react. . tetramethyldiamidobenzophenone is of technical importance. in the above case. it is obtained from dimethyl aniline and phosgene. 14. e. A second disadvantage is this: In the different series a mixture of isomers is obtained. halogen alkyls may be caused to act on the hydrocarbons: 1 C6H6 + C2H5Br = C6H5. and p-varieties is formed.AROMATIC SERIES 295 From the chloride of phthalic acid phthalophenone is formed. but a mixture of the o-. and is used in the preparation of dyes of the fiichsine series (see Crystal Violet): / C 6 H 4 . Acetylene tetrabromide | | r~* "H" C* T-f s-Tetraphenyl ethane In the latter reaction.C1 C6H6 = NO 2 .CH3. the alkylene chlorides or bromides. CH 2 . C6H6 + Cl. NH2 = C6H5.CH 2 . CH 2 . Urea chloride Benzamide .C6H4. as well as tri. The reaction is also applicable to aromatic chlorides which contain the halogen in the side-chain: C6H5. Nitrodiphenyl methane As the chlorides of dibasic acids yield diketones.296 SPECIAL PART Since the lower homologues thus formed again react synthetically with the halogen alkyls. .C e H 5 + HC1.g.CH2. CO.C1 + C6H6 = C G H. anthracene is also formed. e.and tetra-halogen substituted hydrocarbons.HC1. can react with several hydrocarbon molecules. and the halogen alkyls on elimination also take part in the reaction.g.. mixtures often difficult to separate are formed. CO. CGH5 + 2 HBr Dibenzyl = s-Diphenyl ethane 3C6H6 + CHC13 = CH. NH 2 4. according to the equation: CH 'H< Anthracene For the synthesis of aromatic acids the Friedel-Crafts reaction is also of value. but derivatives of them.C ? H 4 .CH 2 . (C6H5)3 + 3 HC1 Chloroform Triphenyl methane 4C6H6+CHBr2-CHBr2 = CH — CH + 4 HBr. which upon saponification yield the free acid.: 2 C6H6 + CH2Br — CH2Br = C6H5.C 6 H 5 + HC1 Benzyl chloride Diphenyl methane NO2. In some favourable cases the reaction is of use in the preparation of the homologues of benzene. e. although the acids themselves are not directly obtained. g.CJH. certain it is that hydrocarbons as well as phenol-ethers unite with it to form double compounds which are of assistance in causing the reaction to take place.NCS Phenyl mustard oil =C 6 H 5 . Benzophenone oxime Oximes may be obtained by three methods: (i) The alcoholic solution of the aldehyde or ketone may be treated. in place of the hydrocarbons.AROMATIC SERIES C6H6 + C6H5. Concerning the role which aluminium chloride plays in the reaction.C 6 H 5 C 6 H 5 .C. the great value of the Friedel-Crafts reaction will be readily understood. ethers. forming an acid-chloride. CO. C6H5.and poly-acid phenols. and many other compounds can be used.C 6 H 5 + NH 2 .CO. it is still not perfectly clear. C H = N . which then reacts with the hydrocarbon with elimination of hydrochloric acid. NH.NCO + HC1 = CO Phenyl carbamine chloride If one considers that in the modifications. mono. or it may be heated in a flask provided with a reflux condenser. oximes1 (aldoximes. or in a bomb-tube.. ketoximes) are formed in accordance with the following typical reactions: C6H5. is. NCO = C6H5. with a concentrated water solution of hydroxylamine hydrochloride and the mixture allowed to stand at the ordinary temperature. CHO + NH2 . C6H3 Phenyl cyanate Benzanilide 297 C6H6 + C6H5. 1324. i B.OH = C6H5. naphthalene.NH. Thiobenzanilide The last two reactions are to be considered as cases of the normal Friedel-Crafts reaction. generally. diphenylynaphthol-ethers.C 6 H 5 . (b) By the action of hydroxylamine on aldehydes and ketones.OH = A.: /NH. e.CS. An addition of a few drops of concentrated hydrochloric acid often. since the cyanate and mustard oil unite in the first phase with hydrochlorid acid. OH + H2O Benzaldoxime C 6 H. . thiophene. )H N + H 2 O. for one carbonyl group three molecules of hydroxylamine hydrochloride and nine molecules of potassium hydroxide are used. to be expressed by the following formulae. This is also true when oximes are formed from many unsymmetrical ketones.C.1 Since.g.H || N—OH OH vidnal to H The stereoisomeric forms of an unsymmetrical ketone are. Since the oximes possess a weak acid character. : C. C6HS || HO—N O H vicinal to C^H^Bj4. the two following stereo-isomers are possible: QH 5 . 1343.C. but a mixture of two stereo-isomers. but that they extend into space. (3) Oximes may in many cases be very easily obtained. e.C.2gS SPECIAL PART expedites the reaction. . The existence of these isomers is explained by the assumption that the three valencies of nitrogen do not lie in a plane. || N—OH O H -vicinal to C^H. e. e. the hydroxyl-group of the hydroxylamine is vicinal to either the phenyl-group or hydrogen atom. under these conditions the alkali salt of the oxime is first obtained.g.C 6 H.. and BrC 6 H 4 . 23. C. Of especial significance for the stereo-chemistry of nitrogen are the oximes of aldehydes as well as those of the unsymmetrical ketones.H II HO—N OH vicinal to QH S and C 6 H 5 . according to this conception. if. in the presence of a large excess of hydroxylamine in a strongly alkaline solution. (2) The formation of oximes may be brought about by the use of free hydroxylamine obtained by treating its hydrochloride with the theoretical amount of a solution of sodium carbonate. proceeding from a point like the three edges of a regular triangular pyramid.g. there is formed not only a single oxime. N OK from which the free oxime is liberated by treating it with an acid. e. By the action of hydroxylamine on benzaldehyde.g.. i i . generally a very smooth decomposition takes place. in the formation of benzaldoxime. as above. 1B.: C 6 H 5 . 988.g. e.C 6 H J Bcnzanilide OH Benzophenone oxime This so-called Beckmann transformation has been of great significance for the explanation of the constitution of the isomeric oximes. CO. as follows from their saponification products. so that here oniy one oxime is possible. They are explained by the following space-formulae: C. 2Q. Br and BrC6H4. These compounds gave the impetus to the investigations1 of this class of compounds. x.1304. C. 16. NH.1985. C.. C6H4.C6H5 !! il II !l i! i HO—N N—OH HO—N HO—N N—OH HO—N Not all aldehydes and unsymmetrical ketones yield two oximes.NH. the hydroxylgroup is replaced by chlorine: 1 B.C C H 5 C6H5.. but two different ones. In many cases one form is so unstable (labile) that only the other (stabile) modification exists. (c) If phosphorus pentachloride is allowed to act on an oxime.g. In this place the two mono-oximes and three dioximes of benzil may be referred to again. phosphorus pentachloride is allowed to act on both of the above formulated stereoisomeric oximes of the brombenzophenone. C6H5 C6H5. C. 784. .2 e. CSH5 The transformation takes place.: N I =C ti H 3 .H5 H and j) HO-N N-OH C 6 H 5 . CO. to the brombenzoyl derivative of aniline: C6H5. the same compounds are not obtained from both.1996.537. which.CO.C6H5 QH 5 . 9 B. 503. in the following way: If phosphorus pentachloride is allowed to act on an oxime. 21. NH. on the other. probably. $507 and 2580 • A. correspond on the one hand to the benzoyl derivative of bromaniline.564. CO. 22. If.C.C C.H5. 252.AROMATIC SERIES ^ 259! With symmetrical ketones it is obviously immaterial upon which of the two similar sides the hydroxyl-group finds itself.C C. it is transformed into an anilide. 19. and.C. CO. 3510. OH + C6H5NH2 Brombcnzoic acid anUinc . benzanilide is formed.C C H. that the chlorine atom gives up its position to the vicinal hydrocarbon radical.CO.H4Br and Br. C. 134) —>- If this is now treated with water. Q H 5 Bcnzoyl bromanilidc and Br.C1 !! N QH5 Imidochloride of Benzanilide (Compare p. C5H5 :i Cl—N Cl vicinal to C.. there are formed: C1. the chlorine atom being replaced by a phenyl-group : C 6 H 5 . C6H5 Brombenzoyl anilide Upon saponifjcation. there are obtained: Br. is unstable.. by treatment with water.C.C 6 H 4 . C6H5 il N—Cl Q vicinal to Q H 6 If the most probable assumption is now made. these yield : CO. CO.C 6 H 4 . C. CO. and it is immediately transformed into a more stable imidochloride. NH . C 6 H 4 .CC 6 H 5 <! N Cl C 6 H 5 . C 6 H 4 . in which chlorine is united with nitrogen. the unstable chlorides are first obtained: Br. N H . Q H 4 . C 6 H 5 •C.C 6 H.C 6 H S Br. N H .30O SPECIAL PART C. CO. C.N and II N. in accordance with the following equation: > C 6 H. ii +HCI4-POCI3 + PCIS = N OH i But a compound of this kind.Cl !! Br. Cl = N .C.OH Bns«aailiac Beaxoic acid and Br. is subjected to a similar reaction.C C H 5 from which.C S I *. C 6 H 4 .C. formulated above. C6H5 + HC1 If the oxime of brombenzophenone. C6H5 + HX> = CCH5. is. Whatever may be the space configuration of the stereoisomeric aldoximes. and yields a niN. .AROMATIC SERIES 301 That hydrocarbon radical which in the oxime was vicinal to the hydroxyl-group. e. is an extremely energetic reducing agent. C H C ~ N I C6H<<5. as in the above case. while in the second case it is vicinal to the hydrocarbon residue: C G H 5 . poured into a small separating funnel. Hydriodic acid. while the other two forms do not. The reaction-mixture is then treated with ether. The reducing action depends on the following decomposition: 1 B. REACTION: REDUCTION OF A KETONE TO A HYDROCARBON EXAMPLE : Diphenyl Methane from Benzophenone1 A mixture of 10 grammes of benzophenone. H Owing to the nearness of the oxygen and hydroxyl. especially at high temperatures. the diphenyl methane solidifies to crystals which melt at 270. C. the derivatives containing an acid radical (acetyl derivative) of the one form easily yield an acid-nitrile on being treated with soda. which can be used to effect reduction when. Syn-Oxime . it loses OH water easily. could not be employed. and the residue distilled. obtained in the form of a primary amine. another reducing agent. H Yields no II nitrile. almost quantitative. In this way.g. see page 62.N Anti-Oxime 34. 1624. 12 grammes of hydriodic acid (boiling-point. The hypothesis proposed. 1270). therefore. Boiling-point. suggests that in the first case the acid radical (or in the corresponding oxime) the hydroxyl-group is vicinal to the aldehyde hydrogen atom. and shaken up with water several times. and dried. On cooling. 2 Before opening the tube.. HO. Yield. on saponification of the polymerised product.C. The ethereal solution is filtered through a small folded filter.^ a metal and acid. the ether evaporated. 7. 263 0 . the constitution of the stereoisomeric oximes of the unsymmetrical ketones is determined. and 2 grammes of red phosphorus is heated in a sealed tube 2 for 6 hours at 160 0 . which seems very probable. . CO.CGH5 + H 2 0 + 2 I. CH8 + H 2 0 + 41 Toluene = CCH5. CH3 + 2 H 2 0 + 3 I2 Toluene Octodecane C 17 H 35 ..f P ( O H ) . iodides.g. .: C6H5. OH + 6 HI CH 2 . OH + 6 HI = C 18 H 38 + 2 H 2 0 + 3 I 2 Alcohols.302 SPECIAL PART The above reaction takes place in accordance with the following equation: C6H5. the liberated iodine unites with the phosphorus to form phosphorus tri-iodide: 3 l + P = PI s which with the water present again decomposes to form hydriodic acid: PI 3 + 3 H 2 O = 3 H I . C6H5 + 4 HI = C 6 H 5 .: C 6 H 6 +6HI =C 6 H 13 + 3 I 2 Hexahydrobenzene The effect of hydriodic acid is increased by the addition of red phosphorus. = C2H6 + I2 Ethane CH 2 . Diphenyl methane With the aid of hydriodic acid.: C2H5I + HI Ethyl iodide . Under these conditions. CH.CO. provided a sufficient quantity of phosphorus is present. the hydrocarbons. act as a continuous reducing agent. e. can also be reduced to their final reduction products. e. the unsaturated compounds take up hydrogen.CHO + 4 HI C 6 H 5 . CO .OH + 6HI Benzoic acid Stearic acid = Q H 5 . during the course of the reaction. Phosphorous acid A definite amount of hydriodic acid can thus. not only ketones but also aldehydes and acids may be reduced to the hydrocarbon from which they are derived.0H Glycerol CH3 = CH2 + 3 H 2 0 + 3 I 2 CH3 Propane By heating with hydriodic acid.g. etc.g.0H CH. e. 31. After the apparatus has been fastened firmly in a clamp it is immersed into a casserole rilled with water at 200. . the temperature rises to 25-30 0 . The hydrochloric acid is generated in a Kipp apparatus from fused ammonium chloride and FlG concentrated sulphuric acid. IB.30. in the middle hole is inserted a glass tube which carries a stirrer (paddle wheel of glass) . The carbon monoxide. not too rapid. is passed first through a solution of caustic potash ( 1 : 1 ) and then through a wash-bottle containing concentrated sulphuric acid.1149. add. contained in a gasometer of about 10 litres. 45 grammes of pulverised. freshly prepared aluminium chloride and 5 grammes pure cuprous chloride (see page 355). The escaping gas is led directly to the hood opening.AROMATIC SERIES 3O3 3 5 .1622. 75). A current. not too quickly. The gas currents are so regulated that the volume of the carbon monoxide is about twice as large as that of the hydrochloric acid. of carbon monoxide and hydrochloric acid gas is led in through the prong-shaped tube while the stirrer is set in motion (a small motor is convenient). the remainder of the gas is passed in during four to five hours. The vessel is closed by a three-hole cork. REACTION: ALDEHYDE SYNTHESIS — GATTERMANN-KOCH EXAMPLE : p-Tolylaldehyde from Toluene and Carbon Monoxide1 To 30 grammes of freshly distilled toluene (boiling-point n o ° ) contained in a wide-necked vessel (an " extract of beef" jar is convenient) cooled with water. the other holes are used for the inlet and outlet tubes (Fig. In the course of an hour when about 1-2 litres of carbon monoxide have been passed into the mixture. It is passed through a wash-bottle containing concentrated sulphuric acid. Upon evaporating the ether. The toluene. and then into a gasometer (Fig. is separated in a dropping funnel. As soon as the oxalic acid has dissolved and a regular current of gas comes off. remaining undissolved. The distillate— oil and water — is then shaken up with a sodium bisulphite solution for a long time. If the aldehyde-bisulphite compound should crystallise out. the reaction may be stopped. 204°/ Preparation of Carbon Monoxide In a round litre flask heat 100 grammes of crystallised oxalic acid with 600 grammes of concentrated sulphuric acid. At first the sulphuric acid is heated somewhat strongly. from 20-22 gramriies off perfectly pure tolylaldehyde remains. ing a match. Boiling-point. 76. So long as air remains in the apparatus. 74) filled with a solution of caustic potash (1 part caustic potash to 2 parts of water).304 SPECIAL PART If the reaction-mixture should become so viscous before the lapse of this time that the stirrer revolves only with difficulty. It is extracted from the distillate with ether. But as . water is added until it dissolves. The gases evolved are passed into two large wash-cylinders (Fig. The viscid product is then poured into a large flask containing crushed ice. The filtered water solution is then treated with anhydrous soda until it shows a decided alkaline reaction. the aldehyde formed and any unattacked toluene is distilled over with steam. the aldehyde is then again distilled over with steam. 76). the flame is lowered. Before filling the gasometer the gas is tested by collecting a test-tube full over water and applyFIG. a slight explosion will occur. and care is taken not to breathe the gas. the apparatus is taken apart.and m-xylene.C1 = CO + HC1 If it were stable. When the evolution of gas ceases. If the gas be passed first into two caustic potash cylinders. A direct synthesis of the aromatic aldehydes by means of the FriedelCrafts reaction could not be brought about until recently. The Gattermann-Koch synthesis may be expressed by the following equation: /CH3 From other hydrocarbons like 0. it burns quietly in the tube. in accordance with this equation: But now it is known that a mixture of carbon monoxide and hydrochloric acid in the presence of cuprous chloride^ which combines with the former. If it is desired to avoid the use of a gasometer. because of the instability of formyl chloride. zene. and then into two sulphuric acid (cone. the acid radical the para position to the alkyl residue. behaves like formyl chloride. it may be used directly for the synthesis. mesitylene. is heated in an oil-bath to 120 0 .AROMATIC SERIES 305 soon as pure gas is evolved. it should form aldehydes.CO. so also in the aldehyde ethylbenobtained. goes into syntheses . etc.. provided with a safety-tube. Since carbon monoxide is poisonous. which. It is then admitted into the gasometer. the experiment is carried out under the hood. the temperature is gradually increased according to the conditions. in an analogous way. diphenyl.) cylinders. aldehydes may be As has been shown in the ketone syntheses. containing 200 grammes of oxalic acid and 200 grammes of sulphuric acid (cone). a regular and continuous current of carbon monoxide may be generated as follows: A litre flask. if formed. decomposes immediately into carbon monoxide and hydrochloric acid: H. under the influence of aluminium chloride. reacts with the phenol ether. hydrocyanic acid is used in place of carbon monoxide . /0CH8 .. yields the corresponding aldehydes far more easily than the same reaction applied to the hydrocarbons. The action takes place.. when applied to phenol ethers. in these cases the presence of cuprous chloride is unnecessary. liberating hydrochloric acid: 'OCH* . If it be desired to obtain aldehydes from them. due to the union of hydrocyanic and hydrochloric acids to form the chloride of imidoformic acid: V which. it is remarkable that the Gattermann-Koch method cannot be used with phenol ethers.306 SPECIAL PART the aldehyde group always enters the para position to the alkyl residue Thus from toluene there is obtained: :OH From o-xylene- From m-xylene- COH Since the Friedel-Crafts reaction. for instance. Thus. anilides. the acid separating out is filtered off and washed several times with water. substituted amides. amides. After cooling it is diluted with water. It is. 1770. acetamide reacts on heating with a solution 1 A. Saponification may be conducted either in an alkaline or an acid solution.AROMATIC SERIES 307 There is thus obtained first the aldehyde-imide which.. 80-90% of the theory. the pure acid is obtained. passes over into the aldehyde with great ease: yOCH 3 /OCH. the carbon dioxide is absorbed. A small portion is dissolved in a little alcohol.Yield. through the action of acids. By saponification in a narrow sense is understood the splitting up of an acid-ester into an alcohol and acid.g. REACTION: SAPONIFICATION OP AN ACID-NITRILE EXAMPLE : Toluic Acid from Tolyl Nitrite1 The p-tolyl nitrile obtained in Reaction 10 is heated with slightly diluted sulphuric acid on the sand-bath in a round flask with reflux condenser until crystals of toluic acid appear in the condenser. The carbon monoxide is obtained in accordance with the following equation: COOH I = CO + COo + HoO COOH The mixture of gases is separated by passing it through a solution of caustic soda or caustic potash. . For each gramme of the nitrile a mixture of 6 grammes of concentrated sulphuric acid with 2 grammes of water is used. 36. it is then boiled some time with animal charcoal.10. and hot water added until the solution just becomes turbid. . C6H4< = NH3 + Q H / \CH=[NHTH^O \CHO In this way it is possible to introduce the aldehyde group into phenol ethers as well as into the phenols. Melting-point. into acids of the same name. and the carbon monoxide emerges in a pure condition. used in a wider sense to indicate the conversion of acid-derivatives. however. 258. like nitriles. e. On cooling. it acts on the phenol-ether in the manner indicated by the following equation: 3 C.: CH3 /CH8 H / 2 H2O = C . COOH + N2 + H8O In order to saponify a nitrile by this method it is first converted by heating with 85 % sulphuric acid into the amide.308 SPECIAL PART of caustic potash or caustic soda with the formation of the alkali salt of acetic acid and the evolution of ammonia. Further. H / + NH 3 0 \CCN \CO. Such decomposition cannot be effected by the methods hitherto given. upon heating. cooling. saponification may be effected by heating with a sodium carbonate solution under pressure. alcoholic caustic potash or caustic soda can be used for a similar purpose. decomposes them into the phenol and the alkyl iodide: C6H5. Nitriles and esters may frequently be saponified by water solutions of the alkalies. In order to effect saponification in acid solution. would be changed. and this is treated as directed above. the free phenol will separate out. OH + CH3I Anisol Anhydrous aluminium chloride may be used here with great advantage. OCH3 + HI = CCH5.g. Finally. 32. when heated with phenol-ethers.g. e.: CGH5.?73. 28. The decomposition of the ethers of phenols is also designated as saponification.OH p-Tolyl nitrile p-Toluic acid Acid amides may be easily saponified by dissolving in concentrated sulphuric acid. 917. . 1118. and then gradually heating. the substance to be saponified is heated with either hydrochloric acid or sulphuric acid in varying degrees of dilution. Ref. adding sodium nitrite. This method presents the advantage that it may be applied to substances containing. l B. Frequently it is better to allow the nitrite to act directly on the warm dilute sulphuric acid solution of the amide.. 26. if treated with hydriodic acid. in addition to the phenol-ether radical. Hydriodic acid is used which.. this method is especially well adapted for difficultly saponifiable amides or anilides.1 e. a reducible carbonyl group. R£f.H.H. which. CO. O)3A1 + 3 CH3CI Aluminium salt of phenol If a phenol salt is treated with an acid. OCH3 + AICI3 = (C. NH 2 + NOOH = C6H5. this is washed with hot water. is acidified with concentrated hydrochloric acid. Terephthalic acid is insoluble in water.. After cooling.AROMATIC SERIES 37. and dried on the water-bath. it sublimes without melting. /CO. CO. either all or a portion of them may be converted into carboxyl groups: /CH 3 3 gives H3 OH \CO. CH3 + 3 0 = C6H. OH X C 6 H// 6H \CO.OH QH^CO. REACTION: OXIDATION OF TEE SIDE-CHAIN OP AN AROMATIC COMPOUND 309 EXAMPLE : Terephthalic Acid from p-Toluic Acid Dissolve 5 grammes of the crude toluic acid obtained in Reaction 36 in a solution of 3 grammes of sodium hydroxide in 250 c. united with the benzene nucleus. OH + H2O Toluene Benzole acid If several side-chains are present in a compound.OH ^COOH . \ . 90 % of the theory. the red colour of the permanganate no longer vanishes. Yield. and. to pass over to carboxyl groups on oxidation. of water \ heat in a porcelain dish on the water-bath. washed with water. OH /CH3 /CO. and the nitrate.c. the manganese dioxide separating out is filtered off. the terephthalic acid is filtered off. and gradually treat with a solution of 12 grammes of finely powdered potassium permanganate in 250 c. A methyl group requires 3 atoms of oxygen for oxidation: Q H 5 . after long boiling. after cooling. Alcohol is then added until the liquid is colourless. It is a common property of aliphatic side-chains. heated to boiling.c. of water until. On heating. it is desired to convert p-toluidine into p-amidobenzoic acid. CH3 \ N H . the base is first acetylated. : /CH3 /CO. Derivatives of hydrocarbons are also capable of similar reaction. with the exception of the last. e. CO.g. and the desired amidobenzoic acid is formed: / C O . in many cases only the methyl group at the end of the chain can be oxidised.g.OH \NH.. e.CH 3 + 3 O2 = C 6 H 5 . CH3 The acid thus obtained is then saponified.OH + CO2 + 2 H2O Ethyl benzene The basicity of the acid derived from the oxidation of a hydrocarbon accordingly gives an indication concerning the number of side-chains of the hydrocarbon. and the acetatoluide is then oxidised: /CH3 C6H/ / C O . CO. CO. OH C6H4<( + 3 O = C6H4< +H 2 O \CO.CO.CH3 \CQ.g. C6H4<( +H 2 O = C 6 H 4 < " +CH3. CH 3 + 3 O = X .OH C6H4<^ + 3 O = C6H4<^ +H2O Chlortoluene Chlorbenzoic acid • / C O . OH + 3 0 = C6H4< + H2O NO 2 \NO2 Nitrotoluene Acetophenone Nitrobenzo'ic acid Phenyl glyoxylic acid H3 CH 3 .OH .g.OH \CO. by which the former are converted into an acid derivative. and the latter into an ester.CO. CH 2 . CO. C6H5 + 3 0 = C 6 H 5 . e. OH +3O = C6H/ +H 2 O \ N H . but an indirect method must be employed.CO.0H Amines and phenols cannot be directly oxidised in most cases. e. CO . OH /NH. : X .CH 2 . CH 2 . : C 6 H 5 .3IO SPECIAL PART If a side-chain contains several carbon atoms. If. COOH + H2O The reaction carried out above takes place in accordance with this equation: /CH3 / C O . OH + H2O But by an energetic oxidation all the carbon atoms. are split off. e.g. or as a water solution of potassium dichromate or sodium dichromate acidified with dilute sulphuric acid. manganese dioxide is deposited: 2 KMnO4 + H2O = 3 0 + 2 MnO2 + 2 KOH Two molecules of potassium permanganate yield. no manganese dioxide separates out. nitric acid to 3 vol.OH Nitric acid is also used in other cases. other oxidising agents totally destroy the substance. An excess of the permanganate can be removed by the addition of alcohol or sulphurous acid. The mildest effect is obtained with the nitric acid. to form manganous sulphate: 2 KMnO4 + 3 H 2 SO 4 = 5 0 + K2SO4 + MnSO4 + 3 H2O Two molecules of the permanganate in acid solution. 1057. but also for the oxidation of alcohols. not only in the case in hand. 137. 4 1 . With potassium permanganate 2 oxidation can be effected either in alkaline or in acid solution. therefore. yield 5 atoms of available oxygen. to oxidise a phenol. In oxidation reactions. dissolved in glacial acetic acid..: C (! H/ y3 \CO. cresol.or phosphoric acid-ester of it is first prepared and oxidised. 55 parts of concentrated sulphuric acid.{ + 3 O For the oxidation of aromatic hydrocarbons. 1 A.g. which is therefore used when all the side-chains are not to be oxidised. chromic acid or potassium permanganate is used.1 experience has shown that a good oxidising mixture is 40 parts of potassium dichromate. As oxidising agent. In acid solution (sulphuric acid). the sulphuric acid. diluted with twice its volume of water. since it is dissolved by the sulphuric acid. 7. three atoms of oxygen. In the first case. where. /CH3 C6H4<^ . cone. . ketones. therefore. but only a portion of them. two molecules of chromic anhydride (CrO3) give three atoms of oxygen: 8 2 CrO3 = C2O. dilute nitric acid (1 vol. Chromic acid. in alkaline solution. the reaction-product is then saponified.. 2 B. on the other hand. in the form of its anhydride generally. In oxidising with potassium permanganate. 302. a 2-5 % solution is generally used. as frequently happens with ortho derivatives. water1). with evolution of oxygen. e. can also be used as an oxidising agent. 133. etc.AROMATIC SERIES 311 If it is desired. 423. The residue. on gentle shaking the liquid becomes a fuchsine-red in colour. When the reaction is complete the chloroform is distilled off with steam. After 10-15 minutes the second third of the chloroform is added. observing the precautions just given. . especially during the last phase. When it reaches 700 the entire flask is immersed in cold water until the thermometer indicates 650. of water by heating. 15. cool the solution without shaking to 60-650 by immersion in cold water. The distillate is then extracted with ether. after about 20 minutes. and is acidified carefully with dilute sulphuric acid. REIMER AND TIEMANNi EXAMPLE : Salicylic Aldehyde from Phenol and Chloroform In a round litre flask dissolve So grammes of caustic soda in 80 c. In this way during the entire reaction the temperature is always kept between 650 and 700. and the temperature rises. etc. increases the yield materially. 2685. The synthesis requires in all from i } t o 2 hours. By means of a two-hole cork attach to the flask an effective reflux condenser. Add 25 grammes of phenol. Frequent shaking of the mixture.c. upon which it becomes almost colourless. After a short time the colour changes to orange.312 SPECIAL PART 38. as follows : At first add one-third through the condenser. is treated 1 B. 824. Finally. the remainder of the chloroform is added. and the ether evaporated. Add 60 grammes of chloroform gradually. Should it fall below 6o°. consisting of unchanged phenol and salicylic aldehyde. 9. 10. REACTION: SYNTHESIS OF OXYALDEHYDES. finally. Since toward the end the reaction takes place very quietly. the mixture is warmed by immersing it a short time in hot water until the mercury rises to 65 °. The orangecoloured alkaline liquid is allowed to cool somewhat. the flask is frequently immersed in hot water in order to maintain the temperature between the prescribed limits. the ethereal solution separated from the water. steam is passed into it until drops of oil no longer go over. 1562. and insert a thermometer the bulb of which dips into the liquid. the ether is evaporated. 2-3 grammes.ONa -f CHCL + 3 NaOH = C ( i H/ + 3 NaCl + 2 H2O S XIHO CHO Probably the reaction takes place in the two phases: (i) C /OH H/ . lustrous leaflets are then well pressed out on a porous plate and the aldehyde set free by a gentle warming with dilute sulphuric acid on the waterbath. the mixture is extracted with ether. and the filtrate extracted with ether. which. After standing from £-1 hour the crystals are filtered with suction. and the residue of the pure aldehyde is distilled. and remains back in the. In order to obtain it. upon which the p-oxybenzaldehyde separates out at once or on standing. and washed several times with alcohol to remove completely the adhering phenol. and finally with ether. Upon stirring well for a long time with a glass rod. the residue remaining in the flask after cooling is filtered through a folded filter.AROMATIC SERIES 313 with twice its volume of a concentrated solution of commercial sodium bisulphite. a further quantity is obtained. 10-12 grammes. and the clear filtrate saturated with solid salt. The small amount of the p-oxybenzaldehyde formed with the salicylic aldehyde is not volatile with steam. On cooling. = HC1 + /OH C0H4< X 6 1 H + C11C H C12 /OH CHC1 2 /OH M:HO . together with the first. Yield. Boilingpoint. Melting-point. is purified by recrystallisation from water with the addition of a solution of sulphur dioxide. Yield. a solid paste of the double compound of the aldehyde and bisulphite should separate out. pressed firmly together. If this be filtered off. the ethereal solution dried over anhydrous Glauber's salt. 1960. The pearly. 116°. The synthesis takes place in accordance with this equation: y ONa C(tH. flask after the distillation with steam. also a dialdehyde unv f DH CH'0 | \ /OH CHO Gentisin aldehyde. CHO CH3 p-Cresol —*- f 1 OH / \\ATT I CHO T . it enters the ortho and para positions to a hydroxyl group: Phenol gives o. 3 and Vanillin. m-Cresol —>f | and ^CHO CH.and p-oxybenzaldehyde. Resorcin —>- Hydroquinone —>- 0 0 OH OH OH OH . CH3 o-Cresol — > I and CH3 onc\y CH. The reaction also takes place with the ethers of poly-acid phenols.„. Thus guaiacol gives: OH OH OHC/\OCH3 / \ O C H 3 x r .314 SPECIAL PART By this method the aldehyde group may be introduced into monoand poly-acid phenols. CHO . onlv ' Pyrocatechin —>• ( = Protocatechuic aldehyde. .AROMATIC SERIES From resorcinmonomethyl ether there are hydes and two dialdehydes. But it has some defects. the separation of the mixture of the mono. /OH This synthesis is capable of very wide application.C< ~ Further. yields a dialdehyde. The reaction is aldehydes as well as oxycarbonic acids. From the three oxybenzoic acids are formed two oxyaldehyde acids. in addition to a monoaldehyde.OH }H == HoO -I. has always been mentioned. and another portion reacts with the chloroform to produce an ester of ortho formic acid: 3 C6H5ONa + CHClg = 3 NaCl + CH(OC 8 H 5 ) 3 A portion of the aldehyde first formed is lost by condensation with some unattacked phenol. The yield is very much decreased by the fact that a portion of the phenol does not enter into the reaction. Thus there is formed a mixture of two oxyisophthalic /OH *\:HO OH p-oxybenzaldehyde gives I ives: 3IS formed two monoaldealso applicable to oxyfrom salicylic aldehyde aldehydes: /\cHO I CHO That resorcin.and dialdehydes is often attended with serious difficulty. forming a derivative of triphenylmethane: C(5H4. Thus the yield of aldehyde obtained in accordance with the original directions leaves much to be desired. In addition. a portion of the oxyaldebydes is converted into resins by the alkali. and finally they may be applied to phenols like pyrogallol. etc. These reactions possess many advantages over those discussed above. There is first obtained a caked. With these substances the other reaction is useless. hydrocyanic and hydrochloric acids.39. poly-acid phenols of naphthalene. 77. and with stirring. yield only the p-oxyaldehydes. REACTION: KOLBE'S SYNTHESIS OP OXYACIDS EXAMPLE : Salicylic Acid from Sodium Phenolate and Carbon Dioxide 1 Dissolve 12^ grammes of chemically pure sodium hydroxide in 20 ex. but is kept in constant motion. zinc chloride. and FIG. 32. 278.397. further. etc. . 1765.W I0>*9.) 39. the mass being continually stirred.SPECIAL PART As already mentioned on page 306. the heating is continued with a luminous flame. of water in a porcelain dish. phloroglucin. The greatest portion of the water is then evaporated by heating over a free flame. In order to fasten the dish. treat gradually with 30 grammes of crystallised phenol. the aldehyde group may be introduced into phenols by the use of condensation agents like aluminium chloride. 31. which is crushed from time to time with a mortar-pestle. and introduce only one aldehyde group. which is not placed directly under the dish. or better a nickel dish. They take place more smoothly. the two naphthols. (See B. bright-coloured mass. only small amounts of resins are formed. a pair of crucible tongs is clamped in a vertical position. As soon as a crystalline film forms on the surface of the liquid. the dish supported between its jaws. 27. 19. As soon as the particles no longer M-pr. one should use for this experiment a tube of 2.. After the reaction-mixture has been cooled with ice-water a long time. in a dry condition. The preparation of salicylic acid does not always take place . capacity. The temperature is then gradually raised (200 per hour) during the course of four hours. a not too rapid current of steam at a temperature of 170-180° (see page 40) is passed over it.c. while a not too rapid current is passed in. is placed in a short-necked flask. The connecting tube between the flask and condenser must be 2 cm. Since the acid distilling over very soon stops up a condenser tube of the usual width. This is heated to n o 0 . After cooling. the phenol in the neck of the retort is melted by the application of a flame to the outside.AROMATIC SERIES 317 bake together. and pressed out on a porous plate. 156°. The connection between the flask and steam generator must not be made until the oil-bath and the steam have the same temperature. For this purpose the acid. the dry mass is then heated with thorough stirring in a nickel dish to dusty dryness. length of same 75 cm. above the upper surface pf the sodium phenolate) . During the operation the mass is stirred several times with a glass rod. fine powder is poured into a large beaker. The mixture is finally heated 1-2 hours at 2000. to 1900. washed with a little water. the mass is pulverised quickly in a dry mortar. the retort is washed out several times with water. long colourless needles separate out on cooling. The retort is then immersed as far as possible in an oilbath (Fig. It is then placed in a tubulated retort of 200 c. this is passed into the retort for an hour. Meltingpoint. 5-10 grammes. and at this temperature a current of dry carbon dioxide is passed over the sodium phenolate (the end of the delivery tube is 1 cm. and the sides of the vessel rubbed with a glass rod.5 cmwidth (width of mantel 5 cm. the dusty.). The purification of the crude salicylic acid is accomplished best with superheated steam. and the salicylic acid precipitated with much concentrated hydrochloric acid. If the acid removed from the condenser be dissolved in the watery distillate in the receiver by heating. Yield. the crude salicylic acid is filtered off. and heated in an oilbath to 1700. wideband as short as possible. 77). CO2 = C 6 H 5 . there is great probability that the experiment will be unsuccessful.) C6H5. The success of the experiment depends particularly on the conditon of the sodium phenolate. as in the other. so that it may be allowed to stand in a sulphuric acid desiccator over night. Kolbe. therefore.3i8 SPECIAL PART successfully the first time. is converted into salicylic acid. the sodium phenyl carbonate is first prepared. the second half being obtained unchanged. the mass must be cooled to n o 0 before the latter is led in. the^sodium phenyl carbonate is transformed into the so-called neutral sodium salicylate: /OH (II. the carbon dioxide is added to the sodium phenolate. ONa = C6H / O. The operation should be so arranged that the sodium phenolate is prepared toward evening. According to this method. A modification of the Kolbe synthesis which permits the immediate conversion of all the phenol into salicylic acid is known as Schmitt's synthesis. The drying in the current of carbon dioxide is begun immediately next morning. In the first.ONa + C6H5. which forms sodium phenyl carbonate: .CO 2 Na = C6H4<^ while in the last phase a molecule of this salt reacts with a molecule of unchanged sodium phenolate in the following way: + C6H5. Only one-half of the phenol. OH These two latter reactions take place during the gradual heating up to 2oo°.) QH 5 . The synthesis is named after its discoverer. CO2Na In the above experiment this reaction is completed during the heating up to no° for one hour.O. which must be perfectly dry} If it " cakes " on heating the retort. ONa 4. . this is then further heated in an 1 The experiment is more certain of success if the sodium phenolate is heated a half hour in a current of dry hydrogen at 140° (retort in the oil-bath) before the introduction of the carbon dioxide. (I. It takes place in three phases. In the second phase.0.ONa XTO. for the preservation of meat. CO. heated in carbon dioxide up to 1500. Instead of preparing the sodium phenyl carbonate with gaseous carbon dioxide. With these compounds the reaction begins if the phenol is boiled in a water-solution of ammonium carbonate or potassium hydrogen carbonate. It is volatile with steam. potassium phenolate is used..g. e.g. yield chlorinated salicylic acids. It may easily be recognised. From the two naphthols C10H7.OH the oxy/OH naphthoic acids C10H6<^ . The carboxyl group under these conditions primarily seeks the ortho position to the hydroxyl group.OH /OH + HO. With acid-ethers of poly-acid phenols which still con/OCH 3 tain a free hydroxyl group. e.and meta-modifications. guaiacol.: . The addition of carbon dioxide is effected with greater ease in polyacid phenols. the . The potassium phenolate. since its water solution gives a violet colour with ferric chloride. can be obtained.OK Salicylic acid is prepared technically on the large scale. since from each mon-acid phenol. an increasingly larger quantity of the para-acid is obtained. OH If in the Kolbe reaction instead of sodium phenolate. for this reason it must not be boiled too long in an open vessel when it is to be recrystallised. also yields salicylic acid. for the disinfection of wounds. this reaction X)H likewise takes place. and not the ortho-acid. a carbonic acid may be obtained in the same way as that used above. OK = C6H3f-OH + H2O H \CO.AROMATIC SERIES 319 autoclave under pressure to 1400. like the sodium phenolate. but if the temperature is increased. in this action it differs from the para. until finally at 2200 the potassium paraoxybenzoate is the only product. and the potassium phenyl carbonate thus formed. C6H4( . the sodium phenolate may be mixed directly with liquid or solid carbon dioxide in the autoclave. the para-oxybenzoic acid is obtained. the three chlorphenols. e. The derivatives of phenols. All ortho-oxycarbonic acids show this property. upon which it is completely transformed into sodium salicylate according to Equation II. Since it is an excellent antiseptic. XX). The Kolbe synthesis is capable of very common application. as. first absorbs carbon dioxide. it finds extensive application in preventing fermentation.g. . After the liquid is cold. the base adhering to the sides of the flask is washed with water several times.CO. — A mixture of 50 grammes of dimethylaniline and 20 grammes of benzaldehyde is heated in a porcelain dish. 206. until no drops of it pass over. 217. it decomposes into carbon dioxide and phenol: . the water is poured off. Steam is conducted into it. If salicylic acid is heated strongly. After filtering. in the form of a viscous mass. 324. after cooling. while hot. REACTION: PREPARATION OF A DYE OF THE MALACHITE GREEN SERIES EXAMPLE : Malachite Green from Benzaldehyde and Dimethylaniline 1 (a) Preparation of the Leuco-base. is melted by covering it with hot water. for 4 hours. a second crystallisation may be obtained.) This viscous mass. these are filtered off. which has been previously fused in a porcelain dish. with frequent stirring. which adheres firmly to the walls of the distilling flask. on the water-bath. upon which the base separates out in colourless crystals. but separate out in an oily condition. (See p. it is transferred to a ^-litre flask. There is thus obtained the non-volatile leuco-base of the dye. which frequently happens after 1 A. and dried in the air on several layers of filter-paper. on the water-bath. Should the base not crystallise.250. and pulverised. washed with alcohol. which cannot be poured directly out of the dish. on the water-bath.83. By concentrating the mother-liquor.320 SPECIAL PART meta.and para-isomers are not volatile with steam. 40. OH C«H/ =< X)H The para-oxycarbonic acids show the same property while the metaacids are stable. with 20 grammes of zinc chloride. and heating it at the same time. and then dissolved in the flask with alcohol. the solution is allowed to stand over night in a cool place. then. and refer to a table to find out how much anhydrous acid the solution contains. of water. and from this calculate how much of the solution must be taken in order to get the required amount of the anhydrous acid (2. then add a solution of 10 parts of Glauber's salt and 50 parts of water. with frequent stirring. by weight. and treated with 10 parts of 40 % acetic acid (sp. The colourless solution of the leuco-base is then diluted in a large flask with 800 parts. more alcohol is added. The peroxide is weighed off in a beaker. washed with a little saturated sodium chloride solution. The residue remaining in the beaker after the first emptying is washed out with water. After the addition of the peroxide. then a saturated sodium chloride solution is added. by weight. and pressed out . The precipitated dye is filtered off witji suction. The filtrate is treated with a filtered solution of 8 parts of zinc chloride dissolved in as small a quantity of water as possible. In this case. For the purpose.7 parts. prepared by gradually diluting glacial acetic acid with water.0523). this is due to the fact that an insufficient amount of alcohol has been used.) a quantity of freshly prepared lead peroxide paste corresponding to 7. until all the dye is precipitated.AROMATIC SERIES 321 a short standing of the filtered solution. of the completely dry leuco-base by heating in a quantity of dilute hydrochloric acid corresponding to 2. This is easily recognised by bringing a drop of the solution. the mixture is well cooled by throwing in pieces of ice. the solution is then filtered off through a folded filter from the precipitated lead sulphate and chloride. of anhydrous hydrochloric acid. dilute pure concentrated hydrochloric acid with double its volume of water. and the mixture heated until the oil is dissolved. the reaction-mixture is allowed to stand five minutes. by weight.5 grammes of pure lead peroxide. with a glass rod on a piece of filter-paper. gradually add (during 5 min. 1. and treated with a quantity of water sufficient to form a very thin paste. with frequent shaking. (b) Oxidation of the Lenco-base.7 grammes). determine the specific gravity of the diluted acid. a bluish green precipitate surrounded by a circle of a still fainter bright green colour will be formed. gr.—Dissolve 10 parts. passes over to the dye.322 SPECIAL PART on a porous plate.CH 0+ . At present. H4. In order to purify it further. The reaction just carried out.N(CH3)2C1 The union.N(CH 3 ) : . and from the filtered solution. which. the dye formation was believed to take place in accordance with the following equation: + H2O.C 6 H 4 .C 6 H 4 .N(CH 3 ) 2 Tetramethyldxamidotriphenylmethane = Leuco-base of Malachite Green The substance thus obtained is not a dye. it may be dissolved again in water. the view that the latter is determined by the presence of the quinofie-like secondary benzene residue is generallyaccepted. or Bitter Almond Green. after cooling. the following reaction takes place: C6H5. but the reduction product of the real dye. is also used in the large scale for the preparation of Malachite Green. Formerly. on oxidation.N(CH S ) 2 _ c /c 6 c H 5 4 . discovered by Otto Fischer in 1877. In the formation of the leuco-base. . it is again thrown out by sodium chloride. was considered to be the condition which determined the nature of the dye. effected by the oxidation between the pentavalent nitrogen atom of the dimethyl aniline residue and the common methane-carbon atom. and the formula of the dye-salt is written thus: = Quinoide formula of Malachite Green. is formed. and heat in an 1 A. it may be pointed out in this place that. 41. instead of dimethyl aniline. and the dye is now prepared exclusively by Fischer's method. since the preparation of pure benzotrichloride on the large scale is difficult. Still. which was discovered by Dobner: it consists in heating benzotrichloride with dimethyl aniline in the presence of zinc chloride: Cl H . substituted benzaldehydes. an analogous substance.1 (£) Bromination of Fluorescem with the Formation of Eosin (a) In a mortar grind up and intimately mix 15 grammes of phthalic anhydride with 22 grammes of resorcinol. the dyestufF salt is directly formed by the transformation. which bears the name of Brilliant Green..H 4 . this method. Vegetable fibre (cotton) is not coloured unless it has been previously mordanted.N(CH 3 ) 2 _ Cl + H . .AROMATIC SERIES 323 Further. silk and wool. diethyl aniline is used. directly. 183. The dyes of the Bitter Almond Series colour only the animal fibres. has been abandoned.C O H 4 . — the Malachite Green Series. But if zinc chloride is added.C.N(CH S ) 2 ~ *C1 Since the chlorine atom remaining over migrates toward a nitrogen atom. can be used. The salt of the formula given above is difficult to separate from its solution. a double salt of the same colour is formed: 3(C23H25N2C1) + 2 ZnCl2 + H2O which may be separated from its water solution by common salt. In place of benzaldehyde. Malachite Green may also be made by a second method. etc.. Malachite Green is a representative of a whole series of dyes. which was formerly used. in the formation of the leuco base. If. the hydrogen atom in the para position to the dimethylamido groups N(CH S ) 2 unites with the aldehyde oxygen atom to form water.1. REACTION: CONDENSATION OP PHTHALIC ANHYDRIDE WITH A PHENOL TO FORM A PHTHALEIN EXAMPLE: (a) Fluorescein. with stirring (glass rod). gradually thickens. After the mass has been kept in a fused condition for a few minutes. for which about 1-2 hours is required. As a vessel for heating the mixture. finely pulverised.324 SPECIAL PART oil-bath to 1800 (Fig. which always contains water. and the heating continued until the liquid. of water and 10 c. After adding 7 grammes of the anhydrous salt thus obtained. Yield. pour 60 grammes . 78. it can be obtained readily at a small cost. of concentrated hydrochloric acid. the temperature is increased to 2100. the addition of hydrochloric acid is necessary to dissolve the zinc oxide and basic zinc cflloride. 78). (3) Over 15 grammes offluorescei'nin a flask. This causes the solution of the substance which did not enter into the reaction. The fluorescei'n is filtered from the solution. glazed inside. in the course of 10 minutes. and boiled 10 minutes in a porcelain dish with 200 c. it is then dried on the water-bath. The cold friable melt is removed from the crucible with a sharp instrument (it is best to use a chisel). and may be used several times for the same fusion. To the fused mass add. washed with water until the filtrate no longer gives an acid reaction. almost quantitative. It is suspended by its projecting edge from a triangle into the oil-bath. is well adapted to the purpose. becomes solid. it is allowed to cool. an "extract of beef" jar. 7 grammes of pulverised zinc chloride. and the solidified substance is removed from the dish with a knife and pulverised. is carefully heated to fusion over a free flame in a porcelain dish.c.c. which FIG. This is prepared in the following way : 10 grammes of the commercial salt. and by this manipulation the disagreeable bromine vapours may be avoided (Fig. from a separating funnel. 79). it is observed that the quantity of fluorescein insoluble in alcohol steadily decreases. This is due to the fact that the dibromide is first formed. This should require about a quarter-hour. 79- FIG. by which the troublesome weighing of bromine is obviated. a clear. In the above case. of bromine are necessary. add. the one best adapted to this FIG. with frequent shaking. which is easily soluble in . it is advisable. and that when about one-half of the bromine has been added. In place of a separating funnel. since it possesses no cock. in order to find the number of cubic centimetres corresponding to the weight.c. as in all cases of bromination. purpose is the Winckler form. dark.AROMATIC SERIES 325 of alcohol (about 95 %). it is only necessary to divide the required weight by 3. 33 grammes of bromine. 80. to use a burette. 11 c. On the addition of bromine. it can be inserted into the body of a flask with a not too narrow neck. Since the specific gravity of bromine at moderate temperatures is very nearly 3. drop by drop. reddish-brown solution is formed. Of the numerous kinds of burettes. add 20 grammes of alcohol. — Over a flat-bottom crystallising dish. In order to obtain pure eosin from it. and filter the hot'solution. On the large scale. the soluble sodium salt separates out in the form of splendid. the tetra-bromide is formed. On cooling. dry ammonia evolved from ammonium chloride and lime is passed into the chest. of water. by testing a small portion with water. heat on the water-bath until the evolution of carbon dioxide ceases. — Grind 6 grammes of eosin with 1 gramme of dehydrated sodium carbonate. which forms dark-red crystals with a greenish lustre. necessary. heat to boiling. \ filled with a concentrated ammonia solution. and in a not too small beaker moisten it with a little alcohol. After the eosin is spread out on the linen in thin layers. or ammonium-salt is prepared on the large scale for dyeing. and dried on the water-bath. Since eosin is insoluble in water. since it is difficultly soluble in alcohol. Upon this is spread the eosin acid. washed several times with alcohol. 80). The end of the reaction is easily recognized. . this reaction is carried out in wooden chests containing a number of frames covered with coarse linen. Ammonium Eosin. one day. the precipitate is filtered off. and. arranged like drawers. is. its colour becomes brighter. which. after the addition of 5 c. sodium-. separates out in the form of brick-red leaflets. As is the case with many dyes. place a filter. The bright-red crystals of the free eosin acid very soon assume a darker colour. of paper as strong as possible. To the water solution of sodium eosin thus obtained. the crystallisation requires a long time. Sodium Eosin. The product thus obtained is a compound of 1 molecule of eosin and 1 molecule of alcohol. After all the bromine has been added. and the whole is covered with a funnel (Fig. in a layer about \ cm. it is completely converted into the ammonium salt. until a test-portion of the substance will completely dissolve. the soluble potassium-.c. brownish-red needles of a metallic lustre. the substance is heated a halfhour in an air-bath at n o 0 : during the heating. If it dissolves. the reaction-mixture is allowed to stand for 2 hours.326 . after about three hours. at Jesst. On the further addition of bromine. SPECIAL PART alcohol. the conversion is complete. thick. Phthalophenone is considered to be the mother-substance of the group: which. as already stated.OH HO 1 OH 1 HJ O CJVC 6 H 4 :o dioxyph th al ophenone #Phenolphthalein= For the knowledge concerning this class of compounds. is obtained from phthalyl chloride and benzene in the presence of aluminium chloride. a hypothetical mono-carbonic acid of triphenyl carbinol would result: . which unites the carbonyl groups. this action results in the formation of an anthraquinone derivative: Phenol ' Oxyanthraquinone Or (2) one molecule of the anhydride can react with two molecules of the phenol in such a way that one of the two carbonyl-oxygen atoms of the former combines with one ring-hydrogen of the two phenol molecules to form a so-called phthalem: HLC0H4.AROMATIC SERIES 327 Phthalic anhydride and phenols can react with each other in two different ways. can combine with two ring-hydrogen atoms of the phenol to form one molecule of water. to which belong numerous important dyestuffs. we are indebted to the investigations of A. (1) An equal number of molecules of each can condense. the oxygen atom of the anhydride. If one conceives that the mother-substance can take up one molecule of water. Baeyer (1871). colourless in the free condition. discovered in 1874 by Caro. The four bromine atoms are equally divided between the two resorcinol residues: HO 206 C O OH which follows from the fact that eosin in fusion with potassium hydroxide yields di-bromresorcinol besides phthalic acid. X)H Fluorescein Fluorescein is technically prepared on the large scale by the method given above. the formation ot a tetraoxyphthalophowne would naturally be expected.328 SPECIAL PART the formula of which shows very clearly the connection between the phthaleins and the triphenyl methane derivatives. Instead of phthalic anhydride. the di. is obtained. A number of its halogenand nitro-substitution products have valuable colouring properties. containing the constituents of one molecule of water less than this. phenolphthaleiin is obtained. in spite of the intense colour of its salts. phthalic anhydride is allowed to act on phenol. CfiH. as expressed by the above equation.and tetra-chlor-substitution products are fused with . but fluorescein. is not a dye. its salts are red. in that it does not colour fibres. an inner anhydride formation taking place between the two hydroxyl groups: HO OH -f 2H 2 O. But it is not manufactured as a dye. By the action of phthalic anhydride on resorcinol. The simplest dye of this kind is eosin or tetrabrom-rluorescein. If. While phenolphthalem. since it has been replaced by other dyes that give as beautiful colours and are cheaper. It is used as an indicator in volumetric analysis. fluorescein is a true dye which colours animal fibres a fast yellow. a substance of acid properties. and are prepared from it. and tetra-chlorfluoresceins from which halogen substitution products. or amidophenols substituted by alkyls in the amido-group. and so there is obtained in the phthalic acid residue. This is done by heating phthalic anhydride with the 7/-trioxybenzene — pyrogallol. Since 1887 the phthaleins have been on the market under the name of rhodamines. CcHf _ / • /NH 2 lOHl H. C NH2 CO +2H 2 O. but there is a simultaneous splitting off of the hydrogen atoms of two hydroxyl groups resulting in a peroxide union: CGH From gallein. is obtained by heating with sulphuric acid. Rose Bengal). etc..N NHo c 0 CflH >0 CO + H. the di. are used: H . ethers. are prepared on the large scale (Phloxine. Gallein.In this case the same anhydride formation takes place as in the preparation of fluoresce'in. except that instead of resorcinol.AROMATIC SERIES 329 resorcinol on the large scale. m-amidophenol. nitro-derivatives. . a derivative of anthracene. a new dye. ccerulem. which are prepared in a manner similar to that of fluorescem. Simplest Rhodamine The rhodamine on the market is the tetra-ethyl derivative of this mother-substance. Besides fluorescem there is practically only one other phthalem prepared technically. this operation is repeated until the substance has been almost entirely dissolved. the latter is boiled again with a fresh quantity of dilute hydrochloric acid. On cooling. + H. The blue solution is filtered while hot from the colour-base. the solution of the dye is treated with finely pulverised salt (stirring) until the dye is precipitated. washed with water. 10 grammes of Michler's ketone (this is on the market). and 10 grammes of phosphorus oxychloride. in accordance with the following equation: C6H4. The blue-coloured mass is then poured into water. the Crystal Violet separates out in coarse crystals of a greenish colour. 5 hours. If Michler's ketone is heated with an amine in the presence of a condensation agent (phosphorus oxychloride. addition takes place.33O SPECIAL PART 42. which remains undissolved. and treated with steam until no drops of the unattacked dimethyl aniline pass over. and boiled with a mixture of 1 litre of water and 5 grammes of concentrated hydrochloric acid. and crystallised from a little water. After cooling. POC13).N(CH3)2 CO C 6 H r N(CH 3 ) 2 Michler's ketooc Q ^ N(CH3). on an actively boiling water-bath. pressed out on a porous plate. is heated in an open.C6H4. these are filtered off and dried in the air on filter-paper. dry flask.N((M3)2=d<^ OH Hexamethylpararosaniline » Ctoyr-base of £rystal Violet . After cooling. the solidified colourbase remaining in the distillation flask is filtered from the alkaline solution. made alkaline with a solution of caustic soda. REACTION: CONDENSATION OF MICHLER'S KETONE WITH AN AMINE TO A DYE OP THE FITCHSINE SERIES EXAMPLE: Crystal Violet from Michler's Ketone and Dimethyl Aniline A mixture of 25 grammes of dimethyl aniline. It is then filtered with suction. NH 2 C^C 6 H 4 . Dyes can also be prepared in the same way by the combination of other amines with Michler's ketone. as in the formation of Malachite Green. REACTION: CONDENSATION OP PHTHALIC ANHYDRIDE WITH A PHENOL TO AN ANTHRAQUINONE DERIVATIVE EXAMPLE : Quinizarin from Phthalic Anhydride and Hydroquinonel A mixture of 5 grammes of pure hydroquinone and 20 grammes of phthalic anhydride is heated in an open flask 'with a mixture of 100 grammes of pure concentrated sulphuric acid and %o IB.NH 2 !2 :6H4.N(CH ) 6 4 3 2 /CeH4-N(CHa)a Cs-C G H 4 . one molecule of this is added.NH 2 ^C 6 H 4 =NH 2 indeed. . It is prepared technically in the same way.p. . and forms the principal constituent of the Methyl Violet obtained by the oxidation of dimethyl aniline.NH2C1 or 7 C 6 H 4 .N(CH 3 ) 2 ||\C 4 H . 312.N(CH 3 ) 2 C1 HC/\CH Hcl C JCH = Quinoide formula. i$9. 506. and.N(CH 3 ) 2 X C 6 H 4 . it may be considered as a hexamethyl parafuchsine.AROMATIC SERIES 331 If this is dissolved in hydrochloric acid. 43. 6. the elimination of a molecule of water immediately takes place and the dye is formed: X 6 H 4 . 5. A. of which it is only possible to mention here Victoria Blue and Night Blue. ' Crystal Violet It is a derivative of parafuchsine: : 6 H 4 . 1 NTO' Quinizarin In an analogous way.(OH) 2 = C 6 H / > C C H 2 ( O H ) 2 + H 2 O.c. on cooling. and is driven over as rapidly as possible with a large flame. The hot solution is poured. to form derivatives of anthraquinone. it has already been mentioned that phthalic anhydride condenses with phenols in certain proportions. A beaker is used as a receiver. alizarin is . It is of theoretical importance that from pyrocatechol (o-dioxybenzene). after filtering. besides a second isomer. Since it is difficult to obtain it pure by crystallisation. The directions as to time and temperature must be followed as exactly as possible. the filtrate poured into a beaker. into about 400 c. while hot. On cooling of the diluted acetic acid solution. and. combine with phthalic anhydride. treated with its own volume of hot water. which is steadily diluted with water. of water in a porcelain dish. after drying it is distilled from a small retort of difficultly fusible glass. dried first on the water-bath. from which. orange-yellow leaves.|C 6 H 2 . The reaction just effected takes place in accordance with the following equation: JO+H 2 . until finally only pure water is used. these are filtered off and washed with glacial acetic acid. the crude quinizarin separating out is filtered off. The residue remaining on the filter is again boiled up with 100 c.332 SPECIAL PART grammes of water for 3 hours in an oil-bath to 170-180 0 . it is crystallised from glacial acetic acid. and. of glacial acetic acid. Under the preparation of fluorescein. and finally in an air-bath at 1200.as well as poly-acid phenols. heated to boiling.c. filtered hot with suction. washed with water several times. and finally for 1 hour at 190-2000. The residue remaining on the filter is again boiled out with water and filtered while hot.c. glacial acetic acid. mono-acid. In order to separate the quinizarin from carbonaceous decomposition products. and filtered hot with the aid of a Btichner funnel. treated as above. with stirring. the precipitate is boiled with 200 c. the quinizarin separates out in the form of large. After the distillate in the receiver and that in the neck of the retort (this is broken) has been finely pulverised. 359. for 20 hours to 1700. heat a mixture of 10 parts commercial sodium anthraquinonemonosulphonate. Spl. .8 parts of finely pulverised potassium chlorate. B. like oxyanthraquinones. In order to obtain it completely pure.AROMATIC SERIES 333 obtained.) Since it does not contain the hydroxyl groups in the vicinal a-/?-positions.QH . 300. similar compounds are also obtained: CO \C C H. either with suction or with the aid of a filter-press. the melt is boiled out with water several times.(0H)3+2H2O Anthragallol Quinizarin dissolves. showing that the two hydroxyl groups in alizarin are in the ortho position to each other. in alkalies with a violet colouration.(OH) 3 =C 6 H/ Benzo'ic acid Gallic acid >CCH.(OH)3 = Pyrogallol Trioxyanthraquinone = Anthragallol It may be mentioned briefly that by the condensation of benzoic acid with oxybenzo'ic acids. This will be explained further under Alizarin. 4 4 . pressed out on a porous plate. and acidified at the boilingpoint of the solution in a large dish with concentrated hydrochloric acid. 30 parts of sodium hydroxide. it will not form dyes with metallicsalt mordants. and is 1 A. 9. After cooling. washed with water. which is obtained on the large scale by heating pyrogallol with phthalic anhydride: . . it is distilled rapidly from a small retort. The alizarin separating out is then filtered off according to the quantity. REACTION: ALIZARIN FROM SODIUM P-ANTHRAQUINONEMONOSUI/PHONATE i In an autoclave or an iron pipe with a cap which can be screwed on (see page 64). and dried in an air-bath at 1200. (Try it. 7. Of practical significance is the above reaction for the preparation of anthragallol.3. 1. 281. with 40 parts of water. On the large scale the alizarin fusion is conducted exactly as on the small scale. With alizarin and all its related compounds dyeing is effected by mordanting the fibre with a salt of one of the imthe the . It is oxidised by chromic acid to anthraquinone (see below). except that autoclaves. this is obtained from the highest-boiling fractions of coal tar (anthracene oil). the reaction being effected in air. on account of its silvery appearance. or in large quantities from nitrobenzene. and the garnet-brown chromic salt are especially portant in dyeing. are used. violet ferric salt. the sodium anthraquinonemonosulphonate is precipitated directly. it is formed with the evolution of hydrogen. which thus obviates the necessity of removing the excess of sulphuric acid beforehand. The red aluminium salt. a hydrogen atom is also oxidised to a hydroxyl group: XXX /H C6H4< >C6H/ + 3 NaOH + O \CO/ \SOoNa O X)Na \ONa 6H2< The tendency to the formation of alizarin is so great that even without the addition of an oxidising agent (potassium chlorate or nitrate). is called "Silver salt. anthracene is the starting-point. and this on heating with sulphuric acid is converted into the monosulphuric acid. The constitutional formula of alizarin is: OH CO :o The salts are intensely coloured. The separation of this latter compound is greatly facilitated by the fact that it forms a sodium salt difficultly soluble in water. Formerly the oxygen of the air was used as the oxidising agent. with stirring attachments. The sodium hydroxide fusion of the sodium anthraquinonemonosulphonate is an abnormal reaction to the extent that besides the replacement of the sulphonic acid group by hydroxyl. which. In order to prepare alizarin on the large scale.334 SPECIAL PART crystallised from glacial acetic acid.17 If the sulphonation mixture is diluted with water and neutralised with sodium carbonate. and finally. whereby salts are formed on the fibre (Lakes). by heating with glycerol and sulphuric acid. the thus prepared fibre is heated with a thin dilute water-paste of the free insoluble dye. REACTION: ZINC DUST DISTILLATION EXAMPLE : Anthracene from Alizarin or Quinizarin To a paste prepared by rubbing up 100 grammes of zinc dust with 30 c. the derivatives of alizarin (Rule of Liebermann and Kostanecki). 45. A combustion tube of hard glass 60-70 cm. From alizarin there can be prepared. add pieces of porous pumice stone of a size that will conveniently pass into a combustion tube. and from this. are prepared in a manner analogous to that by which alizarin is obtained from the monosulphonic acid. They are removed from the paste with pincers. etc. but with metallic oxides it forms no salts on fibres. by the action of fuming sulphuric acid on alizarin there is obtained a tetraoxyanthraquinone (Bordeaux). of water. Further. and stir them around so that they become covered with the zinc dust paste.and amido-alizarin. long is drawn out at one end to a narrow tube. long. two trioxyanthraquinones. and dry hydrogen . long is placed next to the plug. The above prepared quinizarin dissolves in alkalies with a violet colouration.and poly-oxyanthraquinones only those are actual dyes which contain. two hydroxyl groups in the vicinal a-jG-position. the tube is transferred to a combustion furnace inclined at an oblique angle.and anthra-purpurin.or /?-nitro-alizarin.AROMATIC SERIES 335 three oxides just mentioned. i. like alizarin. flavo.c. and a layer of zinc dust 5 cm. From two disulphonic acids of anthraquinone. After a canal has been formed over the zinc dust. heated in a porcelain dish over a free flame (in.e. From /?-nitro. a layer of pumice-zinc dust 30 cm.constant motion) until the water is evaporated. the important Alizarin Blue is obtained. by reduction. by placing the tube in a horizontal position and tapping it. the corresponding amidoalizarin. the narrowed end is closed by a loose plug of asbestos. by nitration. further. then follows a mixture of ^-1 gramme of alizarin or quinizarin with 10 grammes of zinc dust. the a. Of the numerous di. the gas being evolved is conducted into a soap solution.1 When this is the case. The anthracene formed condenses to crystals in the forward cool part of the tube. the air has not been completely removed. the test may also be made by filling a test-tube with the gas over water. After the reaction is complete. and as soon as this glows. of zinc dust is similarly heated. it is heated as strongly as possible. the mixture of the substance and zinc dust is gradually heated. are thus obtained. 2130. The sublimed anthracene is dissolved by heating in a testtube with a little glacial acetic acid. and heated a short time to boiling. Melting-point. the current of gas is diminished so that only two bubbles per second pass through the wash-bottle. while the tube is allowed to cool. If an explosion accompanied by a report takes place when the bubbles are ignited. 1 As described under Carbon Monoxide. these are increased in size gradually. and is finally crystallised in a test-tube from a little glacial acetic acid. In order to test whether the air has been completely expelled from the tube. then only pure hydrogen is present. it is treated with about double its weight of chromic anhydride.336 SPECIAL PART is passed through the tube without heating. the forward part of the tube containing the anthracene is broken off and the substance removed with a small spatula. it is purified by sublimation in a suitable apparatus (see pages 14 and 15). a moderately rapid current of hydrogen is passed through it. otherwise a serious explosion may result. washed with some dilute sulphuric acid. and the bubbles formed are ignited. as in the nitrogen determination. but if they burn quietly. and applying a match to the. the pumice-zinc dust is then heated with small flames. then with water. the anthraquinone separating out is filtered off. then the rear layer of 5 cm. the open end is closed by a cork bearing a small glass tube to which is attached a piece of rubber tubing. and finally. during which the greatest care must be taken to keep the flame from coming in contact with the gas issuing from the rubber tubing. the tiles being placed in position. . mouth of the tube. which melt at 2770. The solution is then diluted with several times its volume of water. Long colourless needles of anthraquinone. ) III. 140. 1. REACTION: THE PYRIDINE SYNTHESIS OF HANTZSCH* EXAMPLE : Collidine = Trimethylpyridine Dihydrocollidinedicarbonic Acid Ester. and allowed 1 A. which can be used for the reduction of almost all aromatic oxygen compounds derived from hydrocarbons. since. A. OH + Zn = C0Hfl -I.g. e. The warm reaction-mixture is then treated with double its volume of dilute hydrochloric acid. or by warming on the water-bath. — A mixture of 25 grammes of acetacetic ester and 8 grammes of aldehyde-ammonia is heated in a small beaker on a wire-gauze. by means of it. The reaction given under Alizarin possesses an historical interest. can be replaced by hydrogen. (B. z . discovered that alizarin. especially at high temperatures. about three minutes. an excellent reducing agent (Baeyer. either by pressing out. and stirred vigorously without further heating until the liquid mass solidifies. as the above example shows. OH + Zn = C 10 H 8 + ZnO Also ketone-oxygen. 43. 295). SERIES 1. in 1868. 2 grammes of the crude product are dissolved in a small quantity of alcohol in a test-tube. washed with water. which had been previously obtained from madder root. filtered.ZnO Phenol Naphthol Benzene Naphthalene C 1 0 H 7 . In order to obtain the dihydroester in a crystallised condition.PYRIDINE SERIES 337 Zinc dust is. to IOO-IIO 0 . PYRIDINE OR QUINOLINE. the crude product can be directly used. 215. It is then thoroughly triturated in a mortar. For the further working up of the collidinedicarbonic acid ester.1. Grabe and Liebermann. was a derivative of anthracene. by heat. the mixture being stirred with the thermometer. and dried.: CG H 6 . and could be prepared synthetically from it. the potassium salt separates out in crusts. on account of the high boiling-point of the ester. or potash. and heated 4-5 hours on a rapidly boiling waterbath (with reflux condenser) . rating out is taken up with ether. Colourless tablets with a bluish fluorescence are thus obtained. and the residue subjected to distillation. prepared in the following manner : Finely pulverised potassium hydroxide (2 parts to 1 part of ester) is moderately heated in a flask on a wire-gauze with 3 times its weight of absolute alcohol. complete solution does not take place. — The saponification of the ester is effected by boiling with alcoholic potash. having the condensation tube as near as possible to the bulb. until the greater portion has passed into solution. After the ethereal solution has been dried by a small piece of potassium hydroxide. until the dihydroester goes into solution. The alcohol is then evaporated by heating on the water-bath.338 SPECIAL PART to cool slowly. — The crude dihydroester is treated in a small flask with an equal weight of alcohol. 81). The fraction passing over between 290-3io° can be used for the following experiment: Potassium Collidine Bicarbonate. treated with the ester to be saponified. and the latter washed on the filter with alcohol and finally with ether- . the oil sepa. Collidinedicarbonic Acid Ester. the ether is evaporated. the thick residue is treated with a sodium carbonate solution to alkaline reaction. The alcoholic solution is then poured off from the portion remaining undissolved. The alcoholic liquid is then 'poured off from the salt. Melting-point. a fractionating flask is selected. 81. 1310. Into the mixture cooled by water pass nitrous fumes (Fig. and a test-portion dissolves to a clear solution in dilute hydrochloric acid. I n order to prevent the mixture from being carried over into the receiver on heating.PYRIDINE SERIES 339 Collidine.CO /CH\ CH2. the rear end of which is somewhat elevated and warmed throughout its entire length with small flames. 215. it is then transferred to a combustion furnace. OC—CH2 CHj—CO NH 2 H CO-CH8 y CH 2 —CO.C || CH 8 —C X C. a n d ammonia. the tube is heated as strongly as possible. the tube is connected with an adapter bent downwards. On heating acetacetic ester with aldehyde-ammonia. OC—C H8C-C \ \.OC. wide and 55 cm. the dihydrophenyllutidinedicarbonic ester: C6H6 . OC2H N H N H C—CH8 / . by means of a cork or asbestos paper. the following reaction takes place (see A.OC. acetacetic ester.OC2H5 = I CO. a small. and placed in one end of a hard glass tube (about 2 cm. OCH . dried with potassium hydroxide. OC 2 H 6 = QH5O. Dihydrocollidinedicarbonicethyl ester T h e reaction may be modified by using other aldehydes instead of acetaldehyde. with the tiles in position. The flames are steadily increased in size until.CO.CHS C2H5O. long). — The dried potassium salt is intimately mixed in a mortar with double its weight of slaked lime. C—CO. after the evaporation of the ether. thus there is obtained from benzaldehyde.OC 2 H 6 || C—CIIs \XT/ HNH2 N II +3II2O. loose plug of asbestos is placed in the tube in front of it. beginning at the closed end. is subjected to distillation. Boiling-point.CO.CH2 I CH 8 . and. 8) : CH8 I OCH C2H5O. 172 0 . After a canal has been made by tapping. The collidine passing over is taken up with ether. REACTION: SKRATJP'S QinNOLENTE SYNTHESIS EXAMPLE: Quinoline In a flask of about i£ litres capacity containing a mixture of 24 grammes of nitrobenzene. Calcium benzoate (ca=|Ca) In poly-basic acids. and 120^ grammes of glycerol. wide reflux condenser. While the dihydroesters possess no basic properties. In the above case. respectively. 2.g. The splitting off of carbon dioxide from a carbonic acid. and there is formed a derivative of pyridine. butyraldehyde.: C fi H. valeraldehyde. the reaction can be carried out. 38 grammes of aniline. and others. and heated on the sand-bath. by treating the solution with hydrochloric acid. two hydrogen atoms. Therefore. with stirring.lC00ca + ca0|H = C6H6 + CaCO>8. will be oxidised off. phenylacetaldehyde. the pyridine derivative dissolves in acid. By passing nitrous fumes into an alcoholic solution of the dihydroester. refer to what was said under Reaction 36. all the carboxyl groups can be replaced by hydrogen. depending upon the nature of the aldehyde employed. e." For this kind of action a calcium salt is most frequently used. As soon .and imidogroups. The flask is then connected with a long. 100 grammes of concentrated sulphuric acid.34O SPECIAL PART With proprionic aldehyde. All the compounds obtained contain the methyl groups of the two acetacetic ester molecules. is generally designated as a " pyro-reaction. furfurol. cenanthol. and those particular hydrogen atoms in combination with carbon and nitrogen in the methenyl. add. nitrobenzaldehyde. this is mixed "with slaked lime and subjected to distillation. In this way an acid may be transformed into the hydrocarbon from which it was derived. Concerning the saponification of the ester.. or a salt of a carbonic acid. but the third side-chain is different. the potassium salt may be used instead of the calcium salt. it can be determined whether any unchanged dihydroester (insoluble in acid) is present. containing no ring hydrogen. myristic aldehyde. 2370. mixed with the unchanged aniline. by which. Since these substances cannot be separated by fractional distillation. the distillation with steam is discontinued. and from the acid liquid the unchanged nitrobenzene is removed with steam.) Quinoline is formed in the above reaction according to the following equation: H CH2. if the blue colour does not appear. their separation must be effected by a chemical method. diluted with water. as in Reaction 8. (See Wiener Monatshefte 2. and the energetic reaction is allowed to complete itself without further heating from without. while the tertiary quinoline remains unchanged. Yield. When the reactionmixture has become quiet. and then made alkaline with concentrated caustic soda solution.OH . 141. while the quinoline is liberated. upon which the phenol goes into solution. the flame is removed. upon which the liberated quinoline. For this purpose the distillate (oil and water solution) is treated with dilute sulphuric acid until all oil is dissolved and an excess of the acid is present. to the cold solution a solution of sodium nitrite is added until a drop of the liquid will cause a blue spot on potassium iodide-starch paper. The aniline (primary amine) is converted into diazobenzenesulphate. The mixture is now distilled with steam. The mixture is heated for some time on the waterbath. add more sulphuric acid to the mixture. it is again heated for three hours on the sand-bath. and the quinoline is obtained in a pure condition: it is taken up with ether. the ether evaporated. is distilled over with steam.QUINOLINE SERIES 341 as the reaction begins. which is recognised by the sudden evolution of bubbles of vapour ascending through the liquid. the diazo-sulphate is converted into phenol. As soon as no drops of oil pass over. The liquid is again made alkaline. Boiling-point. The liquid remaining in the distillation flask is allowed to cool somewhat. 40-45 grammes. and the residue distilled. . connected with the benzene ring. CH=CH 2 = C6H5. which is hereby reduced in a manner that is not wholly clear. are obtained.or oxy-derivatives of quinoline. C6H5. yields a blue dye. under the influence of sulphuric acid: CH2. Also halogen-. methyl-.OH CH2 +2H2O. N=CH—CH=CH 2 + H 2 O. etc. amidophenols. acrole'in is formed from glycerol. dimethyl-aniline. this condenses with aniline to form acrolemaniline. By starting from the diamines. substituted quinolines. This gave the impetus to Skraup's synthesis. yield halogen-. that /?-nitroalizarin. If. substituted amines. etc. the corresponding quinoline is obtained. nitro-. The reaction is also applicable to the corresponding amido-compounds of the naphthalene series. yield carbonic acid-. sulphonic acid. are formed.. To Grabe's investigations we are indebted for the knowledge of the process by which. Quinoline The Skraup reaction is capable of a very many-sided application.OH = C H CH2. Alizarin Blue.. amidosulphonic acids. loses two atoms of hydrogen. its homologues are used. in this way the so-called phenanthrolines. as above. a quinoline synthesis is effected in the following way: . under the influence of the oxidising action of the nitrocompound. etc. It is possible that the reaction may take place in this way: first. instead of aniline. Amidocarbonic acids. NH2 + CHO. etc. Of technical and historical interest is the discovery which was made by Prudhomme in the year 1877. and thus quinoline is formed: H2O. two new pyridine rings. CH. While this.OH CHO Like all aldehydes.342 SPECIAL PART The oxygen ne-essary for the reaction is taken from the nitrobenzene. on heating with glycerol and sulphuric acid. nitro-. to this is added a quantity of concentrated hydrochloric acid which is just sufficient to cover it.HYDROCHLORIC ACID OH 343 Nitroalizarin Residue of the glycerol added Alizarin Blue IV. INORGANIC PART I . this is passed through two washbottles containing water and concentrated sulphuric acid respectively. the water retains any hydrochloric acid which is carried along with the gas. 2. as is always done on heating large flasks. and the sulphuric acid dries it. which is frequently needed for the preparation of acid-esters. CHLORINE A flask is one^ third filled with manganese dioxide (pyrolusite) in pieces the size of filberts. HYDROCHLORIC ACE) Gaseous hydrochloric acid. a regular current of chlorine is generated. is generated most conveniently in a . A very regular current of chlorine can also be obtained from finely pulverised potassium dichromate and crude concentrated hydrochloric acid by heating the mixture on the water-bath. To 1 litre of hydrochloric acid. by which the danger of breaking is essentially diminished. (See Figs. 74 and 87. On heating the mixture on a wire gauze with a free flame. use 180-200 grammes of pulverised potassium dichromate.) A piece of thin asbestos-paper is placed on the wire gauze. bent at a right angle. 82). the acid can be generated very conveniently in the following manner: In concentrated hydrochloric acid contained in a suction flask allow to flow from a separating funnel concentrated sulphuric acid. The operation is conducted in the same way as that for the generation of carbon dioxide or hydrogen from a Kipp apparatus. thus relieving . through this insert a narrow delivery tube. with an irregular gas current.344 SPECIAL PART Kipp apparatus charged with fused ammonium chloride in pieces as large as possible. the liquid to be saturated may be easily drawn back into the wash-bottle and then into the generating mixture. The liquid to be saturated cannot flow back into the washbottle with this arrangement. which reaches almost to the bottom of the bottle. 84): Into a two-hole cork place a straight tube as wide as possible. FIG. since otherwise. 83. and concentrated sulphuric acid. this latter is always used. safety wash-bottle (Fig. If the apparatus is not available. a single-neck wash-bottle may be converted into a safetybottle as follows (see Fig. 83) . since in case there should be a tendency to do so. 82. In place of a Woulff-flask with three tubulures. air would enter the suction-flask through the space between the delivery tube and the wider tube. drop by drop (Fig. The hydrochloric acid evolved is dried by passing it through concentrated sulphuric acid contained in a FIG. c. capacity (Fig. To 1 part of hydrobromic acid 0. The water solution of the potassium bromide is evaporated to dryness on a water-bath. . it can also be converted into a safety-tube (see Fig. when a 48 % acid goes over. 85). 3. 4. 86). 85. The product thus obtained may be used directly for the preparation of ethyl bromide. Water first passes over until finally the temperature remains constant at 126°.5 part potassium carbonate is used. If a wash-bottle having a side-tube is available.HYDROBROMIC ACID 345 the pressure. In order to prepare potassium bromide for use in the preparation of ethyl bromide. this is collected. gradually add 4 grammes of yellow phosphorus divided into about 8 pieces. FIG. HYDROBROMIC ACID (see Brombenzene) The hydrobromic acid obtained as a by-product in the bromination reactions is purified by distilling it from a fractionating flask. HYDRIOIHC ACID To 44 grammes of iodine (not pulverised) contained in a small round flask of about 100 c. the acid is diluted with some water and then treated with dry potash until there is no further evolution of carbon dioxide and the liquid shows a neutral reaction. FIG. Hydrochloric acid gas may also be obtained by warming 10 parts of sodium chloride with a cold mixture of 3 parts of water and 18 parts of concentrated sulphuric acid. 84. under certain conditions the water may be drawn back. In this is placed glass FIG. since otherwise the flask may be easily broken. above the surface. which soon become liquid. The contents of the flask steadily become clearer. Proceed as follows : 5 grammes of red phosphorus are rubbed up to a paste with 2 ex.c. The reaction still proceeds with evident energy. at the 1 most). but its end must be 1 cm. otherwise. which on stirring around in the mixture become covered with the paste. while in the other flask the heavy layer . a fused.c. In order to prepare a water solution of hydriodic acid. When the first action is ended. The hydriodic acid is now obtained by treating the co?7ipletely cooled phosphorus triiodide with 6 grammes of water and warming with a very small luminous flame. of a water solution of hydriodic acid. or bits of broken glass. must be passed over red phosphorus in order to free it from iodine which is carried along with it. in consequence of the great affinity of water for hydriodic acid. with as little water as possible (i c. The first piece of phosphorus added unites with the iodine with an active evolution of heat and light. the gas issuing from the U-tube is passed into 45 c. 86. after shaking the contents of the flask. of water (see Fig. Care is taken to place the phosphorus as nearly as possible in the middle of the flask. dark mass of phosphorus triiodide is obtained which becomes solid on cooling. the second piece is added. by pressing between layers of blotting-paper. although it is less intense than when the first piece was added.346 SPECIAL PART these are dried just before transferring them to the flask. or in case this is not available. and not to allow it to fall on the walls. The glass tube is not immersed in the water. When all of the phosphorus is added. The hydriodic acid prepared from this by warming with water. beads. They are then transferred to a U-tube. 86). to pass over to the highest oxidation product — phosphoric acid. colourless liquid remains in the generating flask. which is evolved. At first a few cubic centimetres of water pass over at ioo°. The heating is continued until only a clear. PH 4 I. with the evolution of phosphine on heating. First. In order to obtain a concentrated solution of hydriodic acid. the liquid in the receiver is distilled. to form hydriodic acid. boiling constantly at 1270. with hydriodic acid. In this experiment it is observed that the connecting tubes of . especially those between the generating flask and the U-tube become coated with crystals of a diamond-like brilliancy.HYDRIODIC ACID 347 of hydriodic acid sinks to the bottom. since it possesses weak basic properties. This experiment teaches much concerning the chemistry of phosphorus and iodine. the reaction takes place as follows: The phosphine thus formed unites. while the phosphorous acid (H 3 PO 3 ) remains in the flask: The gaseous hydriodic acid is an intensely fuming substance. Hydriodic acid is absorbed by water with great avidity. the concentrated acid passing over up to 1300 is collected separately. The acid. it shows that iodine and phosphorus unite directly with a vigorous reaction. These are crystals of phosphonium iodide. to form phosphorus triiodide: The iodide then decomposes with water. to form phosphonium iodide: . With phosphorous acid. This boils for the most part at 12 f. then the temperature rises in a short time to 125 0 . which may be easily shown by removing the cork from the receiver containing the aqueous acid. the apparatus. which is formed by the decomposition of phosphorous acid. contains approximately 50% of anhydrous hydriodic acid. It is a common property of all the lower oxidation products of phosphorus. for a moment. (See Fig. This reaction. care being taken to prevent it from becoming ignited by friction in the opening of the tubulure. 5. with a knife or chisel.348 SPECIAL PART ' Since this may easily clog the connecting tubes. in accordance with this equation: PH41 + H8O = PH. and heated gently on a wire gauze with a free flame (under the hood). On cleaning the tubes with water. is employed. in a porcelain mortar. an empty wash-bottle. retort.) 7. and which in this case is not spontaneously inflammable. cut 40 grammes of yellow phosphorus. AMMONIA Gaseous ammonia is prepared most conveniently by heating the most concentrated ammonia solution in a flask over a wire gauze with a small flame. a gas with a garlic-like odour.3. cooled by cold water. 87). each single piece of phosphorus is taken from the water by pincers. In order to condense the nitric acid carried along with the gases. After the air in the retort has been displaced by dry carbon dioxide (Fig. As soon as all the phosphorus has been transferred . PHOSPHORUS TRICHLORIDE Under water. 1. + H I . this reacts with the phosphonium iodide with the evolution of phosphine. sp. into pieces which will conveniently pass into the tubulure of a 300 c.c. the tubes selected are as wide as possible. NITROUS ACID For the preparation of gaseous nitrous acid. 66. (See Fig. arsenious acid. The phosphonium iodide decomposes with water into its components. gr. and dried quickly by pressing it between several' layers of filterpaper. and immediately placed in the retort.) 6. it is passed through a drying tower filled with soda-lime. In order to dry the gas. broken into pieces the size of a pea. is treated with nitric acid. is employed for preparing pure phosphine which is not spontaneously inflammable. as is well known. 81. the tubulure is connected with a delivery tube which must move easily in the cork.PHOSPHORUS TRICHLORIDE 349 to the retort. and a moderately rapid current of dry chlorine passed over the phosphorus. If crystals of phosphorus pentachloride should collect in the neck of the retort. the . phosphorus chloride is thus formed with evolution of heat and light. this is firmly connected with the end of the condenser. Ch. pr. phosphorus distils to the upper part of the retort. During the addition. A suction-flask is used as a receiver. but if this does happen. no reaction takes place. on the other hand. the phosphorus oxychloride formed is distilled. 8. 100-110 grammes. Boiling-point. by means of a cork. in small portions of about 2-3 grammes. or with a luminous flame. If. The phosphorus trichloride condensing in the receiver is distilled from a dry fractionating flask. The distillate is rectified from a fractionating flask provided with a thermometer. which * J. After each addition. 9. to 130°. 88. M Vol. the tube is somewhat raised. If. After all of the chlorate has been added. no liquid should distil into the receiver. it is started by a gentle warming. PHOSPHORUS PENTACHLORIDE Through the upper delivery tube of an apparatus similar to that represented in Fig. a stream of dry chlorine is admitted. add gradually.382. Boiling-point. wait until the liquid bubbles up. 88. 1883. by heating the retort in an oil-bath. contained in a large tubulated retort connected with a condenser. FIG. Yield. on the addition of the first portion. it is poured back into the retort. . 32 grammes of finely pulverised potassium chlorate. 1 ic°. 740. before adding a new quantity.350 SPECIAL PART delivery tube is pushed somewhat farther into the retort. Yield. PHOSPHORUS OXYCHLORIDEi To 100 grammes of phosphorus trichloride. 28. 125-140 grammes. of water and concentrated sulphuric acid. it is FIG.SULPHUROUS ACID 351 passes out of the lower. 10. an apparatus similar to that represented in Fig. as soon as it is evident that the union is completed. it can be cut into scales with a knife. 89. by volume. the end of which is wrapped in filter-paper. into which the scales fall. or pressed out into a wire with a sodium-press. From time to time. the tube is correspondingly raised. After both sides of the knife and the front part of the table have been coated with a thin layer of vaseline. several cubic centimetres of phosphorus trichloride are allowed to flow into the bottle from a separating funnel. Yield. Should the delivery tube become stopped up. upon which the trichloride unites with the chlorine to form the solid pentachloride. 11. 82. by adding to a concentrated water solution of sodium hydrogen sulphite a cold mixture of equal parts. any desired quantity of phosphorus pentachloride can be prepared. right-angled tube. SULPHUROUS ACID Gaseous sulphurous acid is generated in an apparatus similar to the one represented in Fig. As the quantity of the pentachloride formed increases. is placed on the table so that it projects somewhat over the front end. Since this operation can be repeated. a short stroke of the tnen cut ^ h knife. The generating flask is shaken frequently. it is cleared by the glass rod with which the apparatus is provided. to keep the contents from separating into layers. quantitative. On the front part of the lower platform is place'd a small dish filled with ether or ligroin. drop by drop. in order that it may be handled. a long stick of the metal to be cut. To cut it into scales. When . — In order to divide sodium into small portions. SODIUM (a) To cut Sodium. 89 is convenient. in rather rapid succession.352 SPECIAL PART using the knife.. Quadratic scales. Further. The scales are speared on the glass rod (under the hood. 90). the size of a half bean. with gloves). eyes protected by spectacles . by means of a short. which have been previously freed from oil by boiling with alcohol and then dried in an air-bath at 120°^ an asbestos plug is placed at each end of the layer. is at one end connected by means of a cork with a wide-neck so-called "salt bottle" (Fig. is passed . are cut. The mercury may also be warmed in a porcelain casserole on the water-bath (60-70 0 ). bearing a delivery tube of at least 8 mm. A rapid current of hydrochloric acid gas. extending to the centre of the receiver. large quantities of the metal can be cut in very thin scales in a short time. the cross-section of the piece of sodium must not be too large. otherwise the metal adheres to the knife. moderately thick glass rod. long. The cork with which this is closed is supplied with a second. With a little practice. most conveniently obtained from a Kipp apparatus charged with fused ammonium chloride and concentrated sulphuric acid. be more than 5-6 mm. about the size of a 20-cent piece. hands. drawn out to a point and bent at a short right angle. ALUMINIUM CHLORIDE A wide tube. The sodium residues are not thrown into water nor into wastejars. small pieces of sodium. are pressed to the bottom of mercury contained in a porcelain mortar. diameter. two points are to be especially observed. Only in this way can a wound be prevented. smaller hole. (3) Sodium Amalgam. but are dropped into alcohol contained in a beaker or flask. but always behind it. and. without further heating. are thrust to the bottom of the vessel with the aid of a glass rod. so that the fingers holding the sodium can always be seen. of hard glass drawn out to a narrow tube. 12. The eye is never placed in front of the knife. at most. diameter i£-2 cm. The tube is half filled (half of its cross-section) with aluminium shavings. the edge of which must not. — Sodium scales. alphuric acid is not too small. the flames must be immediately lowered. One should not be able to count single bubbles of the gas. an explosion of oxygen and hydrogen may take place. (5) The hydrochloric acid current -tnust be extremely rapid. For the success of the preparation. otherwise. since. which results in a stopping up of the apparatus. Care must be taken that the drying flask containing . When the flames have reached a certain size. the following points are particularly observed: (1) All parts of the apparatus must be perfectly dry. dark-coloured resi- itmtitu FIG. except for a small. 90). condensing in the receiver. 90. provided with a circular hole in the centre. at first with small flames. (2) The air must be removed as completely as possible. and the gas tested from time to time by immersing the end of the tubing in water in a beaker). to prevent the aluminium chloride from condensing in it. If this should happen at any particular point. The reaction is ended as soon as the aluminium. — this has been accomplished when the gas evolved is completely absorbed by water (a piece of rubber tubing is attached to the tube. In order that the cork may not burn. it is protected by an asbestos plate. but they should follow one another . are noticed.ALUMINIUM CHLORIDE 353 through the apparatus. since the acid foams easily. (3) The portion of the tube extending beyond the furnace must be as short as possible. disappears. white vapours of aluminium chloride. — the tube is heated in a combustion furnace throughout its entire length. due. which are gradually increased (Fig. (4) The aluminium must not be heated to melting. A<\ soon as the air is driven out of the apparatus. and treat with a solution of bleaching-powder. the latter is washed several times with water (decantation). a wet towel is placed on it and moistened from time to time. becomes deep dark brown. heat not quite to boiling. until the precipitate. or best. A small test-portion is then filtered hot. bright at first. it is selected of such a diameter that the glass tube can be fastened in it with a few turns of asbestos paper. but the greatest part of the aluminium chloride is condensed even if the hydrochloric acid rushes through the wash-bottles. Should the first experiment be unsuccessful. of water. wide (inner diameter). prepared by shaking 100 grammes of bleachingpowder with \\ litres of water and filtering. and thus a stopping up of the apparatus may be entirely prevented. with heat. Recently it has been shown that it is better to use for the receiver an iron tube 25 cm. The aluminium chloride condensing in the receiver is preserved in well-closed bottles. long. by filing it on the inside the end is given a somewhat conical shape . and then filtered with' suction. To one end of this is welded a narrower tube. 2 cm.c. and it is heated until a test gives no precipitate with the bleaching-powder solution. in consequence of a stoppage of the tube. If the iron tube should become too hot. The main quantity of the liquid is separated from the heavy precipitate by decantation. 13. A receiver of this kind is advantageous because the glass tube can be heated strongly to its extreme end. the precipi- . the method for correcting this will readily suggest itself. and the filtrate treated with the bleaching-powder solution and heated to boiling . The end not narrowed is closed by a cork bearing a glass tube as wide as possible leading to the hood. 50 grammes of lead acetate in 250 c. if a dark brown precipitate is formed. long and 4 cm. more of the bleachingpowder solution is added to the main quantity. in a desiccator. The evolution of a small quantity of a smoky vapour from the outlet-tube will always occur.354 SPECIAL PART uninterruptedly. LEAD PEROXIDE In a large porcelain dish dissolve. c. the chlorine evolved is passed into a solution of potassium iodide. a weighed portion is heated with hydrochloric acid. a cubic centimetre of the thiosulphate solution corresponds to ° ' ° 2 3 9 = . The determination. Value Determination. this is dissolved in enough cold water to make the volume of the solution just 250 c. first with sul- .5-1 gramme of the peroxide paste. CUPROUS CHLORIDE Heat a solution of 50 grammes of copper sulphate and 24 grammes of salt to 60-70°. When heat is applied to the flask. The contents of the retort are then poured into a beaker and treated with the thiosulphate solution from a burette until the yellow colour of the iodine just disappears. care is taken that the "potassium iodide solution is not drawn back into the flask. The precipitate is filtered with suction and washed. — In order to determine the value of the paste. The lead peroxide is not dried. Into this conduct a current of sulphur dioxide until the precipitate of cuprous chloride no longer increases. and which contains a solution of four grammes of potassium iodide in water. carried out as follows. and the liberated iodine is titrated with a — solution of sodium 10 thiosulphate (refer to a text-book on Volumetric Analysis). crystallised sodium thiosulphate. treat this (with cooling) with a mixture of equal volumes of concentrated hydrochloric acid and water.LEAD PEROXIDE 355 tate is washed repeatedly with water. the flask is immediately connected with a delivery tube. which liberates iodine from the potassium iodide. After the end of the heating. 14. and this is inserted in an inverted retort.2 grammes of pure. the neck of which has been expanded to a bulb. In a small flask weigh off 0. but is preserved in a closed vessel in the form of a thick paste. Since a molecule of the peroxide liberates two atoms of iodine. is sufficiently accurate for preparation work : On an analytical balance weigh off exactly 6.oi2 gramme pure lead peroxide. chlorine is generated. and the outlet tube with a nitrometer charged with a solution of caustic potash. From the volume of hydrogen obtained the percentage of zinc in the zinc dust may be calculated. of concentrated FIG. The individual operations of this analysis are conducted as described under " Determination of Nitrogen. The inlet tube is connected with a Kipp carbon dioxide generator.c. is allowed to flow in on the zinc dust. • Carbon • dioxide is passed into the apparatus until all the gas escaping from the outlet tube is absorbed by the potash. The moist preparation is then heated in a shallow porcelain dish or a large watch crystal on the water-bath until the odour of acetic acid cannot be detected.c.i gramme zinc dust (exact weighing) and add a few cubic centimetres of water. hydrochloric acid and 10 c.356 SPECIAL PART phurous acid and then with glacial acetic acid until it runs through colourless. 91). round flask o. DETERMINATION OF THE VALUE OP ZINC DUST From a weighing-tube pour into a ioo c.c. The flask is closed by a good three-hole cork. The stem of the funnel is previously filled with water by opening the cock. In the middle one is inserted a small dropping funnel. 15." . immersing the end in water and applying suction. the side holes carry the inlet and outlet tubes (Fig. The current of carbon dioxide is then lessened and from the dropping funnel a mixture of 10 c. water containing a few drops of platim'c' chloride. It is preserved in a wellclosed flask. the flask is finally heated. 91. 71. 188. 253. Azo dyes. Benzyl alcohol. 278. 335. Benzofcphenylester. Benzaldehyde. Autoclaves. 281. 143. 274. Brornethane." 31. 210. determination of. Ammonium eosin. 292. 204. 290. 357 . Chlorine. 274. Cleaning the hands. Chlorine. Benzophenone oxime. 337. Chioracetic acid. Acetic anhydride. 145. 137. Bitter almond green. 63. Bomb-furnace. Acetamide. Benzoyl chloride. Aldehyde. Benzenesulphon chloride. Briihl's apparatus. 253. "Bumping. Cinnamic acid. Benzil. 223. Boiling-point. Anthracene. 228.ene. 143. Acetic ester. 53. Collidine. Amidoa7. Benzenesulphinic acid. Bromben/. Benzene from aniline. 126. 244. Benzamide. 253. Bcnzal chloride. Acetonitrile. 61. Acetyl chloride. Benzophenone. 285. 45. 58. Aldehyde-ammonia. 304. 27. Active mandelic acid. Benzenesulphonic acid. Bromine. 292. 289. 231. Butlerow's Synthesis. Azines. 271. i6t. Beckmann's Reaction. 289. 127.INDEX Abbreviations. Alizarin. Benzoin. 75. 156. 276. 269. Aluminium chloride. 238.oben7. corrections of. 348. 274. 326. 121. determination of. Benzole acid. 36a Acetacetic ester. 229. 352. 199. Cleaning vessels. Benzidine. 32. 292. Benzene from phenylhydrazine. 269. 98. Azoxybenzene. Azobenzene. Bomb-tubes. determination of. 15. 75. Benzotrichloride. Carbon. 322. 131. 139. Bromine carrier. Butyric acid. Carbon monoxide. 343. Animal charcoal. Biichncr funnel. Anthraquinone. Aniline. 336. 70. 135. Benzyl chloride. Ammonia. Acetaldehyde. 258.ene. 271. Antipyrine. 333. 112. Benzenesulphon amide. 199. Amido<limethyl aniline. 246. determinations of. 51. Fractional crystallisation. 98. 330. 355. 244. 54. Diazo-compoundSj 210.358 Collidinedicarbonic ester. Iodobenzene. 212. Crystallisation. determination of. Methyl amine. . 217. Malonic ester. Hydrazobenzene. 113. Gattermann-Koch Reaction. 323. 234. Diazobenzeneperbromide. determination of. Drying. 48. Dihydrocollidinedicarbonic ester. 235. Ethylene bromide. 137* Ethyl benzene. 75. 320. 171. Fluor escem. Iodine. 211. Lead peroxide. Cuprous chloride. Methylene blue. Dimethylcyclohexenone. 176. Fractional distillation. 288. 171. 139. ' Isonitrile reaction. 261. 37. 250. Iodosobenzene. 227. 217. 264. Heating under pressure. Nitroaniline. 207. determination of. Ethy^alonic ester. Diphenyliodonium iodide. 217. 249. 323. 43. 303. 58. Iodine chloride. 337. 243. Hydroquinone. INDEX Fuchsine-paper. 229. Filter press. Hydrazones. Friedel-Crafts' Reaction. 177. 47. Crystal violet. 185. Halogens. Hydriodic acid. 354. Ethyl bromide. 231. 207. Glycol. Monochloracetic acid. pure. Mandelic acid. Iodoethane. 66. 152. Ethyl malonic acid. Disazo dyes. Mandelic nitrile. n . 199. Diphenylthiourea. Glycoldiacetate. 176. 166. 171. Michler's ketone. Diphenylmethane. 1. 45. 345. 345. 330. Diazobenzeneimide. Hydrogen. of vessels. Ethyl iodide. 279. 249. 18& Decolourising. Naphthalenesulphonic acid (0). 161. 29a. Ether. Drying. Guanidine. Inactive mandelic acid. 279. Distillation with steam. Filtration. Diazonium compounds. 210. 16. Drying agents. 231. Ethylene alcohol. 211. 301. Ethylene. Congo-paper. 161. Dibrombenzene. 75. Diazotisation. 162. Distillation. Melting-point. Hydrocinnamic acid. 70. 23. Fittig's Synthesis. 279. Hofmann Reaction. Monobrombenzene. 166. 338. 112. Diazoamidobenzene. 195. Eosin. Malachite green. Ethylidene bisacetacetic ester. Kolbe's Reaction. 316. 244. Hydrochloric acid. Naphthol(/3). Ethyl acetate. Knoevenagel's ring closing. 113. 343. Dinitrobenzene. Helianthine. Isodiazo compounds. 151. 141. Hydrobromic acid. 212. Extraction with ether. 235. hydrogen nitrogen. Tolyl nitrile. lodium. Potassium acetate. 45. Nitrophenol (o and p). 74. 63. Oxybenzaldchyde (p). 216. 348. Zinc dust determination. Quantitative determination of nitrogen. 351. . 258. 267. Tests for halogen. 227. 337. Phosphorus pentachloride. 348. 178. l'henyliodide. idvents. 63. 223. 127. Tests for carbon. Tarty matter. Terephthalic acid.' 44. Quantitative determination of carbon and hydrogen. 40. Osazones. 196. Vacuum distillation. 309. Sodium knife. 208. 217. 326. Sodium eosin. Phenyl mercaptan. Pipette. Thiocarbanilide. 85. 222. salicylic acid. Reduction of an azo dye. Phenylhydrazine. 335. Sulphurous acid. 356. 313. Pukall cells. determination of. Zinc dust distillation. bro mine. Jalicylic aldehyde. Quantitative determination of sulphu 81. saponiiication of ethyl malonic ester. Trimethylpyridine. 194. 217. Opening bomb tubes. >ulphanilic acid. 214. 73. 54. Qualitative tests for carbon. Nitroso benzene. 37. Phenyl mustard oil. 42. Phenylhydroxylamine. Tests for nitrogen. iodium amalgam. Toluic acid. 290. 229. Salting out. Phenyldisulphide. 340. sealing of bomb-tubes. 72. Quantitative determination of halogens. 2. 351. Triphenylguanidine. 260. 261. Sublimation. separation of liquids. removal of. 171. 205. Quinone. 316. 340. Perkin's Reaction. 206. Thiophenol. Runge's Reaction. 350. 239. lodium acetate. anhydrous. capillary. Nitrous acid. Quinuline. Volhard Tubes. 221. 351.INDEX Nitrobenzene. >team distillation. . 41. rhenyliodite. 285. Tolyl aldehyde. 85. Potassium-iodide-starch-paper. determination of. 352. 162. 58. sandmeyer's Reaction. Xylenol (s). 331. 81. 312. Tests for hydrogen. 307. 75. 69. chlorine. 344. Nitrogen. Sulphur. 303. Testing thermometers. 253. tests of. 72. •' mlphobenzide. Pyro-reaction. 359 iafety wash-bottle. Superheated steam. 206. Thenol from aniline. 25. 61. 69. 350. sulphur. khotten-Baumann Reaction. 217. iodine. 14. 185. 196. 72. Phenylibdide chloride. Tests for sulphur. Thermometer. Phosphorus trichloride. 98. Quinr/arin. Pressure flasks. 72. Phosphorus oxychloride. ABBREVIATIONS A. ch. J. Bl. Z. = Journal fur praktische Chemie. B. J. = Annales de chimie et de physique. = Journal der russischen chemischen Gesellschaft. = Zeitschrift fur Chemie. = Jahresbericht iiber die Fortschritte der Chemie. = Liebig's Annalen der Chemie. = Bulletin de la societe chimique de Paris. = Chemiker Zeitung. R. Ch-Z. A. pr. 360 . = Berliner Berichte. = PoggendorfP s Annalen. P.