CHEMISTRY 31.1 ORGANIC CHEMISTRY LABORATORY EXERCISE 10: Aldehydes and Ketones Submitted by: Abegail Mae S. Ramos II-BS Biology Laboratory Partners: Gabriel Paulo G. Eleria Marigold P. Araneta II-BS Biology However. giving a negative result. Howver. yielding yellow precipitate to methyl ethyl ketone and 2-butanol as well because it will also oxidize to methyl ketone. This happened because this test is extremely sensitive and may give false positives. Errors occurred in the experiment might be because of two factors. benzaldehyde and formalin turned its color to magenta. these compounds can be further analyzed as an individual entity and different from each other. an aldehyde and methyl ethyl ketone yielded yellow precipitate as an indication of positive test. For specific test of methyl ketones. . iodoform test was conducted. (1) not enough time for the reaction to occur and (2) quality of chemicals obtained. yielding brick red precipitate would distinguish aliphatic (formalin/formaldehyde) from aromatic. Aldehydes can be classified further into aromatic and aliphatic. Positive test in Benedict s test. though methyl ethyl ketone was supposed to be colorless.ABSTRACT 2. it also turned into magenta. As for specific positive test for aldehdyes through Schiff s reagent. Test compounds such as benzaldehyde.4-DNPH is a positive test for both aldehydes and ketones. H . (O'Leary.g. -C=O. Two of the simplest are propanone. Many aldehydes have pleasant odours. They are simple in the sense that they don't have other reactive groups like -OH or -Cl attached directly to the carbon atom in the carbonyl group . Wilson. 2000) A ketone is a compound containing a carbonyl group with two hydrocarbon groups attached to it.CHO).4-dinitrophenylhydrazine is often abbreviated to 2. marketed under the name methyl ethyl ketone or MEK. 2003) Any of a class of organic compounds. Aromatic aldehydes (e. are also known which undergo a number of chemical reaction which do nor occur for aliphatic aldehydes and which are unique to aromatic aldehydes. from which process came the name aldehyde.CHO. 2. and the solvent that the 2. A solution of 2. The aliphatic aldehydes are named by replacing "-e" at the end of the alkane from which they are derived with "-al".4-dinitrophenylhydrazine is dissolved in. (Shipman. Introducing Aldehydes and Ketones. (Aldehyde) The aliphatic aldehydes are a homologous series of organic compounds of carbon. a single bond with a hydrogen atom.a carbon-oxygen double bond. and 2-butanone. C6H5. in carboxylic acids containing -COOH. marketed under the name acetone. The general formula is CnH2n+2.INTRODUCTION Aldehydes and ketones are simple compounds which contain a carbonyl group .as you might find. they are derived from alcohols by dehydrogenation (removal of hydrogen). benzaldehyde. in which a carbon atom shares a double bond with an oxygen atom.4-DNPH.4-DNP or 2.4-dinitrophenylhydrazine in a mixture of methanol and sulphuric acid is known as Brady's reagent. for example. The double bond between carbon and oxygen is characteristic of all aldehydes and is known as the carbonyl group. (Clark. & Todd) . is contained within the molecule. Details vary slightly depending on the nature of the aldehyde or ketone. and in principle. where the aldehyde functional group. and a single bond with another atom or group of atoms (designated R in general chemical formulas and structure diagrams). hydrogen and oxygen. Formal names for ketones include the prefix from the alkyl group and the suffix one. ) + + - Table 2. METHODS Methods were taken by following the procedures instructed from Chemistry 31. Schiff s Test Test compounds Formalin Methyl Ethyl Ketone Benzaldehyde Color Magenta Pink Pink (daker than Methyl Ethyl Ketone) Table 4.4dinitrophenylhyrdazine reagent. Formation of precipitate from test compounds added with 95% ethanol and 2.OBJECTIVES The objective of the experiment was to be able to perform different test to aldehydes and ketones test compounds in order to observe and determine its positive and negative reactions. Iodoform Test . Test compounds Methyl Ethyl Ketone Benzaldehyde 1-Butanol Precipitate formed (in 15mins.1 Organic Chemistry on pages 73-75 with a slight modification of using Methyl Ethyl Ketone instead of acetone as a test compound. PRESENTATION OF RESULTS Table 1. Benedict s Test Test compounds Methyl Ethyl Ketone Benzaldehyde 1-Butanol Color after heating green Blue green No color change Color after adding/before heating bluish bluish bluish Table 3. 4-DNPH For the two compounds. The R and R in the reaction stands or any combination of hydrogen and hydrocarbon group. (Clark.4-DNPH adds the benaldehyde in its attached H to form water. the reaction is shown below: Figure 1. The mechanism is nucleophilic addition-elimination reaction because first the 2. the boxed portion the R and R groups has at least one attached hydrogen. For benzaldehyde. For Methyl ethyl ketone. the formed water is then eliminated and the product is an imine. the structure is shown below: . The positive reaction of test compounds with are summarized and generalized below. 2004). In this case.Test compounds Methyl Ethyl Ketone Ethyl alcohol 2-Butanol Color of precipitate formed yellow yellow DISCUSSION The 2. This means that benzaldehyde is an aldehyde. it is shown in the reaction. Reaction of benzaldehyde and 2. that small molecule is water.4-DNPH test is a positive test for aldehyde and ketone compounds. A condensation reaction is one in which two molecules join together with the loss of a small molecule in the process. The reaction is known as a condensation reaction. Later. The contributing factor of the errors might be the quality of the chemicals given because of changes in color that occurred to some test compounds. the reaction is condensation reaction and the mechanism is nucleophilic addition-elimination with formation of water and imine products. yielding brick red precipitate. From the table 2 above. 2004) Benedict s solution is a specific positive test for presence of aliphatic aldehyde that would yield brick red color. The same with benaldehyde s. as well as the time it took for the reaction to occur might be not enough on what was done in the experiment. Methyl Ethyl Ketone As shown in the structure. it should have no precipitate and would eventually retain its blue color of the solution. . The reaction is shown below. For Methyl Ethyl Ketone. Schiff s test is another positive test for aldehydes that would yield colorless to magenta color. Both benzaldehyde and Methyl Ethyl Ketone yielded with a yellow precipitate because of the presence of carbon-oxygen double bond (Clark. also known as methanal (Harrison. the structure is a ketone. Benedict s positive reaction Since benzaldehyde is an aromatic aldehyde. The reaction is shown below. Therefore. it has an attached hydrocarbon group (as boxed above). retaining a blue solution. since it is a ketone and definitely not an aldehyde. the results of the tests were random and would not give a wise interpretation of the reaction of aldehydes and ketones. in its reaction with 2.Figure 2. the results must have been that only formaldehyde. the expected result must have been no reaction. being an aliphatic aldehyde. since both has an attached hydrocarbon group. Nevertheless. 1998) would react.4-DNPH. Figure 3. The bisulfite reacts with the dye to produce a colorless solution. However. Methyl ethyl ketone should have resulted into colorless color since it is a ketone. (Experiment 13 Qualitative Tests for Carbonyls. all test compounds had positive result. Schiff s reagent is made by adding the intensely colored triphenylmethane dye called fuschsin to a solution of sodium bisulfate (NaHSO3). The positive reaction of Schiff s test In figure 4. In the experiment s result from table 3. The reason for this mishap might be because the experiment was not handled accordingly because this test is extremely sensitive and may give false positives. This colorless solution will then react with aldehydes but not ketones to produce a new triphenylmethane dye that also has a brilliant purple color. . (Experiment 13 Qualitative Tests for Carbonyls. Unknown Carbonyl).Figure 4. Unknown Carbonyl). yielding yellow precipitate. (Experiment 6 (Organic Chemistry II) Identification of Ketones and Aldehydes) CONCLUSION Aldehydes and Ketones can be distinguished through several tests. specific test for methyl ketones. (Shriner. forming yellow precipitate. . & Morrill. Methyl Ethyl Ketone from the experiment had positive result. 2001). Reaction of iodoform test The iodoform reaction is a classical test for methyl ketones. forming colorless to magenta color. A light yellow precipitate of iodoform forms immediately with the methyl ketone 2-pentanone. Q/A 1.4-DNPH.) Differentiate the following pairs by giving the reagent used in the exercise and the visible result: a. forming a yellow precipitate imine. Certain tests have positive specific reactions like in Schiff s reagent. and iodoform test. it is a positive test for both aldehydes and ketones. In reaction with 2. Even aldehydes can be further distinguished as aromatic or aliphatic through a positive test in Benedict s of brick red which is characterized as aliphatic aldehyde. it will only react with aldehydes. Secondary alcohols 2-butanol (isobutanol) will also oxidize to methyl ketone and give a positive test with iodoform.The general reaction for Iodoform test is shown below. Figure . Curtin. Fuson. Phenylactaldehyde and benzyl alcohol Phenylactaldehyde is an aromatic aldehyde while benzyl alcohol is an alcohol that will undergo oxidation in Iodoform test. (blue) Schiff s reagent colorless Iodoform test d. Compounds 2-pentone 3-pentone Reaction with 2. Compounds 2-pentanone 2-pentanol Reaction with 2. (blue) No ppt.Reaction with 2. 2-pentone and 3-pentone 2-pentone is a methyl ketone while 3-pentone is a diethyl ketone. Cyclohexanone and cyclohexyl methyl ether Compounds Cyclohexanone cyclohexyl methyl ether Reaction with 2.4-DNPH Yellow ppt. N/A c.4-DNPH Phenylactaldehyde Yellow ppt. (blue) n/a Schiff s reagent colorless n/a Iodoform test Yellow ppt. Yellow ppt. 2-pentanone and 2-pentanol 2-pentanone is a methyl ketone while 2-pentanol is an alcohol that will undergo oxidation in Iodoform test.) In the reaction of 2. what is the purpose of these derivatives? The reaction of aldehydes and ketones with ammonia or 1º-amines forms imine derivatives. (blue) Schiff s reagent colorless colorless Iodoform test Yellow ppt.4-DNPH Yellow ppt. n/a Benedict s Test No ppt. . Benedict s Test No ppt. benzyl alcohol N/A Compounds Benedict s Test No rxn (blue) N/A Schiff s reagent magenta N/A Iodoform test No ppt. (Carbonyl Reactivity).4-DNPH Yellow ppt. Yellow ppt. This reaction plays an important role in the synthesis of 2º-amines.4-dinitrophenylhydrazine with either aldehydes or ketones you form imines which are derivatives of either aldehydes or ketones. 2. Benedict s Test No ppt. also known as Schiff bases. (compounds having a C=N function). Yellow ppt. Yellow ppt b. HTM .. from SWC2. Formaldehyde .ie/academic/chem/dolchem/html/dict/aldehyde. Retrieved August 23. from http://www.edu/pahlavan/2425L6. from Encyclopedia Britannica eb..chemguide.hccs.msu.chemguide.pdf Harrison.com/moremolecules. Retrieved August 23.html Clark.d.edu/faculty/reusch/VirtTxtJml/aldket1.edu: http://phoenix. Retrieved August 23.html Shipman. 2010.co.d.pdf Experiment 6 (Organic Chemistry II) Identification of Ketones and Aldehydes.msu.chemistry. Retrieved August 23. Ketones. (2004).).d. 2010. J.d. 2010. 2010. R. from Chemistry Come Alive: http://jchemed. Aldehydes Aliphatic. (n. & Todd. & Morrill.htm Clark.asp?ID=101&othername=Methanal O'Leary. Retrieved August 23. from Phoenix.com: http://www.html Shriner.). Fuson.uk/organicprops/carbonyls/background. D.d.edu/hbase/organic/ketone. 2010. Addition-Elimination Reactions of Aldehydes AND Ketones.phy-astr.edu: http://www2. D. Retrieved August 23. 2010. Retrieved August 23. from Chemguide: http://www.ucc. 2010. July).com: http://www. (n. from chemistry. from Chemguide. Retrieved August 23.britannica. (2003). L.liu. (1998.edu/~nmatsuna/che122/exp13. C. Curtin.).co. R. from Hyperphysics***Chemistry: http://hyperphysics. (2001). Iodoform Test for Methyl Ketones. (n..).hccs.html Experiment 13 Qualitative Tests for Carbonyls. Retrieved August 23. Wilson. 2010.edu: http://swc2. Unknown Carbonyl.wisc.References Aldehyde. 2010. (n. Retrieved August 23.chem. (n.com: http://www. T.uk/organicprops/carbonyls/addelim.). (2000). Introducing Aldehydes and Ketones. Y. from Methanal @ 3Dchem.liu.edu/JCESoft/CCA/CCA5/MAIN/1ORGANIC/ORG12/TRAM12/C/0382204/MOV IE. C. Methanal .com/EBchecked/topic/13527/aldehyde Carbonyl Reactivity.gsu.3dchem. 2010. J. K.