NMR - Multiple Choice Questions

http://wps.pearsoned.co.uk/ema_uk_he_housecroft_chemistry_4/130/33535/8584987.cw/index.htmlhttp://wps .pearsoned.co.uk/ema_uk_he_housecroft_chemistry_4/130/33535/8584987.cw/index.html Multiple choice questions Try the following multiple choice questions to test your knowledge of this chapter. For each question there is one correct answer. The periodic table, physical constants and relative atomic masses needed for these problems are given on the inside covers of Chemistry, fourth edition by C.E. Housecroft and E.C. Constable. Once you have answered the questions, click on 'Submit Answers for Grading' to get your results. If your lecturer has requested that you send your results, please complete the routing information found at the bottom of your graded page and then click on the 'E-Mail Results' button. Please do not forward your results unless your lecturer has specifically requested that you do so. This activity contains 18 questions. For a nucleus with nuclear spin quantum number I = ½, what are the values of mI? +½, 0 +½, +1 0, +1 +½, –½ Which list below gives only spin active nuclei? 1 H, 13C, 19F H, 2H, 12C H, 12C, 19F H, 12C, 19F 1 2 1 Which carbon environment and 13C chemical shift range are correctly matched in the pairs below? aliphatic group RCH2X; δ +100 to +150 ppm alkene R2C=CR2; δ +50 to +80 ppm nitrile C≡N; δ +50 to +100 ppm ketone R2C=O; δ +190 to +230 ppm What do you expect to observe in the 1H NMR spectrum of chloroethane CH3CH2Cl? A doublet and a triplet. A doublet and a quartet. A triplet and a quartet. Two doublets. What signals do you expect to see in the 1H NMR spectrum of 1,1-dichloroethane CH3CHCl2? A singlet and a doublet. A doublet and a quartet. A doublet and a triplet. A singlet and a quartet. How many signals do you expect to see in the 1H NMR spectra of 2-bromopropane (CH3)2CHBr and 1- bromopropane CH3CH2CH2Br? 1-Bromopropane: 3; 2-bromopropane: 2. 1-Bromopropane: 2; 2-bromopropane: 2. 1-Bromopropane: 3; 2-bromopropane: 3. 1-Bromopropane: 2; 2-bromopropane: 3. The 13C NMR spectrum of a compound A contains two signals and in the 1H NMR spectrum there is a singlet. Which compound is consistent with these data? Ethanol. Acetone. Dichloromethane. Bromoethane. The 1H NMR spectrum of a compound B shows a doublet and a septet. Which of the following statements is true? The spectroscopic data are consistent with B containing a propyl (CH3CH2CH2) group. The spectroscopic data are consistent with B being (CH3)2CHCl. The spectroscopic data are consistent with B containing a CH3CH2 group. The spectroscopic data are consistent with B being (CH3)2CCl2. Compound D is not a carboxylic acid.A 1H NMR spectrum of compound C contains a singlet. Compound D is likely to contain aliphatic C atoms. a triplet and a quartet. which conclusion is incorrect? Compound D does not contain a ketone functional group. Which of the following compounds might C be? CH3CHClCHClCH3 CH3CCl2CH2CH3 CH3CH2CH2CHCl2 CH3CH2CHClCHCl2 The 13C NMR spectrum of a compound D shows three signals. Based on these data. all in the region δ +10 to +60 ppm. Which of the following compounds contains one or more protons that could undergo exchange with protons in water? CH3OH CH3Br (CH3)2O (CH3)3N . Compound D contains three C atoms. In the IR spectrum of a compound X. What are the multiplicities and assignments of these signals? A quartet assigned to the CH3 group and a doublet assigned to the CH group. The 1H NMR spectrum contains two signals: a quartet and a triplet with relative integrals of 2 : 3. The 1H NMR spectrum (recorded in CDCl3).A 1H NMR spectrum of CH3CHBr2 shows two signals. 1. Two singlets. A doublet assigned to the CH3 group and a quartet assigned to the CH group.08 ppm) and a sextet (δ 1.70 ppm) are observed. there is a strong absorption at 1718 cm–1 in addition to bands at 2978 and 2940 cm–1 and bands below 1500 cm–1. the IR spectrum of A contains a sharp band at 2250 cm–1.21 % H. Among other absorptions.52 % C and 10. one assigned to each of the CH3 and CH groups.34. which is X most likely to be? CH3CH2OCH2CH3 CH3CH2OH CH3CH2CO2H CH3CH2COCH2CH3 A compound A analyses as containing 69. Compound A is: CH3CH2CH2CHO CH3CH2CH2NH2 CH3CH2CH2CN (CH3)2CHCN . two triplets (δ 2. A triplet assigned to the CH3 group and a singlet assigned to the CH group. Of the following compounds. Which of the following compounds is Z most likely to be? CH3OCH2CH2OCH3 CH3CH2OCH2OCH2CH3 CH3OCH2OCH3 CH3CH2OCH2CH3 Vicinal coupling is: coupling between 1H nuclei attached to the same C atom. An AB pattern is observed. An AX pattern is observed.0 ppm. coupling between 1H nuclei in an alkane. . coupling between 1H nuclei in an alkene. coupling between 1H nuclei attached to adjacent C atoms. Which statement corresponds to the case where the chemical shift difference between two coupling protons is less than 5-times the coupling constant? A first-order spectrum is expected.9 and 59. while in the 1H NMR spectrum there are two singlets at δ 3.The 13C{1H} NMR spectrum of a CDCl3 solution of an ether Z exhibits signals at δ 71.55 and 3.39 ppm (relative integrals 3 : 2). For this doublet. δ +190 to +230 ppm 4.05 ppm when measured on a 100 MHz spectrometer. Which list below gives only spin active nuclei? 1 Your Answer: H. What signals do you expect to see in the 1H NMR spectrum of 1.0 Hz on a 500 MHz NMR spectrometer.1-dichloroethane CH3CHCl2? Your Answer: A doublet and a quartet. what are the values of mI? Your Answer: +½. 6. For this doublet. Which of the following statements is incorrect? The difference Δδ for the two components of this doublet depends on the field strength of the spectrometer. . For a nucleus with nuclear spin quantum number I = ½. the coupling constant is 5. 19 F 3. δ +100 to +150 ppm Correct Answer: ketone R2C=O. How many signals do you expect to see in the 1H NMR spectra of 2-bromopropane (CH3)2CHBr and 1bromopropane CH3CH2CH2Br? Your Answer: 1-Bromopropane: 2. 13 C. The difference Δδ for the two components of this doublet is 0. 2-bromopropane: 2.0 Hz when the spectrum of X is recorded on a 250 MHz NMR spectrometer. –½ 2. 1. Correct Answer: A triplet and a quartet. What do you expect to observe in the 1H NMR spectrum of chloroethane CH3CH2Cl? Your Answer: A doublet and a triplet. A 1H-1H coupling constant for a doublet in a compound X is measured as 5. Which carbon environment and 13 C chemical shift range are correctly matched in the pairs below? Your Answer: aliphatic group RCH2X. 5. the coupling constant measured in Hz depends on the field strength of the spectrometer.An undistorted binomial splitting pattern is expected. The 13C NMR spectrum of a compound A contains two signals and in the 1H NMR spectrum there is a singlet. the IR spectrum of A contains a sharp band at 2250 cm–1. Which compound is consistent with these data? Your Answer: Acetone. 7. which conclusion is incorrect? Your Answer: Compound D is likely to contain aliphatic C atoms. What are the multiplicities and assignments of these signals? Your Answer: A triplet assigned to the CH3 group and a singlet assigned to the CH group. there is a strong absorption at 1718 cm–1 in addition to bands at 2978 and 2940 cm–1 and bands below 1500 cm–1. A 1H NMR spectrum of compound C contains a singlet.70 ppm) are observed. 1. Correct Answer: A doublet assigned to the CH3 group and a quartet assigned to the CH group. Of the following compounds. Which of the following compounds contains one or more protons that could undergo exchange with protons in water? Your Answer: (CH3)2O Correct Answer: CH3OH 12.9 and 59. while in the 1H NMR spectrum there are two singlets atδ 3. 9. Among other absorptions. 8.0 ppm. The 1H NMR spectrum of a compound B shows a doublet and a septet. The 1H NMR spectrum (recorded in CDCl3). Which of the following statements is true? Your Answer: The spectroscopic data are consistent with B being (CH3)2CHCl.21 % H.52 % C and 10. The 13C NMR spectrum of a compound D shows three signals. two triplets (δ 2. a triplet and a quartet. 13.Correct Answer: 1-Bromopropane: 3. Which of the following compounds might C be? Your Answer: CH3CH2CH2CHCl2 Correct Answer: CH3CCl2CH2CH3 10. A 1H NMR spectrum of CH3CHBr2 shows two signals.34. 11. Based on these data.39 ppm (relative integrals 3 : 2). The 13C{1H} NMR spectrum of a CDCl3 solution of an ether Z exhibits signals at δ 71.55 and 3. The 1H NMR spectrum contains two signals: a quartet and a triplet with relative integrals of 2 : 3. Compound A is: Your Answer: CH3CH2CH2CHO Correct Answer: CH3CH2CH2CN 15. Which of the following compounds is Z most likely to be? Your Answer: CH3CH2OCH2OCH2CH3 Correct Answer: CH3OCH2CH2OCH3 . 2-bromopropane: 2. Correct Answer: Compound D contains three C atoms. In the IR spectrum of a compound X. all in the region δ +10 to +60 ppm. which is X most likely to be? Your Answer: CH3CH2OH Correct Answer: CH3CH2COCH2CH3 14.08 ppm) and a sextet (δ 1. A compound A analyses as containing 69. Which of the following statements isincorrect? Your Answer: For this doublet. 17. Correct Answer: For this doublet. Which statement corresponds to the case where the chemical shift difference between two coupling protons is less than 5-times the coupling constant? Your Answer: An AX pattern is observed. Correct Answer: An AB pattern is observed. 18.16. Vicinal coupling is: 1 Your Answer: coupling between H nuclei attached to adjacent C atoms. A 1H-1H coupling constant for a doublet in a compound X is measured as 5. the coupling constant measured in Hz depends on the field strength of the spectrometer. .0 Hz on a 500 MHz NMR spectrometer.0 Hz when the spectrum of X is recorded on a 250 MHz NMR spectrometer. the coupling constant is 5. The CMR spectrum of an unknown compound shows 4 absorptions and the PMR spectrum shows 4 absorptions. Which of the following compounds is the unknown compound? 4.edu/people/richardbanks/organic/mc/vol3/mcquestions317c. How many absorptions will the following compound have in its carbon NMR spectrum? (a) (b) (c) (d) 3 4 5 6 3. Which of the following compounds is the unknown compound? .boisestate. The CMR spectrum of an unknown compound shows 6 absorptions and the PMR spectrum shows 5 absorptions.http://chemistry. Which of the following nuclei will have a magnetic moment? 2.htm Organic Chemistry Practice Multiple Choice Question Set 3 1. Which of the following alkyl groups would show the multiplet pattern depicted in the diagram? . Which of the following compounds best fits the PMR spectrum shown below.5. What is the multiplicity expected in the hydrogen NMR spectrum for the hydrogen atoms marked by a "star" in the following compound? (a) (b) (c) (d) singlet triplet quartet heptet 6. 7. The table shows the chemical shift for groups attached to a bromine atom or a cyano group measured to the center of the multiplet. 2c This answer is not correct. 2a -This answer is not correct.Copyright © August 2000 by Richard C. 1b -This answer is not correct. Nuclei that have an odd atomic number. 3b You are correct! 3c This answer is not correct. odd atomic mass or both will have magnetic moments. Every carbon atom has a hydrogen atom bonded to it so the number of hydrogen absorptions must equal the number of carbon absorptions. There are 4 absorptions for both spectra for this compound..their neighboring atoms. 3d This answer is not correct. 2d .. Think about the geometry of the compound and the neighboring atoms.. This nucleus has an even atomic number and an even atomic mass. Double bonds are not free to rotate and one of the methyl groups is on the side of the double bond with the ethyl group whereas the other methyl group is on the side of the double bond with the hydrogen atom. odd atomic mass or both will have magnetic moments. See if you can find a better answer with this thought in mind.all rights reserved.their neighboring atoms. odd atomic mass or both will have magnetic moments.and try another selection. There are 5 absorptions for both spectra for this compound. 2b -This answer is not correct.. 1d This answer is not correct. Every carbon atom has a hydrogen atom bonded to it so the number of hydrogen absorptions must equal the number of carbon absorptions. Think about the unique positions of the groups.. Remember that each unique position of an atom will have a unique absorption.. Perhaps you thought that all of the methyl groups were equivalent in the structure. Think about the unique positions of the groups. They are all the same and should be counted as 1 absorption. This nucleus has an even atomic number and an even atomic mass. Remember that each unique position of an atom will have a unique absorption. .You are correct! Nuclei that have an odd atomic number.. Nuclei that have an odd atomic number. Nuclei that have an odd atomic number. 1a . odd atomic mass or both will have magnetic moments. This nucleus has an even atomic number and an even atomic mass.. Perhaps you thought that only 2 of the 3 methyl groups on the left side of the molecule were equivalent. 1c This answer is not correct. Banks...and try another selection. The mistake that you made is thinking that the geminal methyl groups were equivalent. Think about the geometry of the compound and the neighboring atoms.You are correct! 3a This answer is not correct. . 4d This answer is not correct.4a You are correct! There should be equal numbers of absorptions in both spectra and there are 4 unique positions in the molecule.. 4c This answer is not correct... 5a This answer is not correct.. 4b This answer is not correct. Note that the molecule is symmetrical with respect to the red line. Note that the molecule is symmetrical with respect to the red line. How many hydrogen atoms are on adjacent carbon atoms? ... The hydrogen atoms on adjacent carbon atoms can "couple" with these hydrogen atoms and split the absorption into multiple lines (multiplet).the number of lines = n+1 where "n" = the number of hydrogen atoms on adjacent carbon atoms. Note that the molecule is symmetrical with respect to the red line.. The formula for calculating the lines for a multiplet based on adjacent hydrogen atoms having a spin quantum number of ½ is. The formula for calculating the lines for a multiplet based on adjacent hydrogen atoms having a spin quantum number of ½ is. Note that the molecule is symmetrical with respect to the red line. There should be 4 hydrogen absorptions and 5 carbon absorptions for this molecule... There should be equal numbers of absorptions in both spectra for this compound and there are only 3 unique positions in the molecule. The hydrogen atoms on adjacent carbon atoms can "couple" with these hydrogen atoms and split the absorption into multiple lines (multiplet).. There should be equal numbers of absorptions in both spectra for this compound and there are 5 unique positions in the molecule. How many hydrogen atoms are on adjacent carbon atoms? 5bThis answer is not correct.the number of lines = n+1 where "n" = the number of hydrogen atoms on adjacent carbon atoms.. Remember that there is no hydrogen atom on the carbon atom with the geminal methyl groups. cw/index.. 7c This answer is not correct. 6c This answer is not correct. See if another answer better fits the data. The isopropyl group should also show an upfield doublet and a downfield heptet and the multiplets in the spectrum are a triplet and a quartet.html . 7a You are correct! The isobutyl group will show a large upfield doublet for the 2 methyl groups. 7d This answer is not correct. With this in mind.9 ppm but the downfield multiplet in the spectrum is at 3. The 1-propyl group will show 3 absorptions but the downfield absorption will be a triplet as will the upfield absorption. The secondary butyl group will show 4 unique absorptions instead of 3 and the multiplicities of the groups will be completely different than the pattern shown.4 ppm. The formula then give 3+1=4.pearsoned. These hydrogen atoms are too far distant to show coupling. a small downfield doublet for the methylene group and a "triplet of heptets" for the methine group. The chemical shift for a methine group attached to a cyano group should be 2. Perhaps you thought that the methyl group attached to the carbonyl group coupled with the methylene hydrogen atoms. The chemical shift for a methylene group attached to a cyano group is 2. 6d This answer is not correct. Only hydrogen atoms on adjacent carbon atoms can "couple" with these hydrogen atoms. Think about the number of absorptions and also the number of hydrogen atoms on adjacent carbon atoms and try again..9 ppm whereas the downfield multiplet in the spectrum is at 3. ============================================================================ http://wps. The central methylene group will be a triplet of quartets.4 ppm.co. 7bThis answer is not correct. This group will show a very large upfield singlet for the 3 methyl groups. select another answer. Think about both the chemical shift and the group pattern and try again. a small downfield triplet for the terminal methylene group and another triplet for the other methylene group.5c You are correct! The number of hydrogen atoms on the adjacent carbon atom is 3.uk/ema_uk_he_housecroft_chemistry_4/130/33534/8584911.it will look a lot like a hextet. 5d This answer is not correct. physical constants and relative atomic masses needed for these problems are given on the inside covers of Chemistry.C. The periodic table.E. Colorimeter. Radiowave. Solution concentration. Housecroft and E. What is the corresponding wavelength? 560 nm 180 000 cm–1 5. Coulometer. The frequency of a transition is 5. If your lecturer has requested that you send your results. This activity contains 18 questions. A solution of X of concentration 0.6 × 10–6 m 5. In what part of the electromagnetic spectrum does this come? Infrared.Introduction to spectroscopy Multiple choice questions Try the following multiple choice questions to test your knowledge of this chapter. Microwave. Distance that the light has travelled through the sample. Please do not forward your results unless your lecturer has specifically requested that you do so.6 × 10–8 m According to the Beer-Lambert Law.5.4 × 1015 Hz. click on 'Submit Answers for Grading' to get your results. For each question there is one correct answer. please complete the routing information found at the bottom of your graded page and then click on the 'E-Mail Results' button. Calorimeter. What is the name of an instrument used to measure the absorbance of a coloured compound in solution? Colourmeter. Once you have answered the questions. The wavenumber of a transition is 2000 cm–1. Colour of the solution. What concentration is a .010 mol dm–3 gives an absorbance of 0. fourth edition by C. Ultraviolet-visible. on which of the following does absorbance not depend? Extinction coefficient of the sample. Constable. 0. In what part of the electromagnetic spectrum does this lie? Radiowave.0 × 10–4 mol dm–3 0. what can you conclude? The dichromate ion absorbs in the ultraviolet region.25? Assume that the same optical cell is used for both readings. The dichromate ion absorbs outside the visible region. . Ultraviolet-visible. A solution of a dye absorbs light of wavelength 480 nm.5 × 10–4 mol dm–3 cm–1 The dichromate ion absorbs light of wavelength close to 500 nm.0 × 10–8 mol dm–3 9. A sample of the dye of unknown concentration is placed in an optical cell of path length 1 cm and the absorbance reading is 0.solution of X which gives an absorbance reading of 0. Solutions of the dichromate ion are colourless. What is the concentration of the solution? 2. The dichromate ion absorbs within the visible region.18. and for this absorption. What is the value of the molar extinction (absorption) coefficient of Z? 15 dm3 mol–1 cm–1 1500 dm3 mol–1 cm–1 150 dm3 mol–1 cm–1 1.0050 mol dm–3 0. Based on this information. Infrared. Microwave.010 mol dm–3 0.020 mol dm–3 Compound Z absorbs light of wavelength 320 nm.0 × 10–3 mol dm–3 solution of a compound Z gives an absorbance reading of 0.15 when placed in a solution cell of path length 1 cm.026 mol dm–3 The wavelength of an absorption is 495 nm.050 mol dm–3 0.7 × 10–6 mol dm–3 3. the extinction coefficient is 18600 dm3 mol–1 cm–1. A 1. Infrared radiation has a lower wavenumber than visible light. . A plot of absorbance against concentration is: linear with a negative gradient. Wavenumber is directly proportional to energy. an exponential curve. non-linear. Microwave radiation possesses more energy than infrared radiation.1 × 10–44 J 2. A solution of compound Z absorbs light of wavelength 256 nm.0 × 10–23 kJ Which of the following statements is correct? Infrared radiation has a shorter wavelength than visible light.The frequency of a transition is 3. Wavenumber is directly proportional to wavelength. Ultraviolet radiation has a longer wavelength than infrared radiation. log ε = 3.1 × 1010 Hz.21? 5. linear with a positive gradient.064 mol dm–3 Which statement is correct? Wavelength is directly proportional to energy.0 × 10–4mol dm–3 1. Aqueous KMnO4 solutions are purple. Wavelength is directly proportional to frequency.3.1 × 10–4 mol dm–3 2. What is the energy of this transition? 2.4 × 10–3 mol dm–3 0.0 × 10–23 J 2.1 × 10–44 kJ 2. and for this absorption. What is the concentration of a solution of Z (in an optical cell of path length 1 cm) that gives the absorbance reading is 0. What is the corresponding absorbance.35 mol dm–3 Results for: "Multiple choice questions" 1.5 A copper(II) sulfate solution of unknown concentration is placed in a colorimeter and an absorbance reading of 0.295 0.00 cm? 0. a shift to lower wavelength. 2. What is the corresponding wavelength? . Using the same solution cell.0340 0. if the path length of the solution cell used for the measurement is 1.100 mol dm–3 aqueous solution of a nickel(II) salt shows three absorbances.041 mol dm–3 8.340 29. An absorption in an electronic spectrum is recorded at 17 000 cm–1. The wavenumber of a transition is 2000 cm–1.A shift to lower wavenumber for an absorption in a spectrum corresponds to: a shift to higher energy.95 dm3 mol–1cm–1.46 is recorded. What is the concentration of the first solution? 0.34. a 0. The frequency of a transition is 5.074 mol dm–3 0.60 × 10–3 mol dm–3 0.055 Μ solution of copper(II) sulfate gives an absorbance reading of 0. a shift to lower frequency. What does this correspond to in nm? 59 nm 5900 nm 590 nm 59 000 nm A 0.4 × 1015 Hz. one of which has a value of ε = 2. In what part of the electromagnetic spectrum does this come? Your Answer: Infrared. a loss of intensity. 5. Correct Answer: Colour of the solution. What is the energy of this transition? –23 J Your Answer: 2.–1 Your Answer: 180 000 cm –8 Correct Answer: 5. The frequency of a transition is 3. what can you conclude? Your Answer: The dichromate ion absorbs in the ultraviolet region. the extinction coefficient is 18600 dm3 mol–1 cm–1. 4. A 1. The wavelength of an absorption is 495 nm. 5.6 × 10 m 3. What concentration is a solution of X which gives an absorbance reading of 0. A solution of compound Z absorbs light of wavelength 256 nm.0 × 10 11. and for this absorption. The dichromate ion absorbs light of wavelength close to 500 nm.1 × 1010 Hz.25? Assume that the same optical cell is used for both readings. Correct Answer: Ultraviolet-visible. 12. According to the Beer-Lambert Law. Based on this information. Compound Z absorbs light of wavelength 320 nm.0 × 10 mol dm –4 –3 Correct Answer: 1. A solution of X of concentration 0.0 × 10 –3 mol dm–3 solution of a compound Z gives an absorbance reading of 0. and for this absorption. log ε = 3.3.7 × 10 mol dm 9. 8. What is the name of an instrument used to measure the absorbance of a coloured compound in solution? Your Answer: Colorimeter. A solution of a dye absorbs light of wavelength 480 nm. What is the concentration of the solution? –6 –3 Your Answer: 9. Correct Answer: The dichromate ion absorbs within the visible region.15 when placed in a solution cell of path length 1 cm. What is the concentration of a solution of Z (in an optical cell of path length 1 cm) that gives the absorbance reading is 0.21? –4 –3 Your Answer: 5.18. –3 Your Answer: 0. What is the value of the molar extinction (absorption) coefficient of Z? 3 –1 –1 Your Answer: 1500 dm mol cm 3 –1 –1 Correct Answer: 150 dm mol cm 7. A sample of the dye of unknown concentration is placed in an optical cell of path length 1 cm and the absorbance reading is 0.1 × 10 mol dm . In what part of the electromagnetic spectrum does this lie? Your Answer: Microwave. 10. on which of the following does absorbance not depend? Your Answer: Extinction coefficient of the sample.010 mol dm–3 gives an absorbance of 0. Which of the following statements is correct? Your Answer: Infrared radiation has a lower wavenumber than visible light.0050 mol dm 6. The molecule is vibrating.34. The molecule is static in its ground state.00 cm? Your Answer: 0. If your lecturer has requested that you send your results. Which statement is correct about the vibrational ground state of an H2 molecule? The molecule is in its lowest vibrational level but is not vibrating.E. Once you have answered the questions. 16.95 dm3 mol–1 cm–1. a 0. A 0. 15. A shift to lower wavenumber for an absorption in a spectrum corresponds to: Your Answer: a loss of intensity.13.C. please complete the routing information found at the bottom of your graded page and then click on the 'E-Mail Results' button. A copper(II) sulfate solution of unknown concentration is placed in a colorimeter and an absorbance reading of 0. physical constants and relative atomic masses needed for these problems are given on the inside covers of Chemistry. Correct Answer: a shift to lower frequency. A plot of absorbance against concentration is: Your Answer: linear with a positive gradient. In its vibrational ground state.055 Μ solution of copper(II) sulfate gives an absorbance reading of 0. What is the corresponding absorbance. This activity contains 18 questions. For each question there is one correct answer. Using the same solution cell.074 mol dm ================================ Vibrational Rotational Spectroscopy Multiple choice questions Try the following multiple choice questions to test your knowledge of this chapter. What is the concentration of the first solution? –3 Your Answer: 0.46 is recorded. if the path length of the solution cell used for the measurement is 1. . Housecroft and E. Constable. fourth edition by C. Please do not forward your results unless your lecturer has specifically requested that you do so. click on 'Submit Answers for Grading' to get your results.295 18. Which statement is correct? Your Answer: (blank) 14. one of which has a value of ε = 2. An absorption in an electronic spectrum is recorded at 17 000 cm–1. What does this correspond to in nm? Your Answer: 590 nm 17. the molecule has no vibrational energy. Aqueous KMnO4 solutions are purple.100 mol dm–3 aqueous solution of a nickel(II) salt shows three absorbances. The periodic table. Which statement is incorrect about CO2? The IR spectrum of CO2 shows four absorptions.30 × 1026 kg 1.59 × 10–27 kg 1. H2S. In the IR spectrum of a ketone (R2C=O). Which statement is incorrect about H2O? H2O is non-linear. CO2 has two degenerate bending modes of vibration. Which pair is correct? CO2. Less energy is required to dissociate CS than CO. CO2 has two stretching modes of vibration. in what approximate region would you expect to find an absorption assigned to the C=O stretch? . 3. SO2. H2O undergoes symmetric and asymmetric stretching modes of vibration. CO2 is linear. Stretching the bond in CO requires less energy than stretching the bond in CS. 3. 3.75 × 10–27 kg 5. 4. Match the molecular formula to the number of degrees of vibrational freedom. H2O has four degrees of vibrational freedom. Which statement is incorrect? The wavenumber associated with the stretching of CO is higher than that of CS. CS2.Which value is the correct reduced mass of HF? 6. H2O has three IR active modes of vibration.72 × 1026 kg The force constants for CO and CS are 1902 and 849 N m–1 respectively. The trend in bond energies for CO and CS follows the trend in force constants. 2876 and 2120 cm –1as well as absorptions below 1500 cm–1. Stretching of the C(sp3)–H bonds gives rise to absorptions at lower wavenumbers than stretching of the C( sp2)–H bonds. 3311 cm–1 n-Propylbenzene contains C(sp2)–H and C(sp3)–H bonds. 3028. 2962. 2962 cm–1. 2945. The remaining part of the molecule contains CH2 groups and a terminal CH3 group. H–C(alkyne). H–C(alkyne). Absorptions at 2960. 2931 and 2873 cm–1 are assigned to the stretching of the C(sp3)–H bonds. 2120 cm–1 C≡C. 2120 cm–1. 2876 cm–1 C≡C. Each absorption can be assigned to the stretching mode of a particular bond in the propylbenzene molecule. H–C(alkyne). 2120 cm–1. 2833 and 1030 cm–1. 2931 and 2873 cm –1 as well as bands below 1600 cm–1. 3311 cm–1 C≡C. H–C(alkyne). The IR spectrum of hex-1-yne shows relatively strong absorptions at 3311.2000-2100 cm–1 1900-2000 cm–1 1400-1500 cm–1 1700-1750 cm–1 Which is the correct sequence of wavenumbers associated with the stretching of the following bonds? C–I > C–Cl < C=O < C≡N C–I < C–Cl < C=O < C≡N C–I > C–Cl > C=O > C≡N C–I > C–Cl > C=O < C≡N The IR spectrum of methanol (CH3OH) shows strong absorptions at 3340 (broad). The IR spectrum of propylbenzene contains strong or medium absorptions at 3085. Which statement is incorrect? Absorptions at 3085. . Which band is assigned to the O–H stretch? 1030 cm–1 2833 cm–1 2945 cm–1 3340 cm–1 Hex-1-yne is a hydrocarbon with a terminal H–C≡C– (alkyne) group. 2937. 3064 and 3028 cm–1 are assigned to the stretching of the C(sp2)–H bonds. Which bands are assigned to the C≡C and terminal H–C(alkyne) stretches? C≡C. 3311 cm–1. 3064. 2960. A bending mode.34 × 10–37 kg m2 1. The absorption at 3331 cm–1 becomes more intense. 3.008. A new band near to 2500 cm–1 is observed. 79Br = 78. and IB = IC IA = 0. Which is the correct assignment of this absorption? The stretching of one C–Br bond. and IB = IC IA = IB = IC .00 × 1046 kg m2 2. The symmetric stretching of the four C–Br bonds. Which of the following statements correctly describes what happens if the IR spectrum is re-recorded after D2O has been added to the alcohol? A new band near to 3800 cm–1 is observed. of 1H79Br if the bond distance is 142 pm? Atomic masses are: 1H = 1.22 × 10–7 kg m2 Which of the following statements is correct about the principal moments of inertia of an XY molecule that lies on the A axis? IA = IB.92. IB. The asymmetric stretching of the four C –Br bonds. and IC = 0 IA > IB. The absorption at 3331 cm–1 becomes very sharp. The force constant for the bond in NO is 1595 N m–1.The IR spectrum of CBr4 has a strong absorption at 667 cm–1.33 × 10–47 kg m2 3. Where will you observe an absorption in the IR spectrum of NO assigned to the stretching mode? 1903 cm–1 1193 cm–1 190 cm–1 2170 cm–1 The IR spectrum of liquid cyclohexanol contains a broad band at 3331 cm–1. What is the moment of inertia. Which statement is incorrect? Your Answer: Stretching the bond in CO requires less energy than stretching the bond in CS.59 × 10 3. Which statement is incorrect about CO2? Your Answer: The IR spectrum of CO2 shows four absorptions. Match the molecular formula to the number of degrees of vibrational freedom. Which statement is incorrect about H2O? Your Answer: H2O undergoes symmetric and asymmetric stretching modes of vibration. 6. Which pair is correct? Your Answer: H2S. Correct Answer: SO2. Correct Answer: H2O has four degrees of vibrational freedom. 3. Correct Answer: The molecule is vibrating. the molecule has no vibrational energy. The force constants for CO and CS are 1902 and 849 N m–1 respectively.For which of the following molecules could a pure rotational spectrum not be observed in the gas phase? N2 HCl CO NO Which of the following transitions between rotational energy levels is not allowed? J=1←J=3 J=0←J=1 J=1→ J=0 J=1←J=2 Results for: "Multiple choice questions" 1. 4.75 × 10 –27 kg Correct Answer: 1. 4. Which value is the correct reduced mass of HF? –27 kg Your Answer: 1. Which statement is correct about the vibrational ground state of an H2 molecule? Your Answer: In its vibrational ground state. . 5. 2. The IR spectrum of propylbenzene contains strong or medium absorptions at 3085. 2931 and 2873 cm –1 as well as bands below 1600 cm–1. 2876 and 2120 cm–1 as well as absorptions below 1500 cm–1. Which is the correct sequence of wavenumbers associated with the stretching of the following bonds? Your Answer: C–I > C–Cl > C=O > C≡N Correct Answer: C–I < C–Cl < C=O < C≡N 9. of 1H79Br if the bond distance is 142 pm? Atomic masses are: 1H = 1. The force constant for the bond in NO is 1595 N m–1. The remaining part of the molecule contains CH2 groups and a terminal CH3 group. The IR spectrum of hex-1-yne shows relatively strong absorptions at 3311. n-Propylbenzene contains C(sp2)–H and C(sp3)–H bonds. Which is the correct assignment of this absorption? Your Answer: The symmetric stretching of the four C–Br bonds. H–C(alkyne).7. 15. Which of the following statements is correct about the principal moments of inertia of an XY molecule that lies on . 3064. 78. 2960. in what approximate region would you expect to find an absorption assigned to the C=O stretch? –1 Your Answer: 2000-2100 cm –1 Correct Answer: 1700-1750 cm 8. 3311 cm 11. The IR spectrum of methanol (CH3OH) shows strong absorptions at 3340 (broad). 13. 2962. 2945. Hex-1-yne is a hydrocarbon with a terminal H –C≡C– (alkyne) group.92. 2120 cm –1 –1 Correct Answer: C≡C. IB. Which bands are assigned to the C≡C and terminal H–C(alkyne) stretches? –1 –1 Your Answer: C≡C. Which band is assigned to the O–H stretch? –1 Your Answer: 2833 cm –1 Correct Answer: 3340 cm 10. The IR spectrum of CBr4 has a strong absorption at 667 cm–1. 12. 3028. 3311 cm . H–C(alkyne). What is the moment of inertia. 2937. 46 2 Your Answer: 3. In the IR spectrum of a ketone (R2C=O). 2833 and 1030 cm–1. –1 Correct Answer: A new band near to 2500 cm is observed. Which of the following statements correctly describes what happens if the IR spectrum is re-recorded after D2O has been added to the alcohol? –1 Your Answer: The absorption at 3331 cm becomes very sharp. Which statement is incorrect? Your Answer: Each absorption can be assigned to the stretching mode of a particular bond in the propylbenzene molecule.008.33 × 10 79 Br = 16. The IR spectrum of liquid cyclohexanol contains a broad band at 3331 cm –1. Correct Answer: The asymmetric stretching of the four C –Br bonds. Where will you observe an absorption in the IR spectrum of NO assigned to the stretching mode? –1 Your Answer: 1193 cm –1 Correct Answer: 1903 cm 14.00 × 10 kg m –47 kg m2 Correct Answer: 3. 2120 cm . physical constants and relative atomic masses needed for these problems are given on the inside covers of Chemistry. Vacuum-UV.C. This activity contains 18 questions. A solution of 0. Infrared. and the absorption spectrum is recorded. . The periodic table. What are the correct units of εmax? mol dm–3 cm–1 cm mol dm–3 cm dm3 mol–1 dm3 mol–1 cm–1 In which region of the electromagnetic spectrum does an absorption at 177 nm come? Visible. If your lecturer has requested that you send your results. The absorptions have characteristic λmax and εmax values. For which of the following molecules could a pure rotational spectrum not be observed in the gas phase? Your Answer: CO Correct Answer: N2 18. Vacuum-UV. click on 'Submit Answers for Grading' to get your result s. please complete the routing information found at the bottom of your graded page and then click on the 'E-Mail Results' button. and IB = IC 17. Housecroft and E. Near -UV.001 mol dm–3 NiSO4 is placed in an optical cell of pathlength 1 cm. Visible. fourth edition by C. Once you have answered the questions. Which of the following transitions between rotational energy levels is not allowed? Your Answer: J = 1 ← J = 3 Electronic Spectroscopy Multiple choice questions Try the following multiple choice questions to test your knowledge of this chapter. In which region of the electromagnetic spectrum does an absorption at 600 nm come? Near -UV. For each question there is one correct answer. Please do not forward your results unless your lecturer has specifically requested that you do so. Constable.the A axis? Your Answer: IA = 0.E. A coloured compound. transition from a non-bonding MO to ζ* MO. The shifting of an absorption to shorter wavelength. How do values of λmax for the π*←π transitions vary among a series of conjugated polyenes? Values shift to longer wavelength as the number of C=C double bonds increases.Infrared. Values shift to shorter wavelength as the number of C=C double bonds increases. What is a chromophore? A group of atoms in a coloured compound. What does the notation σ*←n mean? Absorption. What is a red shift? The shifting of an absorption towards the blue end of the spectrum. transition from a quantum level n to ζ* MO. transition from a quantum level n to ζ* MO. The shifting of an absorption to higher energy. A group of atoms in a compound responsible for the absorption of electromagnetic radiation. Emission. The shifting of an absorption to lower energy. Values vary but in no particular pattern. Absorption. Which of the following is the principal chromophore in an azo-dye? N=N C=N N≡N C≡N . Emission. A group of atoms in a compound responsible for electromagnetic radiation. Values vary very little. transition from a non-bonding MO to ζ* MO. Blue. In both. What colour of light does lycopene absorb? Red. In both.Lycopene (λmax = 469 nm) is present in tomatoes.β-unsaturated ketone. the C atoms are all sp2 hybridized. Both have four π MOs. All but one of the following groups can donate a lone pair of electrons into the carbon π-system of a conjugated polyene. Allyl anion. Orange. Buta-1.3-diene? Both have four π-electrons. Green. In which of the following are the π-electrons not delocalized? Hepta-1. Which is the odd one out? OMe Me SMe NMe2 Which statement is incorrect about the allyl anion and buta-1. An α. Which of the following arrangements of carbon-carbon double bonds along the backbone of a polyene does not correspond to a conjugated system? –C=C–C=C–C=C– –C=C–C=C–C=C–C=C– –C=C–C–C=C– –C=C–C=C– . the π-bonding is delocalized.6-diene.3-diene. An aqueous solution of a dye has a strong absorption with λmax= 464 nm. orange. The electronic spectrum of solution A contained one absorption at λmax = 230 nm. The absorption of a photon is slower than the timescale of molecular vibrations. Solution A was of concentration 0. A compound X is characterized in its electronic spectrum by an absorption with λmax = 217 nm (εmax = 21 000 dm3 mol–1 cm–1). the value of εmax depends on concentration. Two solutions of the same compound were made up.66 × 10–2 mol dm–3. X is most likely to be: β-carotene. electronic spectroscopic data are not always reproducible.3-diene. Which of the following absorption maxima is not in the visible range of the electronic spectrum? λmax = 550 nm λmax = 250 nm λmax = 750 nm λmax = 480 nm Which of the following statements is consistent with an electronic absorption being broad? Hydrogen bonding causes an electronic absorption to be broad. while the spectrum of solution B contained absorptions at λmax = 230 and 365 nm. the value of λmax depends on concentration. Electronic transitions are always localized on a single atomic centre. The colour of the solution is: green. An electronic absorption includes vibrational and rotational structure.98 × 10 –4 mol dm–3. colourless. purple. water. Of the compounds given below. The difference in the spectra was because: εmax for the absorption at 365 nm is much smaller than εmax of the band at 230 nm. . ethanol. and solution B was 1. buta-1. Correct Answer: Vacuum-UV. 8. 10. In which region of the electromagnetic spectrum does an absorption at 600 nm come? Your Answer: Infrared. and the absorption spectrum is recorded. How do values of λmax for the π*←π transitions vary among a series of conjugated polyenes? Your Answer: Values vary but in no particular pattern. What does the notation ζ*←n mean? Your Answer: Emission.Results for: "Multiple choice questions" 1. What is a red shift? Your Answer: (blank) 7. The absorptions have characteristic λmax and εmax values. Correct Answer: Hepta-1. What are the correct units of εmax? –3 Your Answer: cm mol dm 3 –1 –1 Correct Answer: dm mol cm 3. Correct Answer: A group of atoms in a compound responsible for the absorption of electromagnetic radiation. 4. In which region of the electromagnetic spectrum does an absorption at 177 nm come? Your Answer: Visible. What is a chromophore? Your Answer: A coloured compound. Correct Answer: Absorption.6-diene. 5. .3-diene. Lycopene (λmax = 469 nm) is present in tomatoes. What colour of light does lycopene absorb? Your Answer: Blue. Which of the following is the principal chromophore in an azo-dye? Your Answer: C=N Correct Answer: N=N 9.001 mol dm–3 NiSO4 is placed in an optical cell of pathlength 1 cm. Correct Answer: Visible. 6. A solution of 0. Correct Answer: Values shift to longer wavelength as the number of C=C double bonds increases. 2. transition from a non-bonding MO to ζ* MO. transition from a non-bonding MO to ζ* MO. In which of the following are the π-electrons not delocalized? Your Answer: Buta-1. Two solutions of the same compound were made up. 17. The electronic spectrum of solution A contained one absorption at λmax = 230 nm. Solution A was of concentration 0. The colour of the solution is: Your Answer: orange. Using a curved piece of metal to block an opponents attack Putting metal around an Rf source When the magnetic moment of an atom blocks the full induced magnetic field from surrounding nuclei .3-diene? Your Answer: Both have four π MOs. 18. Which is the odd one out? Your Answer: SMe Correct Answer: Me 12.3-diene.indiabix. 15.com/biochemistry/nmr-spectroscopy/ 1. and solution B was 1.66 × 10–2 mol dm–3. All but one of the following groups can donate a lone pair of electrons into the carbon π-system of a conjugated polyene. while the spectrum of solution B contained absorptions at λmax = 230 and 365 nm.98 × 10–4 mol dm–3. ===================== http://www. An aqueous solution of a dye has a strong absorption with λmax= 464 nm. Which statement is incorrect about the allyl anion and buta-1. Which of the following arrangements of carbon-carbon double bonds along the backbone of a polyene does not correspond to a conjugated system? Your Answer: –C=C–C=C–C=C–C=C– Correct Answer: –C=C–C–C=C– 14. B. What is shielding in NMR? A. 13. C. X is most likely to be: Your Answer: buta-1. The difference in the spectra was because: Your Answer: electronic spectroscopic data are not always reproducible.11. Which of the following absorption maxima is not in the visible range of the electronic spectrum? Your Answer: λmax = 550 nm Correct Answer: λmax = 250 nm 16. Which of the following statements is consistent with an electronic absorption being broad? Your Answer: An electronic absorption includes vibrational and rotational structure. Of the compounds given below. A compound X is characterized in its electronic spectrum by an absorption with λmax = 217 nm (εmax = 21 000 dm3 mol–1 cm–1). Correct Answer: εmax for the absorption at 365 nm is much smaller than εmax of the band at 230 nm. with the help of wavelength spectrum .D. C. Blocking parts of a molecule from Rf radiation Answer & Explanation Answer: Option C 2. Coupling causes the peaks in 1H NMR spectra to be split into A. all the random spins of the nuclei A. C. Hydrogen Ice Dry ice Liquid helium Answer & Explanation Answer: Option D 3. B. What is used to cool the superconducting coil? A. When placed in a magnetic field. D. D. D. B. stop reverse direction align with the magnetic field rotate to 90° away from the induced field Answer & Explanation Answer: Option C 5. B. Better understanding of the nuclei is possible. plus one Answer & Explanation Answer: Option D 4. two peaks multiple peaks equal to the number of hydrogens on surrounding atoms multiple peaks equal to the number of surrounding carbon atoms multiple peaks equal to the number of hydrogen on surrounding atoms. C. A. Why is it important to use a deuterated solvent? A. C. are attached to carbon resonate at about the same frequency as carbon Answer & Explanation Answer: Option B 7. D.B. All hydrogen atoms A. B. D. with the help of frequencies ranges with the help of a mathematical translator called the fourier transfer algorithm none of the above Answer & Explanation Answer: Option C 6. have the same resonance frequency resonate at different frequencies depending on their environment. NMR uses least of this solvent So the spectrometer can lock onto the sample to prevent the spectrum from drifting during aquisition Expensive solvents work best with NMR They dissolve polymer the fastest Answer & Explanation Answer: Option B . D. B. C. C. All protons assume a random orientation 3 Which of the following statements about the energy of an applied magnetic field is FALSE? A) B) C) D) This energy can “flip” a proton from alignment with the field to alignment opposite the field. Some protons align with the field and some align opposite to it.mcgraw-hill. Nuclei are “in resonance” when they absorb this energy. When a proton is aligned with the magnetic field. This energy is proportional to the magnetic field strength. All protons align opposite to the field.http://highered.html Multiple Choice Quiz 1 Which of the following statements is FALSE about the NMR experiment. 2 When an external magnetic field is applied. its energy is lower than when it is aligned against the magnetic field. This energy is supplied by radiation in the visible region of the spectrum. When energy absorption occurs. the nuclei are said to be in resonance with the electromagnetic radiation. 4 Which of the following compounds has the MOST deshielded protons? A) B) C) D) CH3Cl CH3I CH3Br CH4 5 Which of the following compounds has the MOST deshielded methyl protons? A) B) C) tetramethylsilane methyl fluoride methanol methylamine . A) B) C) D) The energy required to flip the spin of a proton is in the infrared region of the electromagnetic spectrum. what happens to the protons in a sample? A) B) C) D) All protons align with the field. The energy difference between the two spin states depends on the strength of the magnetic field.com/sites/0072397462/student_view0/chapter15/multiple_choice_quiz. Which of the following corresponds to molecule A? B) C) . CH3CH2CH3 CH3OCH2CH3 Cl2CHCH2CH3 ClCH2CH2CH3 a b c d A) B) C) D) b>c>a>d b>c>d>a c>b>a>d c>b>d>a 9 How many signals would the following molecule show in its 1 H NMR spectrum? A) B) C) D) 5 1 6 8 10 An unknown molecule A has 4 signals in the A) 1 H NMR spectrum.18 x 108 Hz 8 Arrange the following compounds in order of decreasing chemical shift for the underlined hydrogens (largest  value first.0 ppm 7 The chemical shift of the protons in acetone is 2.06.66 ppm 16. How many hertz downfield from TMS will the resonance appear in a spectrum taken on a spectrometer operating at 300 MHz? A) B) C) D) 300 Hz 618 Hz 3000 Hz 6.0 ppm 4.6 ppm 6. smallest value last).D) 6 What is the value of the chemical shift  for an absorption at 1800 Hz from tetramethylsilane (TMS) using an NMR spectrometer with an operating frequency of 300 MHz? A) B) C) D) 1. d .D) 11 How many nonequivalent protons does the following structure have? A) B) C) D) 12 8 6 4 12 How many nonequivalent protons does the following structure have? A) B) C) D) 6 5 4 3 13 How many sets of protons are equivalent in meta-xylene (1. d. s d.3-dimethylbenzene)? A) B) C) D) 2 3 4 5 14 Reading from left to right. s. s s. what multiplicity would be found for the three nonequivalent sets of protons in the following compound? 1 H NMR spectrum of the A) B) C) s. d. 1 H NMR spectrum of C5H8O2:  1. d=2 a =2. c=2. 2H)  4.40 (triplet.26 (triplet. d=1 a=2. quintet. s. quartet. d=1 a=2. c=1. 4H) 2. 2H) A) B) C) D) 19 Which 1 H NMR spectrum represents the following compound? . b=7.D) s. d 15 What is the splitting pattern of the methylene protons in propane? A) B) C) D) triplet quartet doublet septet 16 The signal for the methylene protons of butane is split into a A) B) C) D) doublet. b=8. triplet. d=2 18 Propose a structure for the following compound. A) B) C) D) a=2. 17 Give the number of lines in the coupling pattern for each type of hydrogen. b=7. c=7.90 (multiplet.c=8. b=8. what is the structure of compound A? A) B) C) D) 21 The 1 H NMR spectrum of a compound is shown below.90 (quartet.20 (quartet. 2H) 1 H NMR spectrum  1. 3H)  1.28 (triplet. 1H) 1 H NMR spectrum  1.00 (triplet. 1H)  4.50 (triplet. 2H)  3.28 (triplet.90 (quintet. 1H)  5. 4H) 1 20 An unknown compound A has the molecular formula C H O . 1H) 1 H NMR spectrum  1. 4H)  3.00 (triplet. 2H)  2.80 (septet.50 (doublet. 1H)  2. What is the structure of the compound? . 2H)  2. Based on the following 4 8 2 H NMR spectrum.50 (triplet.00 (quartet.1 A) B) C) D) H NMR spectrum  0. 23 There are several compounds with the molecular formula C H 5 10Br2.2-dimethylpropane.A) B) C) D) 22 A compound of formula C H 5 12 gives 1 signal in the 1H NMR and 2 signals in the 13 C NMR. The compound is A) B) C) D) pentane.3 (1H. 2. Cannot tell without more information. Which isomer a–d with this formula has the following 1H NMR spectrum?  (ppm) 1. 2-methylbutane. singlet) A) B) a b .0 (9H. singlet) 5. C) D) c d 24 How many methyl peaks would you expect to observe in the A) B) C) D) 1 2 3 4 1 H NMR spectrum of cis-1.4-dimethylcyclohexane? 25 How many absorption bands will appear in the 13 C NMR spectrum for the following compound? A) B) C) D) 4 6 7 8 26 How many absorption bands will appear in the 13 C NMR spectrum for the following compound? A) B) C) D) 6 7 8 9 27 How many absorption bands will appear in the 13 C NMR spectrum for the following compound? A) B) C) D) 5 7 8 9 28 How many resonances in the 13 C NMR spectrum would the following structure show? . mass spectroscopy data.9 (multiplet. and IR spectrum.30 (triplet. Mass Spectrum: m/e: 222 177 149 Intensity: (as % of base peak) 10% 38% 100% IR Spectrum: Intensity (peak): s m m s m-w m-w m m m s Frequency (cm–1): 3100 2900 2800 1740 1600 1475 1465 1450 1375 1300–1000 A) .4–7.A) B) C) D) 8 6 4 2 29 How many signals are expected in a A) B) C) D) 4 5 6 7 13 C NMR spectrum of methylcyclohexane? 30 Deduce the structure of an unknown compound using the following 1 1 H NMR spectrum: 1.29 (quartet. 6H) 4. 4H) H NMR spectrum. 4H)  7. 6 correct (20%) 22 incorrect (73%) 2 unanswered (7%) Your Results: The correct answer for each question is indicated by a . for a final grade of 20%. C)When energy absorption occurs.B) C) D) Multiple Choice Quiz Results Reporter Out of 30 questions. A)The energy required to flip the spin of a proton is in the infrared region of the electromagnetic spectrum. 1 INCORRECT Which of the following statements is FALSE about the NMR experiment. D)When a proton is aligned with the magnetic field. B)The energy difference between the two spin states depends on the strength of the magnetic field. the nuclei are said to be in resonance with the electromagnetic radiation. . you answered 6 correctly. its energy is lower than when it is aligned against the magnetic field. 4 CORRECT Which of the following compounds has the MOST deshielded protons? A)CH3Cl B)CH3I C)CH3Br D)CH4 5 INCORRECT Which of the following compounds has the MOST deshielded methyl protons? A)tetramethylsilane B)methyl fluoride . C)Some protons align with the field and some align opposite to it. B)Nuclei are “in resonance” when they absorb this energy.2 CORRECT When an external magnetic field is applied. C)This energy is proportional to the magnetic field strength. what happens to the protons in a sample? A)All protons align with the field. D)This energy is supplied by radiation in the visible region of the spectrum. B)All protons align opposite to the field. D)All protons assume a random orientation 3 INCORRECT Which of the following statements about the energy of an applied magnetic field is FALSE? A)This energy can “flip” a proton from alignment with the field to alignment opposite the field. 66 ppm B)16. How many hertz downfield from TMS will the resonance appear in a spectrum taken on a spectrometer operating at 300 MHz? A)300 Hz B)618 Hz C)3000 Hz D)6.06.C)methanol D)methylamine 6 UNANSWERED What is the value of the chemical shift  for an absorption at 1800 Hz from tetramethylsilane (TMS) using an NMR spectrometer with an operating frequency of 300 MHz? A)1.18 x 108 Hz Arrange the following compounds in order of decreasing chemical shift for the underlined hydrogens (largest  value first.0 ppm D)4.6 ppm C)6.0 ppm 7 INCORRECT The chemical shift of the protons in acetone is 2. 8 CORRECT CH3CH2CH3 CH3OCH2CH3 Cl2CHCH2CH3 ClCH2CH2CH3 a b c d A)b > c > a > d B)b > c > d > a C)c > b > a > d D)c > b > d > a . smallest value last). How many signals would the following molecule show in its 1H NMR spectrum? 9 INCORRECT A)5 B)1 C)6 D)8 10 CORRECT An unknown molecule A has 4 signals in the 1H NMR spectrum. Which of the following corresponds to molecule A? A) B) C) D) How many nonequivalent protons does the following structure have? 11 INCORRECT A)12 . what multiplicity would be found for the three nonequivalent sets of protons in the 1H NMR spectrum of the following compound? 14 INCORRECT .B)8 C)6 D)4 How many nonequivalent protons does the following structure have? 12 CORRECT A)6 B)5 C)4 D)3 How many sets of protons are equivalent in meta-xylene (1.3-dimethylbenzene)? 13 UNANSWERED A)2 B)3 C)4 D)5 Reading from left to right. d=1 . B)triplet. C)quartet. D)quintet. d D)s. d. s B)d. d 15 CORRECT What is the splitting pattern of the methylene protons in propane? A)triplet B)quartet C)doublet D)septet 16 INCORRECT The signal for the methylene protons of butane is split into a A)doublet. s. b=7. s. 17 INCORRECT A)a=2. s C)s. Give the number of lines in the coupling pattern for each type of hydrogen.A)s. c=1. d. 50 (triplet. 2H)  4. 1H) .28 (triplet.80 (septet.90 (quartet.40 (triplet.26 (triplet. 2H)  3.B)a=2. d=1 C)a=2. 1H)  4.90 (multiplet. d=2 D)a =2. b=8. 2H) A) B) C) D) Which 1H NMR spectrum represents the following compound? 19 INCORRECT A)1H NMR spectrum  0.00 (triplet.c=8. 4H) 2.50 (triplet. c=7. 2H)  2. b=7. 1 H NMR spectrum of C5H8O2:  1. 1H)  5. c=2. d=2 18 INCORRECT Propose a structure for the following compound. b=8.50 (doublet. 1H) B)1H NMR spectrum  1. 4H)  3. C)1H NMR spectrum  1.00 (triplet, 3H)  1.20 (quartet, 1H)  2.00 (quartet, 2H) D)1H NMR spectrum  1.90 (quintet, 2H)  2.28 (triplet, 4H) An unknown compound A has the molecular formula C 4H8O2. Based on the following 1H NMR spectrum, what is the structure of compound A? 20 INCORRECT A) B) C) D) 21 INCORRECT The 1H NMR spectrum of a compound is shown below. What is the structure of the compound? A) B) C) D) 22 INCORRECT A compound of formula C5H12 gives 1 signal in the 1H NMR and 2 signals in the 13 C NMR. The compound is A)pentane. B)2-methylbutane. C)2,2-dimethylpropane. D)Cannot tell without more information. There are several compounds with the molecular formula C 5H10Br2. Which isomer a–d with this formula has the following 1H NMR spectrum?  (ppm) 1.0 (9H, singlet) 5.3 (1H, singlet) 23 INCORRECT A)a B)b C)c D)d 24 INCORRECT How many methyl peaks would you expect to observe in the 1H NMR spectrum of cis-1,4-dimethylcyclohexane? A)1 B)2 C)3 D)4 How many absorption bands will appear in the 13 C NMR spectrum for the following compound? 25 INCORRECT A)4 B)6 C)7 D)8 How many absorption bands will appear in the 13 C NMR spectrum for the following compound? 26 INCORRECT A)6 B)7 C)8 D)9 How many absorption bands will appear in the 13 C NMR spectrum for the following compound? 27 INCORRECT A)5 B)7 C)8 D)9 28 INCORRECT How many resonances in the 13 C NMR spectrum would the following structure show? . 4–7.30 (triplet. 6H) 4.9 (multiplet. 4H) Mass Spectrum: 30 INCORRECT m/e: 222 177 149 Intensity: (as % of base peak) 10% 38% 100% IR Spectrum: Intensity (peak): Frequency (cm–1): .29 (quartet. 4H)  7.A)8 B)6 C)4 D)2 29 INCORRECT How many signals are expected in a 13 C NMR spectrum of methylcyclohexane? A)4 B)5 C)6 D)7 Deduce the structure of an unknown compound using the following 1H NMR spectrum. 1 H NMR spectrum: 1. and IR spectrum. mass spectroscopy data. mcgraw-hill.s m m s m-w m-w m m m s 3100 2900 2800 1740 1600 1475 1465 1450 1375 1300–1000 A) B) C) D) http://highered.com/sites/0072397462/student_view0/chapter14/ 14 Mass Spectrometry and Infrared Spectroscopy . conjugation. This peak is due to which of the following? A) B) C) D) capture of an H atom presence of a presence of a 13 C Cl 36 capture of a proton 2 Infrared spectroscopy provides valuable information about A) B) C) D) molecular weight.9949 6 Deduce the structure of an unknown compound with molecular formula C H 5 12O using information given by its infrared spectrum. but all peaks in the mass spectrum of chlorobenzene are accompanied by a smaller peak one mass unit higher. functional groups. O. 15. 1.9949) of the molecular ion of a compound with molecular formula C3H8O? A) B) C) D) 60. 14. 12. N. 3 A strong signal at 1700 cm A) B) C) D) alcohol ether carbonyl amine –1 in an IR spectrum indicates the presence of a(n) 4 A strong signal at 3400 cm A) B) C) D) alcohol ether carbonyl amine –1 in an IR spectrum indicates the presence of a(n) 5 What is the exact mass (in atomic mass units: C.0031.0000.0000 60. melting point.0573 60. H.0624 59. Intensity (peak): Frequency (cm–1): m m m m 3300 2900 2800 1465 .0078.Multiple Choice Quiz 1 Not only the molecular ion peak. 3 3 Intensity (peak): Frequency (cm-1): m m-w m m m s 3300 2225 2800 1450 1375 667 A) B) C) D) 8 Deduce the structure of an unknown compound with molecular formula C H 9 10O using information given by its infrared spectrum.m m 1450 1375 A) B) C) D) 7 Deduce the structure of an unknown compound with molecular formula C H Br using information given by an infrared spectrum. Intensity (peak): Frequency (cm–1): s m m s m-w m-w m m m 3100 2900 2800 1710 1600 1475 1465 1450 1375 A) B) C) . 5 8 Intensity (peak): Frequency (cm–1): m m s m-w m m 3100 2800 1705 1640 1450 1375 A) B) C) D) 10 Which of the following bonds would be expected to have the highest frequency stretch? A) B) C) D) carbon–carbon single bond carbon–carbon double bond carbon–carbon triple bond carbon–bromine single bond 11 Which of the following bonds would be expected to have the lowest frequency stretch? A) B) C) D) C –I C–Br C–Cl C –F 12 Which of the following compounds a–d has an IR absorption at 1640 cm –1 ? A) B) C) a b c .D) 9 Deduce the structure of an unknown compound with molecular formula C H O using information given by its infrared spectrum. D) d 13 Which of the following compounds a–d has an IR absorption at 3300 cm –1 ? A) B) C) D) a b c d Results Reporter Your Results: The correct answer for each question is indicated by a . C)conjugation. . 1 INCORRECT Not only the molecular ion peak. D)functional groups. but all peaks in the mass spectrum of chlorobenzene are accompanied by a smaller peak one mass unit higher. B)melting point. This peak is due to which of the following? A)capture of an H atom B)presence of a 13 C C)presence of a 36 Cl D)capture of a proton 2 INCORRECT Infrared spectroscopy provides valuable information about A)molecular weight. 3 –1 INCORRECT A strong signal at 1700 cm in an IR spectrum indicates the presence of a(n) A)alcohol B)ether C)carbonyl D)amine 4 –1 INCORRECT A strong signal at 3400 cm in an IR spectrum indicates the presence of a(n) A)alcohol B)ether C)carbonyl D)amine 5 INCORRECT What is the exact mass (in atomic mass units: C.9949 Deduce the structure of an unknown compound with molecular formula C 5H12O using information given by its infrared spectrum.0624 D)59. 1. 14. 6 INCORRECT Intensity (peak): Frequency (cm–1): m 3300 .0573 C)60. 12. O. 15.0078. N.9949) of the molecular ion of a compound with molecular formula C3H8O? A)60. H.0000.0031.0000 B)60. m m m m m 2900 2800 1465 1450 1375 A) B) C) D) Deduce the structure of an unknown compound with molecular formula C 3H3Br using information given by an infrared spectrum. Intensity (peak): Frequency (cm-1): m m-w m m m s 3300 2225 2800 1450 1375 667 7 INCORRECT A) B) C) . Intensity (peak): Frequency (cm–1): s m m 3100 2900 2800 1710 1600 1475 1465 1450 1375 8 INCORRECT s m-w m-w m m m A) B) C) D) 9 INCORRECT Deduce the structure of an unknown compound with molecular formula C 5H8O using information given by its infrared spectrum. .D) Deduce the structure of an unknown compound with molecular formula C 9H10O using information given by its infrared spectrum. Intensity (peak): Frequency (cm–1): m m s m-w m m 3100 2800 1705 1640 1450 1375 A) B) C) D) 10 INCORRECT Which of the following bonds would be expected to have the highest frequency stretch? A)carbon–carbon single bond B)carbon–carbon double bond C)carbon–carbon triple bond D)carbon–bromine single bond 11 INCORRECT Which of the following bonds would be expected to have the lowest frequency stretch? A)C–I . B)C–Br C)C–Cl D)C–F Which of the following compounds a–d has an IR absorption at 1640 cm–1? 12 INCORRECT A)a B)b C)c D)d Which of the following compounds a–d has an IR absorption at 3300 cm–1? 13 INCORRECT A)a B)b C)c D)d ========== . The path of ions after deflection depends on. detection. detection acceleration.org.uk/sci_htm_files/mcspec. detection 2. Which one of the following statements about ionisation in a mass spectrometer is incorrect? gaseous atoms are ionised by bombarding them with high energy electrons atoms are ionised so they can be accelerated atoms are ionised so they can be deflected it doesn't matter how much energy you use to ionise the atoms 3.knockhardy. The correct order for the basic features of a mass spectrometer is. deflection... deflection. only the mass of the ion only the charge on the ion both the charge and the mass of the ion neither the charge nor the mass of the ion . deflection. ionisation. ionisation ionisation. acceleration.. deflection..http://www. ionisation. detection acceleration.HTM SPECTROSCOPY MULTIPLE CHOICE QUESTIONS 1. acceleration. 4. Which of the following is not a use for mass spectrometry? calculating the isotopic abundance in elements investigating the elemental composition of planets confirming the presence of O-H and C=O in organic compounds calculating the molecular mass of organic compounds 6. Which one of the following pieces of information cannot be obtained from an infra-red spectrum? . Which one of the following statements about the mass spectrum of CH3Br is correct? the last two peaks are of equal size and occur at m/z values of 94 and 96 the last two peaks have abundances in the ratio 3:1 and occur at m/z values of 94 and 96 there is just one peak for the molecular ion with an m/z value of 95 there is just one peak for the molecular ion with an m/z value of 44 7. Which of the following species will be deflected to the greatest extent? 37 Na+ 35 Na+ 37 Na 35 Na2+ 5. .. The region of an infra-red spectrum where many absorptions take place is known as the.. organic compounds contain carbon atoms organic compounds are mostly covalent hydrogen atoms are found in nearly all organic compounds organic compounds have low boiling points . thumbprint region handprint region footprint region fingerprint region 10. check that the IR spectrum has absorptions at 3500cm-1 and 1650cm-1 check that the IR spectrum has no absorption around 3500cm-1 check that the IR spectrum has no absorption around 1650cm-1 check that the IR spectrum no absorptions at 3500cm-1 and 1650cm-1 9.the molecular mass the presence of C=O bonds the presence of O-H bonds the identity of a compound through comparison with other spectra 8.... Proton nmr is useful for investigating the structure of organic compounds because. To check that a secondary alcohol has been completely oxidised to a ketone you can. Signals in a proton nmr spectrum do not provide information about.. two doublets and a sextet a doublet and a septet .. the relative number of hydrogen atoms in a particular environment the number of chemically different hydrogen atoms on adjacent atoms the environment of different hydrogen atoms in a molecule the molecular mass of an organic molecule 13... a triplet and a singlet a triplet and a quartet a doublet and a sextet a triplet and a septet 14.11. The proton nmr spectrum of propane will consist of... The proton nmr of 1-bromopropane will consist of. Which of the following statements about tetramethylsilane is incorrect? it produces a single peak at =10 it is inert it is volatile and can be easily distilled off and used again it is used to provide a reference against which other peaks are measured 12. three quartets and a singlet two doublets and a singlet two singlets one singlet 17... a doublet and a triplet 16. a doublet and a triplet a singlet.... The proton nmr of 2-bromopropane will consist of. a doublet and a triplet two triplets and a sextet 15. two doublets and a sextet a doublet and a septet a singlet. counting the number of chemically equivalent hydrogen atoms on adjacent atoms counting the number of chemically different hydrogen atoms on adjacent atoms counting the number of chemically different hydrogen atoms on adjacent atoms and adding 1 counting the number of chemically different hydrogen atoms on adjacent atoms and subtracting 1 . The splitting pattern for a signal is found by.a singlet.. The proton nmr of 2-bromo-2-methylpropane will consist of. 1:1:1 1:2:1 1:3:1 1:4:1 21. two singlets a triplet and a doublet two doublets a singlet and a doublet 20. the relative peak areas are in the ratio. In a triplet. an infra red absorption at 1650cm-1 and just one singlet in its nmr spectrum? butane CH3COCH3 ..18.. Which compound has a molecular ion at m/z = 58. The molecule HOCH2CH2OH will have an nmr spectrum consisting of.. Which one of the following statements about protons on O-H groups is incorrect? they always produce a doublet they always produce a singlet they are not taken into account when working out splitting patterns of adjacent protons their signal can be removed from its normal location by shaking with deuterium oxide 19.. infra red spectrum mass spectrum proton nmr spectrum boiling point . The isomer of C4H8 which produces an nmr spectrum with four different signals is... To work out the molecular mass of an organic molecule you would look at its.. CH2=CHCH2CH3 CH3CH=CHCH3 it produces two signals (CH3)2C=CH2 it produces two signals cyclobutane it produces just one signal 24. Which one of the following hydrocarbons produces an nmr spectrum with more than one peak? methane ethane butane cyclobutane Correct.. there are two peaks 23.CH3CH2CHO 2-methylpropane 22. ignou.8 Summary.Quick View Representation of NMR...7 Applications of NMR Spectroscopy. 12../6/. Qualitative Applications..in/wiki/images/6/69/Unit_12_NMR_Spectrometry.pd.ignou.in/wiki/.Vedyadhara vedyadhara..../Unit_12_NMR_Spectrometry.pdf . 12.. Which one of the following methods would be best for finding the identity of an organic compound? finding the m/z value of the molecular ion in its mass spectrum its proton nmr spectrum comparing its infra red spectrum with known examples measuring its melting point --------================= PDF] UNIT 12 NMR SPECTROSCOPY .ac. Quantitative Applications.25. 12. http://vedyadhara.9 Terminal Questions . File Format: PDF/Adobe Acrobat .ac.