Chapter NineMULTIPLE CHOICE QUESTIONS Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Easy 1. How many signals would you expect to find in the 1H NMR spectrum of CH3OCH2CH2OCH3? A) 1 B) 2 C) 3 D) 4 E) 5 Ans: B Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Easy 2. Predict the splitting pattern you would observe for the proton at C1 of 2,3-dimethyl-2phenylbutane. A) B) C) D) E) Doublet Singlet Quartet Septet Octet Ans: B 33 Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 3. Which one of the following best represents the predicted approximate chemical shift and coupling for the hydrogen(s) indicated with the arrow? O CH3 A) B) C) D) E) 1.10 ppm, singlet 2.10 ppm, doublet 3.40 ppm, singlet 4.5 ppm, singlet 3.5 ppm, quartet Ans: C Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 4. Which one of the following best represents the predicted approximate chemical shift and coupling for the hydrogen(s) indicated with the arrow? O A) B) C) D) E) 1.00 ppm, singlet 2.10 ppm, singlet 2.10 ppm, quartet 3.00 ppm, singlet 2.10 ppm, triplet Ans: B 34 Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 5. Which one of the following best represents the predicted approximate chemical shift and coupling for the hydrogen(s) indicated with the arrow? O A) B) C) D) E) 1.00 ppm, quartet 2.40 ppm, singlet 2.40 ppm, quartet 3.00 ppm, quartet 2.40 ppm, triplet Ans: C Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 6. Which one of the following best represents the predicted approximate chemical shift and coupling for the hydrogen(s) indicated with the arrow? O A) B) C) D) E) 1.00 ppm, quartet 2.40 ppm, singlet 2.40 ppm, quartet 3.00 ppm, quartet 1.00 ppm, triplet Ans: E 35 Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 7. Which one of the following best represents the predicted approximate chemical shift and coupling for the hydrogen(s) indicated with the arrow? H H A) B) C) D) E) 5.40 ppm, multiplet 2.00 ppm, multiplet 2.00 ppm, doublet 2.00 ppm, quartet 5.40 ppm, doublet Ans: A Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 8. Which one of the following best represents the predicted approximate chemical shift and coupling for the hydrogen(s) indicated with the arrow? H H A) B) C) D) E) 5.40 ppm, doublet 1.00 ppm, multiplet 2.00 ppm, doublet 1.00 ppm, doublet 5.40 ppm, multiplet Ans: D 36 Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 9. Which one of the following best represents the predicted approximate chemical shift and coupling for the hydrogen(s) indicated with the arrow? N A) B) C) D) E) 3.00 ppm, doublet 3.00 ppm, triplet 5.00 ppm, triplet 1.00 ppm, doublet 5.40 ppm, multiplet Ans: B Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 10. Which one of the following best represents the predicted approximate chemical shift and coupling for the hydrogen(s) indicated with the arrow? N A) B) C) D) E) 3.00 ppm, doublet 3.00 ppm, triplet 5.00 ppm, triplet 1.00 ppm, doublet 3.00 ppm, singlet Ans: E 37 Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 11. For the following compound how many different signals would you see in the proton NMR? (Assume that you can see them all.) A) B) C) D) E) 4 5 6 7 8 Ans: A Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 12. For the following compound how many different signals would you see in the proton NMR? (Assume that you can see them all.) H3CO A) B) C) D) E) 4 5 6 7 8 Ans: C 38 Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 13. For the following compound how many different signals would you see in the proton NMR? (Assume that you can see them all.) A) B) C) D) E) 1 2 3 4 5 Ans: C Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 14. A downfield (δ 9-10) singlet is observed in the 1H NMR spectrum of: O A) B) C) D) E) CH3CCH2CH3 H C6H5CH2C H (CH3)2CHC H (CH3)3CC O O O O C6H5CH2CCH3 Ans: D 39 Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Medium 15. For the following compound how many different signals would you see in the proton NMR? (Assume that you can see them all.) A) B) C) D) E) 1 2 3 4 5 Ans: D Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Medium 16. For the following compound how many different signals would you see in the proton NMR? (Assume that you can see them all.) O A) B) C) D) E) 4 5 6 7 8 Ans: B 40 Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Medium 17. Which one of the following best represents the predicted approximate chemical shift and coupling for the hydrogen(s) indicated with the arrow? O CH3 A) B) C) D) E) 1.10 ppm, singlet 2.10 ppm, triplet 3.40 ppm, triplet 4.5 ppm, singlet 5.3 ppm, doublet Ans: D Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Medium 18. Predict the splitting pattern you would observe for the proton at C4 of 2,3-dimethyl-2phenylbutane. A) B) C) D) E) Doublet Singlet Quartet Septet Octet Ans: A 41 Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Medium 19. A) B) C) D) E) How many 1H NMR signals would trans-1,2-dichlorocyclopropane give? 1 2 3 4 5 Ans: B Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Medium 20. How many chemically distinct 1H NMR signals are there in the following compound? ClCH2CHCH3 A) B) C) D) E) Br 1 2 3 4 5 Ans: D Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Medium 21. A) B) C) D) E) How many 1H NMR signals would cis-1,2-dichlorocyclopropane give? 1 2 3 4 5 Ans: C 42 Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Medium How many 1H NMR signals would you expect from this compound? 22. OCH3 OCH3 A) B) C) D) E) 1 2 3 4 5 Ans: B Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Medium 23. The 1H NMR spectrum of which of these compounds would consist of a triplet, singlet and quartet only? A) 2-chloro-4-methylpentane B) 3-chloro-2-methylpentane C) 3-chloropentane D) 1-chloro-2,2-dimethylbutane E) 3-chloro-3-methylpentane Ans: E Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Medium 24. Which one of the following best represents the predicted approximate chemical shift and coupling for the hydrogen(s) indicated with the arrow? H H A) B) C) D) E) 1.00 ppm, doublet 2.00 ppm, singlet 2.00 ppm, triplet 2.00 ppm, doublet 1.00 ppm, triplet Ans: D 43 Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Medium 25. A) B) C) D) E) A compound C5H11Cl which exhibits only two singlets in the 1H NMR spectrum must be: 1-Chloropentane 1-Chloro-2,2-dimethylpropane 1-Chloro-2-methylbutane 3-Chloropentane 1-Chloro-3-methylbutane Ans: B Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Medium 26. Consider the expected 1H NMR spectrum of 1,1,3,3-tetramethylcyclopentane. Which of the following is likely to be observed? A) B) C) D) E) 7 signals: all singlets 7 signals: 4 singlets, 3 doublets 3 signals: all singlets 3 signals: one singlet, 2 doublets 3 signals: two singlets, one doublet Ans: C Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Medium 27. Consider the expected 1H NMR spectrum of 2,4-dimethyl-1,4-pentadiene. Which of the following is likely to be observed? A) B) C) D) E) 7 signals: all singlets 4 signals: all singlets 3 signals: all singlets 3 signals: one singlet, 2 doublets 4 signals: two singlets, two doublets Ans: E Topic: Proton NMR- Symmetry, Splitting, Chemical Shift 44 Section: 9.2 Difficulty Level: Hard 28. For the C2 methylene group in 1-bromopropane, the theoretical multiplicity in the 1H NMR spectrum, presuming that Jab is sufficiently different from Jbc and that the instrument has sufficient resolving power, is which of these? CH3 CH2 CH2 Br c b a A) B) C) D) E) 2 5 6 8 12 Ans: E Topic: Structure Elucidation Section: 2.16, 9.2 Difficulty Level: Medium 29. An organic compound absorbs strongly in the IR at 1687 cm-1. Its 1H NMR spectrum consists of two signals, a singlet at 2.1 ppm and a multiplet centered at 7.1 ppm. Its mass spectrum shows significant peaks at m/z 120, m/z 105 and m/z 77. This information is consistent with which of the following structures? O O O I II III A) B) C) D) E) I II III IV V Ans: A IV V Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2A 45 Difficulty Level: Easy 30. If all the protons of 1-fluoropentane could be discerned, which would you expect to be at the lowest field in the 1H NMR spectrum of this compound? CH3CH2CH2CH2CH2F V IV III II I Protons on carbon I Protons on carbon II Protons on carbon III Protons on carbon IV Protons on carbon V Ans: A A) B) C) D) E) Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2A Difficulty Level: Hard 31. The 1H NMR signal for which of the indicated protons occurs farthest downfield? III Cl H H H C C C I II C CH3 IV V A) B) C) D) E) I II III IV V Ans: E Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2C 46 Difficulty Level: Easy 32. Which proton(s) of the compound below would appear as a septet in the 1H NMR spectrum? I CH3 CH3CH2CH2-O-CH CH3 V IV III II I A) The protons on carbon I B) The protons on carbon II C) The protons on carbon III D) The protons on carbon IV E) The protons on carbon V Ans: B Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2C Difficulty Level: Easy 33. Which proton(s) of the compound below would appear as a doublet in the 1H NMR spectrum? I CH3 CH3CH2CH2-O-CH CH3 V IV III II I A) The protons on carbon I B) The protons on carbon II C) The protons on carbon III D) The protons on carbon IV E) The protons on carbon V Ans: A Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2C 47 Difficulty Level: Easy 34. Which proton(s) of the compound below would appear as a triplet in the 1H NMR spectrum? I CH3 CH3CH2CH2-O-CH CH3 V IV III II I A) The protons on carbon II B) The protons on carbon I and V C) The protons on carbon III and V D) The protons on carbon III and IV E) The protons on carbon V Ans: C Topic: Proton NMR- Symmetry, Splitting, Chemical shift Section: 9.2C Difficulty Level: Easy 35. Consider the expected splitting of signal “b” in the 1H NMR spectrum of 1-methoxy-2methylpropane, shown below. Presuming that Jab is sufficiently different from Jbc and that the instrument has sufficient resolving power, what is the theoretical multiplicity of signal “b”? a a A) B) C) D) E) 8 9 12 21 24 Ans: D b O c d Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2C 48 Difficulty Level: Medium 36. Predict the splitting pattern you would observe for the proton at C3 of 2,3-dimethyl-2phenylbutane. A) B) C) D) E) Doublet Singlet Quartet Septet Octet Ans: D Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2C Difficulty Level: Medium 37. Which of these compounds will not be represented by a singlet only in the 1H NMR spectrum? A) Neopentane B) Hexamethylbenzene C) Isobutane D) (Z)-1,2-Dichloroethene E) (E)-1,2-Dichloroethene Ans: C Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2C Difficulty Level: Hard 38. Consider the expected splitting of the C2 proton signal in the 1H NMR spectrum of 1,1dibromopentane. Presuming that the coupling constants for neighboring protons are sufficiently different, and that the instrument has sufficient resolving power, what is the theoretical multiplicity of the C2 proton signal? A) 3 B) 4 C) 5 D) 6 E) 8 Ans: D Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2C 49 Difficulty Level: Hard 39. Consider the expected splitting of signal “b” in the 1H NMR spectrum of N-methyl-1propanamine, shown below. Presuming that Jab is sufficiently different from Jbc and that the instrument has sufficient resolving power, what is the theoretical multiplicity of signal “b”? d H b N a A) B) C) D) E) 2 5 6 8 12 Ans: E c e Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2C Difficulty Level: Hard 40. Consider the expected splitting of signal “b” in the 1H NMR spectrum of 1,1-dichloro-3methylbutane, shown below. Presuming that Jab is sufficiently different from Jbc and that the instrument has sufficient resolving power, what is the theoretical multiplicity of signal “b”? Cl a a b c d Cl A) B) C) D) E) 8 9 12 18 21 Ans: E Topic: Proton NMR- Symmetry, Splitting, Chemical shift Section: 9.2C Difficulty Level: Hard 50 41. Consider the expected splitting of signal “b” in the 1H NMR spectrum of 1,2dimethoxypropane, shown below. Presuming that Jbc is sufficiently different from Jbd and that the instrument has sufficient resolving power, what is the theoretical multiplicity of signal “b”? c a O A) B) C) D) E) 2 5 6 8 12 Ans: E b O d e Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2C Difficulty Level: Hard 42. Consider the expected splitting of signal “c” in the 1H NMR spectrum of 2-ethyl-1butanol, shown below. Presuming that Jbc is sufficiently different from Jcd and that the instrument has sufficient resolving power, what is the theoretical multiplicity of signal “c”? a b a A) B) C) D) E) 6 7 8 12 15 Ans: E b c OH d e Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2C Difficulty Level: Hard 51 43. Consider the expected splitting of the C2 proton signal in the 1H NMR spectrum of 2ethyl-1,3-propanediol. Presuming that the coupling constants for neighboring protons are sufficiently different, and that the instrument has sufficient resolving power, what is the theoretical multiplicity of the C2 proton signal? A) 6 B) 7 C) 8 D) 12 E) 15 Ans: E Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2C Difficulty Level: Hard 44. What is the theoretical multiplicity of the C-2 proton signal in the 1H NMR spectrum of 2-hydroxymethyl-1,3-propanediol, shown below? OH HO OH A) B) C) D) E) 1 6 7 8 9 Ans: C 52 Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2C Difficulty Level: Hard 45. Consider the 1H NMR spectrum of very pure 1-propanol. Assuming the maximum multiplicity of signals and non-superposition of peaks, what is the expected signal splitting pattern for each signal, in the order (a, b, c, d) ? CH3-CH2-CH2-OH a b c d A) B) C) D) E) 3, 6, 4, 1 3, 6, 4, 3 3, 12, 3, 1 3, 12, 3, 3 3, 12, 6, 3 Ans: E Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2, 9.2C Difficulty Level: Medium 46. The 1H NMR spectrum of which of the compounds below, all of formula C7H12O2, would consist of two singlets only? O O O O O O I O O II O O III A) B) C) D) E) I II III IV V Ans: E IV V 53 Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2, 9.2C Difficulty Level: Hard 47. The 1H NMR spectrum of which of the compounds below, all of formula C7H12O2, would consist of three singlets only? O O O O O O I O O II O O III A) B) C) D) E) I II III IV V Ans: B IV V Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2, 9.2C Difficulty Level: Hard 48. The 1H NMR spectrum of which of the compounds below, all of formula C7H12O2, would consist of a singlet, a doublet and a triplet only? O O O O O O I O O II O O III A) B) C) D) E) I II III IV V Ans: D IV V 54 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.2A, 9.2C Difficulty Level: Medium 49. A compound with the molecular formula C4H10O gives a 1H NMR spectrum consisting only of a quartet centered at δ 3.5 and a triplet at δ 1.1. The most likely structure for the compound is: CH3 A) CH3COH CH3 CH3 CH3OCHOH CH3CH2CH2CH2OH CH3CH2OCH2CH3 CH3CHCH2OH B) C) D) E) CH3 Ans: D 55 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Easy 50. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C9H14O? IR data shows no characteristic peak around 1700 cm-1. The 13 C-NMR chemical shifts (ppm): 108.4, 50.9, 31.6, 23.5, 2.0. Relative integration is known. 6 3 2 3 3 2 PPM 1 0 A) B) C) O O O O O O D) E) O O O O Ans: C 56 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Easy 51. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C9H10O2? Relative integration is shown. 5 2 1 2 12 10 8 PPM 6 4 2 0 A) CHO B) CO2H C) CO2H D) HO2C E) CO2H Ans: C 57 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Easy 52. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C8H14? Relative integration is shown. 9 3 2 8 7 6 5 4 PPM 3 2 1 0 A) B) C) C D) E) Ans: D 58 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Easy 53. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C6H11N? In the IR spectrum you notice a stretch at about 2250 cm-1. Relative integration is shown. 6 4 1 8 7 6 5 4 PPM 3 2 1 0 A) B) CN C) CN D) E) CN N H Ans: D 59 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 54. Determine the most likely structure of a compound, with the molecular formula C9H12, which gave a 1H NMR spectrum consisting of: a doublet at δ 1.25 a septet at δ 2.90 and a multiplet at δ 7.25 I II III IV V ] A) B) C) D) E) I II III IV V Ans: D Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 55. A compound with the molecular formula C10H13Cl gave the following 1H NMR spectrum: singlet, δ 1.6 singlet, δ 3.1 multiplet, δ 7.2 (5H) The most likely structure for the compound is: Cl Cl Cl I II Cl Cl III A) B) C) D) E) I II III IV V Ans: B IV V 60 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 56. A compound with the molecular formula C8H9BrO gave the following 1H NMR spectrum: triplet, δ 1.4 quartet, δ 3.9 multiplet, δ 7.0 (4H) There was no evidence of an -OH band in the IR spectrum. A possible structure for the compound is: O Br O Br Br O I O Br II Br O III A) B) C) D) E) I II III IV V Ans: C IV V Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 57. A compound with the molecular formula C6H15N gave the following 1H NMR spectrum: triplet, δ 0.90 quartet, δ 2.4 There were no other signals. The most likely structure for the compound is: A) CH3NCH2CH3 B) C) D) E) CH2CH2CH3 CH3NCH2CH2CH2CH3 CH3 CH3CH2CH2CH2CH2CH2NH2 CH3CH2NCH2CH3 CH2CH3 CH3CH2CH2NCH2CH2CH3 H Ans: D 61 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 58. A compound with the molecular formula C8H9ClO gave the following 1H NMR spectrum: triplet, δ 3.7 triplet, δ 4.2 multiplet, δ 7.1 There was no evidence of an -OH band in the IR spectrum. The most likely structure for the compound is: Cl O Cl O Cl O I O Cl II Cl O III A) B) C) D) E) I II III IV V Ans: A IV V Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 59. A compound with the molecular formula C3H6Cl2 gave a 1H NMR spectrum consisting only of a triplet centered at δ 3.7 and a quintet centered at δ 2.2. The most likely structure for the compound is: A) CH3CH2CHCl2 B) CH3CHClCH2Cl C) ClCH2CHClCH3 D) ClCH2CH2CH2Cl E) CH3CCl2CH3 Ans: D 62 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 60. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C10H20? Relative integration is shown. 3 2 8 7 6 5 4 PPM 3 2 1 0 A) B) C) D) E) Ans: C 63 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 61. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C4H8O? Relative integration is shown. 1 1 8 7 6 5 4 PPM 3 2 1 0 A) O B) C) D) E) O OH OH O Ans: D 64 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 62. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C7H12O4? The 13C-NMR spectrum shows peaks at 14.1, 40.8, 61.0 and 166.8 ppm. Relative integration is shown. 3 2 1 5 4 3 PPM 2 1 0 A) B) C) H O O O O O H O O O O D) O O O O O E) O O O O Ans: A 65 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 63. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C10H11N? Looking at the 13C-NMR you notice 10 distinct peaks, and the IR has a characteristic peak around 2250 cm-1. Relative integration is shown. 4 2 2 3 8 7 6 5 4 PPM 3 2 1 0 A) B) NC C) CN D) CN H N E) Ans: D 66 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 64. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C6H10O2? The 13C-NMR shows characteristic chemical shifts at 22.3, 31.1, 117.3, 157.7, and 171.6 ppm. Relative integration is shown. 6 1 exchanges w/ D2O 1 1 1 13 12 11 10 9 8 7 PPM 6 5 4 3 2 1 0 A) B) HO O CO2H C) D) E) Ans: E O O CO2H CO2H 67 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 65. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C11H14O2? Looking at the 13C-NMR you notice a peak at 174 ppm. Relative integration is shown. 3 3 2 2 2 2 8 7 6 5 4 PPM 3 2 1 0 A) O O B) O O C) O O D) O O E) O O Ans: A 68 Topic: Proton NMR- Unknown Identification. Section: 9.2, 9.3 Difficulty Level: Medium 66. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C12H17NO and a characteristic IR stretch near 1700 cm-1 and a characteristic peak in the 13C-NMR at 170 ppm? Relative integration is shown. 3 22 2 3 2 3 8 7 6 5 4 PPM 3 2 1 0 A) O N B) N O C) N HO D) O N E) O N Ans: A 69 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 67. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C9H18O2 and characteristic 13C-NMR peaks at 11.3, 21.6, 25.3, 49.4, 67.1, and 175.5 ppm? Relative integration is shown. 3 2 3 1 1 6 5 4 3 PPM 2 1 0 A) O O B) O O C) O D) O O E) O O Ans: B 70 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 68. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C10H12O2? Relative integration is shown. 3 2 1 2 2 2 11 10 9 8 7 6 PPM 5 4 3 2 1 0 A) O O CHO B) O C) CO2H D) E) CO2H CO2H Ans: C 71 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 69. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C8H16O? Relative integration is shown. 6 3 2 1 2 2 2 PPM 1 0 A) B) O O H C) D) O OH E) O Ans: E 72 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 70. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C6H10O2? Relative integration is shown. 3 2 1 2 2 6 5 4 PPM 3 2 1 0 A) B) O O O O H O C) O D) E) Ans: D O O O OH 73 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 71. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C9H12O? Relative integration is shown. 3 2 2 1 exchanges with D2O 2 2 7 6 5 4 PPM 3 2 1 0 A) B) HO C) HO O D) E) HO OH Ans: E 74 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 72. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C5H8O? The IR spectrum does show a characteristic stretch around 1700 cm-1. Relative integration is shown. 3 3 1 1 8 7 6 5 4 PPM 3 2 1 0 A) B) O O C) D) E) Ans: E O O O 75 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 73. A compound C5H10O gave the following spectral data: 1 H NMR spectrum IR spectrum doublet, δ 1.10 strong peak singlet, δ 2.10 near 1720 cm-1 septet, δ 2.50 Which is a reasonable structure for the compound? O O O I O II O III IV A) B) C) D) E) I II III IV V Ans: E V Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 74. A compound C4H9Br gave the following 1H NMR spectrum: triplet, δ 1.0 (3H); doublet, δ 1.7; multiplet, δ 1.8; multiplet, δ 4.1 (1H) Which is a reasonable structure for the compound? A) CH3CH2CHBrCH3 B) CH3CH2CH2CH2Br C) (CH3)2CHCH2Br D) (CH3)3CBr Ans: A 76 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 75. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C6H12O which shows no characteristic stretches in the IR between 3600-3300 cm-1, but does around 1600 cm-1? Relative integration is shown. 6 3 1 1 1 6 5 4 PPM 3 2 1 0 A) B) C) O O O D) O E) O Ans: A 77 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 76. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C5H11NO, which shows a characteristic stretch in the IR around 1700 cm-1, and a characteristic peak at 202 ppm in the 13C-NMR? Relative integration is shown. 6 2 1 2 10 9 8 7 6 5 PPM 4 3 2 1 0 A) H 2N CHO B) N CHO C) N O D) N H CHO E) N CHO Ans: B 78 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 77. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C8H15ClO3, which shows a characteristic stretch in the IR around 1750 cm-1 but not around 3500 cm-1, and a characteristic peak at 173 ppm in the 13CNMR? Relative integration is shown. 6 4 2 1 2 4 3 PPM 2 1 0 A) O O O Cl O O Cl O B) C) Cl O O O D) Cl O O O E) O Cl O O Ans: C 79 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 78. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C6H12O2? Relative integration is shown. 3 2 2 2 3 10 8 6 PPM 4 2 0 A) B) O O O HO C) D) E) O O O O O Ans: D 80 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 79. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C6H12? Relative integration is shown. 6 3 2 1 8 7 6 5 4 PPM 3 2 1 0 A) B) C) D) E) Ans: B 81 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 80. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C4H7Br? Relative integration is shown. 2 1 1 3 6 5 4 3 PPM 2 1 0 A) Br B) C) Br Br D) E) Ans: C Br Br 82 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 81. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C5H10O? The IR spectrum does not show any characteristic stretches around 1700 cm-1. Relative integration is shown. 2 1 1 3 3 7 6 5 4 PPM 3 2 1 0 A) B) C) O O O D) E) O O Ans: A 83 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 82. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C5H11NO? In the 13C-NMR spectrum you notice that the farthest peak downfield has a chemical shift of 173 ppm. Relative integration is shown. 3 2 1 exchanges with D2O 2 3 9 8 7 6 5 PPM 4 3 2 1 0 A) O N H B) O N H C) O N H D) HN O E) H O N Ans: A 84 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 83. A compound with the molecular formula C10H14 gave the following 1H NMR spectrum: doublet, δ 1.2 singlet, δ 2.3 septet, δ 2.8 multiplet, δ 7.1 A possible structure for the compound is: I II III A) B) C) D) E) I II III IV V Ans: B IV V 85 Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 84. Determine the likely structure for a compound A (C6H10O), which is found to decolorize bromine in carbon tetrachloride. Its spectral data is as follows: 1 H NMR IR -1 triplet, δ 1.0 singlet, δ2.4 2200 cm (sharp) singlet, δ 1.4 singlet, δ3.4 3300 cm-1 (sharp) quartet, δ 1.6 3500 cm-1 (broad) OH OH OH I II III OH OH A) B) C) D) E) I II III IV V Ans: C IV V 86 Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.8B Difficulty Level: Easy 85. In NMR terminology, protons Ha and Hb are said to be: H Cl Hb Ha A) B) C) D) E) Identical Enantiotopic Diastereotopic Homotopic Mesotopic Ans: C Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.8B Difficulty Level: Easy 86. In the structure shown, Ha and Hb are classified as: Hb Ha A) B) C) D) E) homotopic protons. vicinal protons. enantiotopic protons. diastereotopic protons. isomeric protons. Ans: C Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.8B Difficulty Level: Medium 87. In the structure shown, Ha and Hb are classified as: Ha Hb A) B) C) D) E) homotopic protons. vicinal protons. enantiotopic protons. diastereotopic protons. isomeric protons. Ans: D 87 Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.8B Difficulty Level: Medium 88. In the structure shown, Ha and Hb are classified as: HO H Ha H b A) B) C) D) E) homotopic protons. vicinal protons. enantiotopic protons. diastereotopic protons. isomeric protons. Ans: D Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.8B Difficulty Level: Medium 89. In the structure shown, Hb and Hc are classified as: Ha Hb Hc A) B) C) D) E) homotopic protons. geminal protons. enantiotopic protons. diastereotopic protons. isomeric protons. Ans: D 88 Topic: C-13 NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Easy 90. The broadband proton-decoupled 13C NMR spectrum of a hexyl chloride exhibits five signals. Which of these structures could be the correct one for the compound? CH3 A) CH3CCH2CH2Cl CH3 B) Cl CH3CH2CCH2CH3 CH3 CH3 CH3 CH3C CHCH3 C) D) Cl CH3 CH3CHCHCH2CH3 E) Cl CH3 CH3C CHCH3 CH3 Cl Ans: D Topic: C-13 NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Easy 91. How many signals will be recorded in the broadband proton-decoupled 13C spectrum of 4-chloro-1-ethylbenzene? Cl A) B) C) D) E) 2 3 4 6 7 Ans: D 89 Topic: C-13 NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Easy 92. How many 13C signals would 1,4-dimethylbenzene give? A) B) C) D) E) 1 2 3 4 5 Ans: C Topic: C-13 NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Easy 93. How many 13C signals would 1,3-dichlorobenzene give? Cl Cl A) B) C) D) E) 1 2 3 4 5 Ans: D Topic: C-13 NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Easy 94. How many 13C signals would 1,2-dimethylbenzene give? A) B) C) D) E) 1 2 3 4 5 Ans: D 90 Topic: C-13 NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Easy 95. How many 13C signals would you expect from anisole? O A) B) C) D) E) 1 2 3 4 5 Ans: E Topic: Carbon NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Easy 96. For the following compound how many different signals would you see in the carbon NMR? (Assume that you can see them all.) A) B) C) D) E) 3 4 5 6 7 Ans: C 91 Topic: Carbon NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Easy 97. In 13C NMR spectroscopy, the signal due to this type of carbon occurs furthest downfield. A) –C≡N B) C O C) C O D) C X E) –C≡C– Ans: B Topic: C-13 NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Medium 98. The C7 compound which gives 3 signals in the broadband proton-decoupled 13C spectrum could be: A) Heptane B) 2-Methylhexane C) 3,3-Dimethylpentane D) 2,4-Dimethylpentane E) 2,2,3-Trimethylbutane Ans: D 92 Topic: Carbon NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Medium 99. For the following compound how many different signals would you see in the carbon NMR? (Assume that you can see them all.) A) B) C) D) E) 1 2 3 4 5 Ans: E Topic: Carbon NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Medium 100. For the following compound how many different signals would you see in the carbon NMR? (Assume that you can see them all.) A) B) C) D) E) 4 5 6 7 8 Ans: D 93 Topic: Carbon NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Medium 101. For the following compound how many different signals would you see in the carbon NMR? (Assume that you can see them all.) N A) B) C) D) E) 3 4 5 8 9 Ans: A Topic: Carbon NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Medium 102. A bromodichlorobenzene which gives four signals in the broadband proton-decoupled 13 C spectrum could be: Cl Br Cl Br Cl Cl Cl Br Cl Br Cl Cl Br Cl Cl I II III IV A) B) C) D) E) I II III IV V Ans: A V 94 Topic: Carbon NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Hard 103. For the following compound how many different signals would you see in the carbon NMR? (Assume that you can see them all.) S S A) B) C) D) E) 4 5 6 7 8 Ans: C Topic: Carbon NMR and Proton NMR- Symmetry, Chemical Shift Section: 9.2, 9.11 Difficulty Level: Medium 104. Which compound below would give rise to 3 signals in the proton NMR spectrum and 4 signals in the carbon NMR spectrum? (Assume you can separate and see all peaks.) Br I II III IV A) B) C) D) E) I II III IV None of the above. Ans: E 95 Topic: Carbon NMR and Proton NMR- Symmetry, Chemical Shift Section: 9.2, 9.11 Difficulty Level: Hard 105. Which compound below would give rise to 4 signals in the proton NMR spectrum and 4 signals in the carbon NMR spectrum? (Assume you can separate and see all peaks.) Br I A) B) C) D) E) I II III IV More than one of the above. Ans: C II III IV Topic: Carbon NMR and Proton NMR- Symmetry, Chemical Shift Section: 9.2, 9.11 Difficulty Level: Hard 106. Which compound below would give rise to 4 signals in the proton NMR spectrum and 6 signals in the carbon NMR spectrum? (Assume you can separate and see all peaks.) Br I A) B) C) D) E) I II III IV More than one of the above. Ans: A II III IV 96 Topic: Carbon NMR and Proton NMR- Symmetry, Chemical Shift Section: 9.2, 9.11 Difficulty Level: Hard 107. Which compound below would NOT give rise to 4 signals in the proton NMR spectrum and 3 signals in the carbon NMR spectrum? (Assume you can separate and see all peaks.) OH OH OH OH I A) B) C) D) E) II III IV I II III IV All of the above fit the criteria. Ans: C Topic: Carbon NMR and Proton NMR- Symmetry, Chemical Shift Section: 9.2, 9.11 Difficulty Level: Hard 108. Which compound below would give rise to 5 signals in the proton NMR spectrum and 7 signals in the carbon NMR spectrum? (Assume you can separate and see all peaks.) Br I II III IV A) B) C) D) E) I II III IV None of the above. Ans: D 97 Topic: C-13 NMR- Symmetry, Chemical Shift Section: 9.11D Difficulty Level: Easy 109. How will the methyl carbon appear in the proton off-resonance decoupled 13C spectrum of toluene? A) B) C) D) E) Singlet Doublet Triplet Quartet Quintet Ans: D Topic: Mass Spectrometry Section: 9.13 Difficulty Level: Easy 110. A) B) C) D) E) Which is the base peak? 15 29 44 45 100 Ans: B 98 Topic: Mass Spectrometry Section: 9.13 Difficulty Level: Easy 111. A) B) C) D) E) Which is the likely molecular ion (M+•)? 15 29 44 45 100 Ans: C Topic: Mass Spectrometry Section: 9.16 Difficulty Level: Easy 112. A) B) C) D) E) A prominent (M+• -18) peak suggests that the compound might be a(n): Alkane Alcohol Ether Ketone Primary amine Ans: B Topic: Mass Spectrometry Section: 9.16 Difficulty Level: Medium Predict the base peak for 2-chloro-2-methylpropane 113. A) B) C) D) E) m/z 15 m/z 92 m/z 43 m/z 57 m/z 77 Ans: D 99 Topic: Mass Spectrometry Section: 9.16 Difficulty Level: Medium 114. A) B) C) D) E) Select the structure of a compound C6H14 with a base peak at m/z 43. CH3CH2CH2CH2CH2CH3 (CH3CH2)2CHCH3 (CH3)3CCH2CH3 (CH3)2CHCH(CH3)2 None of these Ans: D Topic: Mass Spectrometry Section: 9.17 Difficulty Level: Medium 115. What is the molecular formula of this compound? m/z 84 M+• 85 86 C5H10O C5H8O C5H24 C6H12 C4H6O2 Ans: B intensity 10.00 0.56 0.04 A) B) C) D) E) Topic: Mass Spectrometry Section: 9.17 Difficulty Level: Medium 116. What is the molecular formula of this compound? m/z 78 M+• 79 80 81 C6H6 C3H5Cl C6H8 C6H9 C3H7Cl Ans: E intensity 10.00 1 3.3 0.3 A) B) C) D) E) 100 Topic: Mass Spectrometry Section: 9.17A Difficulty Level: Easy 117. The mass spectra of alkyl bromides and chlorides are characterized by an unusually intense __________. A) base peak B) parent peak C) M+• +1 peak D) M+• +2 peak E) None of these Ans: D Topic: Mass Spectrometry Section: 9.17A Difficulty Level: Hard 118. The data below from the molecular ion region of the mass spectrum of a halogencontaining compound are consistent with the presence of what halogen(s) in the original compound? intensity 51.0 M+• + 100.0 M • +2 + 49.0 M • +4 One Br One Cl One Br and one Cl Two Br Two Cl Ans: D A) B) C) D) E) SHORT ANSWER QUESTIONS Topic: General Section: 9.1 Difficulty Level: Easy 119. “NMR” stands for _______________________. Ans: nuclear magnetic resonance 101 Topic: Structure Elucidation Section: 9.2 Difficulty Level: Medium 120. Briefly explain how you might distinguish between the following substances by comparing their 1H-NMR spectra: O O O O I II Ans: The main difference would likely be in the chemical shift of the methine proton of the isopropyl group. The methine proton in I is likely to be more deshielded, and produce a signal (septet) at about 3.5 ppm, while the analogous proton in II is likely to be found, also as a septet, at about 2.3 ppm. O O O O I ~3.5 ppm II ~2.3 ppm 102 Topic: Structure Elucidation Section: 9.2 Difficulty Level: Medium 121. Briefly explain how you might distinguish between the following substances by comparing their 1H-NMR spectra: O O O O I II Ans: The main difference would likely be in the chemical shifts of the methine proton of the isopropyl group and the methylene proton closest to the ester function. The methine proton in I is likely to be more deshielded, and produce a signal (septet) at about 3.5 ppm, while the analogous proton in II is likely to be found, also as a septet, at about 2.3 ppm. By contrast, the methylene proton in II is likely to be more deshielded, and produce a signal (triplet) at about 3.4 ppm, while the analogous proton in II is likely to be found, also as a triplet, at about 2.2 ppm. I O O O O II ~3.5 ppm (septet) ~2.2 ppm (triplet) ~2.3 ppm (septet) ~3.4 ppm (triplet) 103 Topic: Structure Elucidation Section: 9.2 Difficulty Level: Medium 122. Briefly explain how you might distinguish between the following substances by comparing their 1H-NMR spectra: O N H H N O I II Ans: The main difference would likely be in the chemical shifts of the methine proton of the isopropyl group and the methylene proton closest to the amide function. The methine proton in I is likely to be more deshielded, and produce a signal (septet) at about 3.5 ppm, while the analogous proton in II is likely to be found, also as a septet, at about 2.3 ppm. By contrast, the methylene proton in II is likely to be more deshielded, and produce a signal (triplet) at about 3.4 ppm, while the analogous proton in II is likely to be found, also as a triplet, at about 2.2 ppm. I II O N H H N O ~3.2 ppm (septet) ~2.2 ppm (triplet) Topic: 1H NMR Section: 9.2 Difficulty Level: Medium ~2.3 ppm (septet) ~3.1 ppm (triplet) 123. Predict the 1H NMR spectrum of diethoxymethane, CH3CH2OCH2OCH2CH3. Ans: ~1.2 ppm triplet > O O ~1.2 ppm triplet > ~3.4 ppm quartet > > > ~4.9 ppm singlet ~3.4 ppm quartet 104 Topic: 1H NMR Section 9.2 Difficulty Level: Medium 124. Predict the 1H NMR spectrum of 2-chloroethanal, CH2ClCHO. Ans: 9-10 ppm triplet > Cl O 4-5 ppm doublet Topic: 1H NMR Section: 9.2A Difficulty Level: Easy 125. Predict the number of signals in the 1H NMR spectrum of 2-methyl-2-pentanol. Ans: Five 1 1' 2 3 4 Topic: General, Chemical Shift Section: 9.2A Difficulty Level: Medium 126. A shielded proton will absorb at a higher frequency (this is the ________ end of the spectrum); and a deshielded proton will absorb at a lower frequency (the _____________ end of the spectrum). Ans: upfield; downfield > OH 5 105 Topic: General, Signal Integration Section: 9.2B Difficulty Level: Easy 127. When measuring the integral for a particular peak in the NMR spectrum, we are not interested in the peak height as much as in the ____________________. Ans: area under the peak Topic: Structure Elucidation Section: 9.2, 9.3 Difficulty Level: Easy 128. Examine the 1H NMR spectrum of 1-nitropropane, shown below. Assign the signals to the respective hydrogen atoms in the molecule. Ans: 4.3 ppm triplet > NO2 1.0 ppm triplet > 2.0 ppm sextet > 106 Topic: Structure Elucidation Section: 2.16, 9.2, 9.3 Difficulty Level: Medium 129 An unknown compound, A, has the formula C7H14O. Elucidate the structure of A by . scrutinizing its IR, 1H NMR and 13C NMR spectra, shown below. Ans: O 4-Heptanone 107 Topic: General Section: 9.4 Difficulty Level: Easy 130. Which form of electromagnetic radiation possesses the least energy? Ans: radiofrequency radiation Topic: Reference Compound Section: 9.7 Difficulty Level: Easy 131. What compound is used as the standard “zero” reference in both carbon and proton NMR? Ans: TMS or tetramethylsilane or (CH3)4 Si Topic: General, Bond Rotation, Proton Exchange Section: 9.10 Difficulty Level: Medium 132. Name two rapid processes that occur in organic molecules. Ans: Rotation about C-C single bonds; chemical exchange of protons attached to electronegative atoms 108 Topic: 13C NMR, Structure Elucidation Section: 9.11 Difficulty Level: Medium 133. Interpret the following 13C/DEPT spectrum of a compound C5H10Br2: elucidate the structure and assign all the 13C resonances. Ans: Br 32 ppm > > > > Br 33 ppm > 27 ppm 33 ppm 109 Topic: Structure Elucidation Section: 2.16, 9.2, 9.3, 9.11 Difficulty Level: Medium 134. An unknown compound, C, has the formula C7H7Br. Elucidate the structure of C by scrutinizing its IR, 1H NMR and 13C NMR spectra, shown below. 110 Ans: Br 4-Bromotoluene 111 Topic: Structure Elucidation Section: 2.16, 9.2, 9.3. 9.11 Difficulty Level: Medium 135. An unknown compound, F, has the formula C3H6O2. Elucidate the structure of F by scrutinizing its IR, 1H NMR and 13C NMR spectra, shown below. 112 Ans: O OH Propanoic acid 113 Topic: Structure Elucidation Section: 2.16, 9.2, 9.3, 9.11 Difficulty Level: Medium 136. An unknown compound, L, has the formula C5H10O2. Elucidate the structure of L by scrutinizing its IR, 1H NMR and 13C NMR spectra, shown below. Ans: O O Methyl butyrate 114 Topic: Structure Elucidation Section: 2.16, 9.2, 9.3, 9.11 Difficulty Level: Hard 137. An unknown compound, I, has the formula C3H7NO2. Elucidate the structure of I by scrutinizing its IR, 1H NMR and 13C NMR spectra, shown below. Ans: NO2 1-Nitropropane 115 Topic: Structure Elucidation Section: 2.16, 9.2, 9.3, 9.11 Difficulty Level: Hard 138. An unknown compound, E, has the formula C6H12O. Elucidate the structure of E by scrutinizing its IR, 1H NMR and 13C NMR spectra, shown below. Ans: O 2-Hexanone 116 Topic: Structure Elucidation Section: 2.16, 9.2, 9.3, 9.11 Difficulty Level: Hard 139. An unknown compound, U, has the formula C6H4Cl2O. Elucidate the structure of U by scrutinizing its IR, 1H NMR and 13C NMR spectra, shown below. 117 Ans: OH Cl Cl 2,6-dichlorophenol 118 Topic: Structure Elucidation Section: 2.16, 9.2, 9.3, 9.11 Difficulty Level: Hard 140. An unknown compound, V, has the formula C8H10O. Elucidate the structure of V by scrutinizing its IR, 1H NMR and 13C NMR spectra, shown below. 119 Ans: OH 2,6-dimethylphenol 120 Topic: Base Peak Section: 9.13 Difficulty Level: Easy 141. In mass spectrometry, the most intense peak is assigned an intensity of 100%, and is referred to as the ______________. Ans: base peak Topic: m/z Ratio Section: 9.13 Difficulty Level: Easy 142. A mass spectrometer sorts ions on the basis of their _______________. Ans: mass to charge ratio Topic: Molecular Ion Section: 9.14 Difficulty Level: Easy 143. In electron impact mass spectrometry, a beam of high-energy electrons initially dislodges one electron from the compound being studied. This produces a positively charged ion called the ____________________. Ans: molecular ion Topic: Relative Abundance Section: 9.17 Difficulty Level: Easy 144. What can be determined from the relative abundance of the M+• +1 peak? Ans: An approximation for the number of carbon atoms in the molecule. Topic: Relative Abundance Section: 9.17 Difficulty Level: Easy 145. What can be determined from the relative abundance of the M+• +2 peak? Ans: The presence of a number of different elements, including S, Br, and Cl. Topic: Nitrogen Rule Section: 9.17B Difficulty Level: Medium 146. What is the nitrogen rule? Ans: If the molecular ion peak is even, the molecule must contain an even number of nitrogen atoms (zero is an even number). If the molecular ion peak is odd, the molecule must contain an odd number of nitrogen atoms.) 121