1121792871 organic chemistry 1
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Chapter Nine
MULTIPLE CHOICE QUESTIONS
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2Difficulty Level: Easy
1. How many signals would you expect to find in the 1H NMR spectrum of CH3OCH2CH2OCH3?
A) 1B) 2C) 3D) 4E) 5
Ans: B
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2Difficulty Level: Easy
2. Predict the splitting pattern you would observe for the proton at C1 of 2,3-dimethyl-2-phenylbutane.
A) DoubletB) SingletC) QuartetD) SeptetE) Octet
Ans: B
545
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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?
OCH3
A) 1.10 ppm, singletB) 2.10 ppm, doubletC) 3.40 ppm, singletD) 4.5 ppm, singletE) 3.5 ppm, quartet
Ans: C
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 1.00 ppm, singletB) 2.10 ppm, singletC) 2.10 ppm, quartetD) 3.00 ppm, singletE) 2.10 ppm, triplet
Ans: B
546
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 1.00 ppm, quartetB) 2.40 ppm, singletC) 2.40 ppm, quartetD) 3.00 ppm, quartetE) 2.40 ppm, triplet
Ans: C
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 1.00 ppm, quartetB) 2.40 ppm, singletC) 2.40 ppm, quartetD) 3.00 ppm, quartetE) 1.00 ppm, triplet
Ans: E
547
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 5.40 ppm, multipletB) 2.00 ppm, multipletC) 2.00 ppm, doubletD) 2.00 ppm, quartetE) 5.40 ppm, doublet
Ans: A
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 5.40 ppm, doubletB) 1.00 ppm, multipletC) 2.00 ppm, doubletD) 1.00 ppm, doubletE) 5.40 ppm, multiplet
Ans: D
548
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 3.00 ppm, doubletB) 3.00 ppm, tripletC) 5.00 ppm, tripletD) 1.00 ppm, doubletE) 5.40 ppm, multiplet
Ans: B
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 3.00 ppm, doubletB) 3.00 ppm, tripletC) 5.00 ppm, tripletD) 1.00 ppm, doubletE) 3.00 ppm, singlet
Ans: E
549
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 4B) 5C) 6D) 7E) 8
Ans: A
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 4B) 5C) 6D) 7E) 8
Ans: C
550
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 1B) 2C) 3D) 4E) 5
Ans: C
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty Level: Easy
14. A downfield ( 9-10) singlet is observed in the 1H NMR spectrum of:A)
CH3CCH2CH3
O
B)
C6H5CH2C O
H
C)
(CH3)2CHC O
H
D)
(CH3)3CC O
H
E)
C6H5CH2CCH3
O
Ans: D
551
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 1B) 2C) 3D) 4E) 5
Ans: D
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 4B) 5C) 6D) 7E) 8
Ans: B
552
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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?
OCH3
A) 1.10 ppm, singletB) 2.10 ppm, tripletC) 3.40 ppm, tripletD) 4.5 ppm, singletE) 5.3 ppm, doublet
Ans: D
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2Difficulty Level: Medium
18. Predict the splitting pattern you would observe for the proton at C4 of 2,3-dimethyl-2-phenylbutane.
A) DoubletB) SingletC) QuartetD) SeptetE) Octet
Ans: A
553
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2Difficulty Level: Medium
19. How many 1H NMR signals would trans-1,2-dichlorocyclopropane give?A) 1B) 2C) 3D) 4E) 5
Ans: B
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2Difficulty Level: Medium
20. How many chemically distinct 1H NMR signals are there in the following compound?
A) 1B) 2C) 3D) 4E) 5
Ans: D
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2Difficulty Level: Medium
21. How many 1H NMR signals would cis-1,2-dichlorocyclopropane give?A) 1B) 2C) 3D) 4E) 5
Ans: C
554
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2Difficulty Level: Medium
22. How many 1H NMR signals would you expect from this compound?
A) 1B) 2C) 3D) 4E) 5
Ans: B
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2Difficulty 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-methylpentaneB) 3-chloro-2-methylpentaneC) 3-chloropentaneD) 1-chloro-2,2-dimethylbutaneE) 3-chloro-3-methylpentane
Ans: E
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty Level: Medium
555
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) 1.00 ppm, doubletB) 2.00 ppm, singletC) 2.00 ppm, tripletD) 2.00 ppm, doubletE) 1.00 ppm, triplet
Ans: D
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty Level: Medium
25. A compound C5H11Cl which exhibits only two singlets in the 1H NMR spectrum must be:
A) 1-ChloropentaneB) 1-Chloro-2,2-dimethylpropaneC) 1-Chloro-2-methylbutaneD) 3-ChloropentaneE) 1-Chloro-3-methylbutane
Ans: B
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 7 signals: all singletsB) 7 signals: 4 singlets, 3 doubletsC) 3 signals: all singletsD) 3 signals: one singlet, 2 doubletsE) 3 signals: two singlets, one doublet
Ans: C
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty Level: Medium
556
27. Consider the expected 1H NMR spectrum of 2,4-dimethyl-1,4-pentadiene. Which of the following is likely to be observed?
A) 7 signals: all singletsB) 4 signals: all singletsC) 3 signals: all singletsD) 3 signals: one singlet, 2 doubletsE) 4 signals: two singlets, two doublets
Ans: E
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2Difficulty 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) 2B) 5C) 6D) 8E) 12
Ans: E
Topic: Structure Elucidation Section: 2.16, 9.2Difficulty Level: Medium
557
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?
A) IB) IIC) IIID) IVE) V
Ans: A
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2ADifficulty 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?
A) Protons on carbon IB) Protons on carbon IIC) Protons on carbon IIID) Protons on carbon IVE) Protons on carbon V
Ans: A
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2ADifficulty Level: Hard
558
31. The 1H NMR signal for which of the indicated protons occurs farthest downfield?
A) IB) IIC) IIID) IVE) V
Ans: E
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2CDifficulty Level: Easy
32. Which proton(s) of the compound below would appear as a septet in the 1H NMR spectrum?
A) The protons on carbon IB) The protons on carbon IIC) The protons on carbon IIID) The protons on carbon IVE) The protons on carbon V
Ans: B
559
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2CDifficulty Level: Easy
33. Which proton(s) of the compound below would appear as a doublet in the 1H NMR spectrum?
A) The protons on carbon IB) The protons on carbon IIC) The protons on carbon IIID) The protons on carbon IVE) The protons on carbon V
Ans: A
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2CDifficulty Level: Easy
34. Which proton(s) of the compound below would appear as a triplet in the 1H NMR spectrum?
A) The protons on carbon IIB) The protons on carbon I and VC) The protons on carbon III and VD) The protons on carbon III and IVE) The protons on carbon V
Ans: C
560
Topic: Proton NMR- Symmetry, Splitting, Chemical shiftSection: 9.2CDifficulty Level: Easy
35. Consider the expected splitting of signal “b” in the 1H NMR spectrum of 1-methoxy-2-methylpropane, 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) 8B) 9C) 12D) 21E) 24
Ans: D
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2CDifficulty Level: Medium
36. Predict the splitting pattern you would observe for the proton at C3 of 2,3-dimethyl-2-phenylbutane.
A) DoubletB) SingletC) QuartetD) SeptetE) Octet
Ans: D
Topic: Proton NMR- Symmetry, Splitting, Chemical Shift
561
Section: 9.2CDifficulty Level: Medium
37. Which of these compounds will not be represented by a singlet only in the 1H NMR spectrum?
A) NeopentaneB) HexamethylbenzeneC) IsobutaneD) (Z)-1,2-DichloroetheneE) (E)-1,2-Dichloroethene
Ans: C
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2CDifficulty Level: Hard
38. Consider the expected splitting of the C2 proton signal in the 1H NMR spectrum of 1,1-dibromopentane. 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) 3B) 4C) 5D) 6E) 8
Ans: D
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2CDifficulty Level: Hard
562
39. Consider the expected splitting of signal “b” in the 1H NMR spectrum of N-methyl-1-propanamine, 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) 2B) 5C) 6D) 8E) 12
Ans: E
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2CDifficulty Level: Hard
40. Consider the expected splitting of signal “b” in the 1H NMR spectrum of 1,1-dichloro-3-methylbutane, 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) 8B) 9C) 12D) 18E) 21
Ans: E
Topic: Proton NMR- Symmetry, Splitting, Chemical shiftSection: 9.2CDifficulty Level: Hard
563
41. Consider the expected splitting of signal “b” in the 1H NMR spectrum of 1,2-dimethoxypropane, 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”?
A) 2B) 5C) 6D) 8E) 12
Ans: E
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2CDifficulty Level: Hard
42. Consider the expected splitting of signal “c” in the 1H NMR spectrum of 2-ethyl-1-butanol, 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) 6B) 7C) 8D) 12E) 15
Ans: E
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2CDifficulty Level: Hard
564
43. Consider the expected splitting of the C2 proton signal in the 1H NMR spectrum of 2-ethyl-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) 6B) 7C) 8D) 12E) 15
Ans: E
Topic: Proton NMR- Symmetry, Splitting, Chemical ShiftSection: 9.2CDifficulty 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?
A) 1B) 6C) 7D) 8E) 9
Ans: C
565
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2CDifficulty 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) ?
A) 3, 6, 4, 1B) 3, 6, 4, 3C) 3, 12, 3, 1D) 3, 12, 3, 3E) 3, 12, 6, 3
Ans: E
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2, 9.2CDifficulty Level: Medium
46. The 1H NMR spectrum of which of the compounds below, all of formula C7H12O2, would consist of two singlets only?
A) I
B) IIC) IIID) IVE) V
Ans: E
566
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2, 9.2CDifficulty Level: Hard
47. The 1H NMR spectrum of which of the compounds below, all of formula C7H12O2, would consist of three singlets only?
A) I
B) IIC) IIID) IVE) V
Ans: B
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.2, 9.2CDifficulty 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?
A) I
B) IIC) IIID) IVE) V
Ans: D
567
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.2A, 9.2CDifficulty Level: Medium
49. A compound with the molecular formula C4H10O gives a 1H NMR spectrum consisting only of a quartet centered at 3.5 and a triplet at 1.1. The most likely structure for the compound is:
A)
CH3COH
CH3
CH3B)
CH3OCHOH
CH3
C) CH3CH2CH2CH2OHD) CH3CH2OCH2CH3E) CH3CHCH2OH
CH3Ans: D
568
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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 13C-NMR chemical shifts (ppm): 108.4, 50.9, 31.6, 23.5, 2.0. Relative integration is known.
0123PPM
6
2
3 3
A) OO
B) O
OC)
O
O
D)
O
O
E)
O OAns: C
569
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
024681012PPM
1
5
2
2
A) CHO
B) CO2H
C) CO2H
D)
HO2C
E) CO2H
Ans: C
570
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
012345678PPM
2
9
3
A)
B)
C) C
D)
E)
Ans: D
571
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
012345678PPM
1
4
6
A) CNB)
C) CN
D) CN
E)
NH
Ans: D
572
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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 1.25 a septet at 2.90 and a multiplet at 7.25
I II III IV V]
A) IB) IIC) IIID) IVE) V
Ans: D
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty Level: Medium
55. A compound with the molecular formula C10H13Cl gave the following 1H NMR spectrum: singlet, 1.6 singlet, 3.1 multiplet, 7.2 (5H)The most likely structure for the compound is:
A) IB) IIC) IIID) IVE) V
Ans: B
573
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty Level: Medium
56. A compound with the molecular formula C8H9BrO gave the following 1H NMR spectrum: triplet, 1.4 quartet, 3.9 multiplet, 7.0 (4H)There was no evidence of an -OH band in the IR spectrum. A possible structure for the compound is:
A) IB) IIC) IIID) IVE) V
Ans: C
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty Level: Medium
574
57. A compound with the molecular formula C6H15N gave the following 1H NMR spectrum: triplet, 0.90 quartet, 2.4There were no other signals. The most likely structure for the compound is:
A) CH3NCH2CH3
CH2CH2CH3B) CH3NCH2CH2CH2CH3
CH3C) CH3CH2CH2CH2CH2CH2NH2D) CH3CH2NCH2CH3
CH2CH3E) CH3CH2CH2NCH2CH2CH3
HAns: D
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty Level: Medium
58. A compound with the molecular formula C8H9ClO gave the following 1H NMR spectrum: triplet, 3.7 triplet, 4.2 multiplet, 7.1There was no evidence of an -OH band in the IR spectrum. The most likely structure for the compound is:
A) IB) IIC) IIID) IVE) V
Ans: A
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3
575
Difficulty Level: Medium
59. A compound with the molecular formula C3H6Cl2 gave a 1H NMR spectrum consisting only of a triplet centered at 3.7 and a quintet centered at 2.2. The most likely structure for the compound is:
A) CH3CH2CHCl2
B) CH3CHClCH2ClC) ClCH2CHClCH3
D) ClCH2CH2CH2ClE) CH3CCl2CH3
Ans: D
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty Level: Medium
576
60. What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C10H20? Relative integration is shown.
012345678PPM
23
A)
B)
C)
D)
E)
Ans: C
577
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
012345678PPM
1 1
A)
OB)
OHC) OH
D) O
E) O
Ans: D
578
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
012345PPM
2
1
3
A) O O
O OB)
OO
H H
C)OO
O OD) O
O
O
O
E)
O
O
O
OAns: A
579
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
012345678PPM
4
2 23
A)
B)
NCC)
CN
D)
CNE) H
N
Ans: D
580
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
012345678910111213PPM
exchanges w/ D2O
1
1 1 1
6
A)HO
O
B) CO2H
C) O
OD) CO2H
E) CO2H
Ans: E
581
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
012345678PPM
2 2 2
3
23
A)
O
O
B) OO
C) O
OD)
O
OE)
O
OAns: A
582
Topic: Proton NMR- Unknown Identification.Section: 9.2, 9.3Difficulty Level: Medium
583
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.
012345678PPM
22
3
2
3
2
3
A) O
N
B)N
OC)
HO
N
D) O
N
E) O
N
Ans: A
584
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
0123456PPM
1 1
2
3 3
A)O
O
B)
O
O
C)
O
D)
O
O
E)
OO
Ans: B
585
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
01234567891011PPM
1
2 2 2 23
A) CHO
O
B) O
O
C) CO2H
D) CO2H
E) CO2H
Ans: C
586
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
012PPM
1
2 2 2
6
3
A) O
B)
H
O
C) OH
D)
OE) O
Ans: E
587
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
0123456PPM
1
2 2 2
3
A)
O
O
B)O
H
O
C)
O
O
D)
O
O
E) O
OHAns: D
588
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
01234567PPM
exchanges with D2O
2 2
1
2 2
3
A) O
B) HO
C)
HO
D) OH
E)
HOAns: E
589
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
012345678PPM
1 1
33
A)O
B) O
C)O
D) O
E) O
Ans: E
590
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty Level: Medium
73. A compound C5H10O gave the following spectral data:1 H NMR spectrum IR spectrumdoublet, 1.10 strong peaksinglet, 2.10 near 1720 cm-1
septet, 2.50Which is a reasonable structure for the compound?
A) IB) IIC) IIID) IVE) V
Ans: E
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty Level: Medium
74. A compound C4H9Br gave the following 1H NMR spectrum:triplet, 1.0 (3H); doublet, 1.7; multiplet, 1.8; multiplet, 4.1 (1H)Which is a reasonable structure for the compound?
A) CH3CH2CHBrCH3
B) CH3CH2CH2CH2BrC) (CH3)2CHCH2BrD) (CH3)3CBr
Ans: A
591
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
0123456PPM
1 1 1
3
6
A) O
B) O
C)
OD) O
E) O
Ans: A
592
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
012345678910PPM
1
2
6
2
A)H2N
CHO
B)N
CHOC)
N
OD)
NH
CHO
E)
N CHO
Ans: B
593
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty Level: Hard
594
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 13C-NMR? Relative integration is shown.
01234PPM
1
4
2 2
6
A)
Cl
O
O
O
B)
O
O
Cl
O
C)
Cl
O
O
O
D) O
OCl
O
E)
O
O
O
ClAns: C
595
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
0246810PPM
2 2 2
3 3
A) O
OB)
HO
O
C) O
D) O
OE)
O
O
Ans: D
Topic: Proton NMR- Unknown Identification
596
Section: 9.2, 9.3Difficulty 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.
012345678PPM
21
3
6
A)
B)
C)
D)
E)Ans: B
597
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
0123456PPM
1 12
3
A) BrB) Br
C)
BrD) Br
E) Br
Ans: C
598
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
01234567PPM
1 12
3 3
A) O
B) O
C)
O
D) O
E) OAns: A
599
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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.
0123456789PPM
exchanges with D2O
1
3 32 2
A)
NH
O
B)
NH
O
C)
NH
O
D)
O
HN
E)
H N
O
Ans: A
600
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty Level: Hard
83. A compound with the molecular formula C10H14 gave the following 1H NMR spectrum: doublet, 1.2 singlet, 2.3 septet, 2.8 multiplet, 7.1A possible structure for the compound is:
A) IB) IIC) IIID) IVE) V
Ans: B
601
Topic: Proton NMR- Unknown IdentificationSection: 9.2, 9.3Difficulty 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 triplet, 1.0 singlet, 2.4 2200 cm-1 (sharp) singlet, 1.4 singlet, 3.4 3300 cm-1 (sharp) quartet, 1.6 3500 cm-1 (broad)
A) IB) IIC) IIID) IVE) V
Ans: C
602
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.8BDifficulty Level: Easy
85. In NMR terminology, protons Ha and Hb are said to be:
A) IdenticalB) EnantiotopicC) DiastereotopicD) HomotopicE) Mesotopic
Ans: C
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.8BDifficulty Level: Easy
86. In the structure shown, Ha and Hb are classified as:
A) homotopic protons.B) vicinal protons.C) enantiotopic protons.D) diastereotopic protons.E) isomeric protons.
Ans: C
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.8BDifficulty Level: Medium
87. In the structure shown, Ha and Hb are classified as:
A) homotopic protons.B) vicinal protons.C) enantiotopic protons.D) diastereotopic protons.E) isomeric protons.
Ans: D
603
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.8BDifficulty Level: Medium
88. In the structure shown, Ha and Hb are classified as:
A) homotopic protons.B) vicinal protons.C) enantiotopic protons.D) diastereotopic protons.E) isomeric protons.
Ans: D
Topic: Proton NMR- Chemical Shift, Splitting, Etc.Section: 9.8BDifficulty Level: Medium
89. In the structure shown, Hb and Hc are classified as:
A) homotopic protons.B) geminal protons.C) enantiotopic protons.D) diastereotopic protons.E) isomeric protons.
Ans: D
604
Topic: C-13 NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty 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?
A)
CH3CCH2CH2Cl
CH3
CH3B)
CH3CH2CCH2CH3
Cl
CH3C)
CH3C CHCH3
CH3
Cl
CH3
D)
CH3CHCHCH2CH3
CH3
ClE)
CH3C CHCH3
CH3
CH3 Cl
Ans: D
Topic: C-13 NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty Level: Easy
91. How many signals will be recorded in the broadband proton-decoupled 13C spectrum of 4-chloro-1-ethylbenzene?
A) 2B) 3C) 4D) 6E) 7
Ans: D
605
Topic: C-13 NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty Level: Easy
92. How many 13C signals would 1,4-dimethylbenzene give?
A) 1B) 2C) 3D) 4E) 5
Ans: C
Topic: C-13 NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty Level: Easy
93. How many 13C signals would 1,3-dichlorobenzene give?
A) 1B) 2C) 3D) 4E) 5
Ans: D
Topic: C-13 NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty Level: Easy
94. How many 13C signals would 1,2-dimethylbenzene give?
A) 1B) 2C) 3D) 4E) 5
Ans: D
606
Topic: C-13 NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty Level: Easy
95. How many 13C signals would you expect from anisole?
A) 1B) 2C) 3D) 4E) 5
Ans: E
Topic: Carbon NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty 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) 3B) 4C) 5D) 6E) 7
Ans: C
607
Topic: Carbon NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty Level: Easy
97. In 13C NMR spectroscopy, the signal due to this type of carbon occurs furthest downfield.
A) –CNB)
C O
C)C O
D)C X
E) –CC–Ans: B
Topic: C-13 NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty Level: Medium
98. The C7 compound which gives 3 signals in the broadband proton-decoupled 13C spectrum could be:
A) HeptaneB) 2-MethylhexaneC) 3,3-DimethylpentaneD) 2,4-DimethylpentaneE) 2,2,3-Trimethylbutane
Ans: D
608
Topic: Carbon NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty 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) 1B) 2C) 3D) 4E) 5
Ans: E
Topic: Carbon NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty 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) 4B) 5C) 6D) 7E) 8
Ans: D
609
Topic: Carbon NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty 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) 3B) 4C) 5D) 8E) 9
Ans: A
Topic: Carbon NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty Level: Medium
102. A bromodichlorobenzene which gives four signals in the broadband proton-decoupled 13C spectrum could be:
A) IB) IIC) IIID) IVE) V
Ans: A
610
Topic: Carbon NMR- Symmetry, Chemical ShiftSection: 9.11Difficulty 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) 4B) 5C) 6D) 7E) 8
Ans: C
Topic: Carbon NMR and Proton NMR- Symmetry, Chemical ShiftSection: 9.2, 9.11Difficulty 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.)
I II III IV
Br
A) IB) IIC) IIID) IVE) None of the above.
Ans: E
611
Topic: Carbon NMR and Proton NMR- Symmetry, Chemical ShiftSection: 9.2, 9.11Difficulty 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.)
I II III IV
Br
A) IB) IIC) IIID) IVE) More than one of the above.
Ans: C
Topic: Carbon NMR and Proton NMR- Symmetry, Chemical ShiftSection: 9.2, 9.11Difficulty 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.)
I II III IV
Br
A) IB) IIC) IIID) IVE) More than one of the above.
Ans: A
612
Topic: Carbon NMR and Proton NMR- Symmetry, Chemical ShiftSection: 9.2, 9.11Difficulty 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 II III IV
A) IB) IIC) IIID) IVE) All of the above fit the criteria.
Ans: C
Topic: Carbon NMR and Proton NMR- Symmetry, Chemical ShiftSection: 9.2, 9.11Difficulty 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.)
I II III IV
Br
A) IB) IIC) IIID) IVE) None of the above.
Ans: D
613
Topic: C-13 NMR- Symmetry, Chemical ShiftSection: 9.11DDifficulty Level: Easy
109. How will the methyl carbon appear in the proton off-resonance decoupled 13C spectrum of toluene?
A) SingletB) DoubletC) TripletD) QuartetE) Quintet
Ans: D
Topic: Mass SpectrometrySection: 9.13Difficulty Level: Easy
110. Which is the base peak?A) 15B) 29C) 44D) 45E) 100
Ans: B
614
Topic: Mass SpectrometrySection: 9.13Difficulty Level: Easy
111. Which is the likely molecular ion (M)?
A) 15B) 29C) 44D) 45E) 100
Ans: C
Topic: Mass SpectrometrySection: 9.16Difficulty Level: Easy
112. A prominent (M-18) peak suggests that the compound might be a(n):
A) AlkaneB) AlcoholC) EtherD) KetoneE) Primary amine
Ans: B
Topic: Mass SpectrometrySection: 9.16Difficulty Level: Medium
113. Predict the base peak for 2-chloro-2-methylpropaneA) m/z 15B) m/z 92C) m/z 43D) m/z 57E) m/z 77
Ans: D
615
Topic: Mass SpectrometrySection: 9.16Difficulty Level: Medium
114. Select the structure of a compound C6H14 with a base peak at m/z 43.A) CH3CH2CH2CH2CH2CH3
B) (CH3CH2)2CHCH3
C) (CH3)3CCH2CH3
D) (CH3)2CHCH(CH3)2
E) None of theseAns: D
Topic: Mass SpectrometrySection: 9.17Difficulty Level: Medium
115. What is the molecular formula of this compound?
m/z intensity 84 M
10.00 85 0.56 86 0.04
A) C5H10OB) C5H8OC) C5H24
D) C6H12
E) C4H6O2
Ans: B
Topic: Mass SpectrometrySection: 9.17Difficulty Level: Medium
116. What is the molecular formula of this compound?
m/z intensity 78 M
10.00 79 1 80 3.3 81 0.3
A) C6H6
B) C3H5ClC) C6H8
D) C6H9
E) C3H7ClAns: E
616
Topic: Mass SpectrometrySection: 9.17ADifficulty Level: Easy
117. The mass spectra of alkyl bromides and chlorides are characterized by an unusually intense __________.
A) base peakB) parent peakC) M
peakD) M
+2 peakE) None of these
Ans: D
Topic: Mass SpectrometrySection: 9.17ADifficulty Level: Hard
118. The data below from the molecular ion region of the mass spectrum of a halogen-containing compound are consistent with the presence of what halogen(s) in the original compound?
intensity
M 51.0
M+2 100.0
M+4 49.0
A) One BrB) One ClC) One Br and one ClD) Two BrE) Two Cl
Ans: D
SHORT ANSWER QUESTIONS
Topic: GeneralSection: 9.1Difficulty Level: Easy
119. “NMR” stands for _______________________.Ans: nuclear magnetic resonance
617
Topic: Structure Elucidation Section: 9.2Difficulty Level: Medium
120. Briefly explain how you might distinguish between the following substances by comparing their 1H-NMR spectra:
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.
618
Topic: Structure Elucidation Section: 9.2Difficulty Level: Medium
121. Briefly explain how you might distinguish between the following substances by comparing their 1H-NMR spectra:
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.
619
Topic: Structure Elucidation Section: 9.2Difficulty Level: Medium
122. Briefly explain how you might distinguish between the following substances by comparing their 1H-NMR spectra:
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.
Topic: 1H NMRSection: 9.2Difficulty Level: Medium
123. Predict the 1H NMR spectrum of diethoxymethane, CH3CH2OCH2OCH2CH3.
Ans:
O O
>
~4.9 ppmsinglet
>
~3.4 ppmquartet
>
~3.4 ppmquartet
>
~1.2 ppmtriplet
>
~1.2 ppmtriplet
620
Topic: 1H NMRSection 9.2Difficulty Level: Medium
124. Predict the 1H NMR spectrum of 2-chloroethanal, CH2ClCHO.
Ans:
ClO>
4-5 ppmdoublet
>
9-10 ppmtriplet
Topic: 1H NMRSection: 9.2ADifficulty Level: Easy
125. Predict the number of signals in the 1H NMR spectrum of 2-methyl-2-pentanol.
Ans: Five
Topic: General, Chemical ShiftSection: 9.2ADifficulty 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
621
Topic: General, Signal IntegrationSection: 9.2BDifficulty 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, 9.3Difficulty 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:
>
>
>
NO21.0 ppmtriplet
2.0 ppmsextet
4.3 ppmtriplet
622
Topic: Structure Elucidation Section: 2.16, 9.2, 9.3Difficulty 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:
4-Heptanone
623
Topic: GeneralSection: 9.4Difficulty Level: Easy
130. Which form of electromagnetic radiation possesses the least energy?Ans: radiofrequency radiation
Topic: Reference CompoundSection: 9.7Difficulty 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 ExchangeSection: 9.10Difficulty 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
624
Topic: 13C NMR, Structure Elucidation Section: 9.11Difficulty Level: Medium
133. Interpret the following 13C/DEPT spectrum of a compound C5H10Br2: elucidate the structure and assign all the 13C resonances.
Ans:
Br Br
>
32 ppm
>
>
27 ppm
>
33 ppm
>
33 ppm
625
Topic: Structure ElucidationSection: 2.16, 9.2, 9.3, 9.11Difficulty 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.
626
Ans:
4-Bromotoluene
627
Topic: Structure Elucidation Section: 2.16, 9.2, 9.3. 9.11Difficulty 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.
628
Ans:
Propanoic acid
629
Topic: Structure Elucidation Section: 2.16, 9.2, 9.3, 9.11Difficulty 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:
Methyl butyrate
630
Topic: Structure Elucidation Section: 2.16, 9.2, 9.3, 9.11Difficulty 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:
1-Nitropropane
631
Topic: Structure Elucidation Section: 2.16, 9.2, 9.3, 9.11Difficulty 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:
2-Hexanone
632
Topic: Structure Elucidation Section: 2.16, 9.2, 9.3, 9.11Difficulty Level: Hard
633
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.
634
Ans:
2,6-dichlorophenol
635
Topic: Structure Elucidation Section: 2.16, 9.2, 9.3, 9.11Difficulty 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.
636
Ans:
2,6-dimethylphenol
637
Topic: Base Peak Section: 9.13Difficulty 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: 9.13Difficulty Level: Easy
142. A mass spectrometer sorts ions on the basis of their _______________.Ans: mass to charge ratio
Topic: Molecular IonSection: 9.14Difficulty 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: 9.17Difficulty 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: 9.17Difficulty 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: 9.17BDifficulty 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.)
638
639
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