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Chapter Nine MULTIPLE 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

545

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

A) B) C) D) E)

CH3

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

546

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

547

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

548

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

549

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

550

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 ( 9-10) singlet is observed in the 1H NMR spectrum of: O A) B)

CH3CCH2CH3 H

C6 H5 CH2C H

O

C)

(CH3)2CHC H

O

D) E)

(CH 3 )3 CC O

O

C6H5CH2CCH3

Ans: D

551

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

552

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

A) B) C) D) E)

CH3

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

553

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

554

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Medium 22. How many 1H NMR signals would you expect from this compound? 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

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) 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

Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Medium 25. A compound C5H11Cl which exhibits only two singlets in the 1H NMR spectrum must be: A) 1-Chloropentane B) 1-Chloro-2,2-dimethylpropane C) 1-Chloro-2-methylbutane D) 3-Chloropentane E) 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

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) 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 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?

A) B) C) D) E)

CH3

CH2

CH2

c

b

a

Br

2 5 6 8 12 Ans: E

Topic: Structure Elucidation Section: 2.16, 9.2 Difficulty 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? O O

I

II

IV A) B) C) D) E)

O

III

V

I II III IV V Ans: A

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2A 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? CH3CH2CH2CH 2CH2F

A) B) C) D) E)

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

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2A Difficulty Level: Hard

558

31. The 1H NMR signal for which of the indicated protons occurs farthest downfield? III Cl

H

H

C C C

C CH3

I

H

IV

II V A) B) C) D) E)

I II III IV V Ans: E

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2C 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 II V IV III 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

559

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 II V IV III 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 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 II V IV III 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

560

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)

b

O

c

d

8 9 12 21 24 Ans: D

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2C 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

561

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 Difficulty Level: Hard

562

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)

c

e

2 5 6 8 12 Ans: 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 A) B) C) D) E)

b

c

d

Cl

8 9 12 18 21 Ans: E

Topic: Proton NMR- Symmetry, Splitting, Chemical shift Section: 9.2C Difficulty Level: Hard

563

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 A) B) C) D) E)

O

b

O

e

d

2 5 6 8 12 Ans: 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)

b

c

OH

d

e

6 7 8 12 15 Ans: E

Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2C Difficulty Level: Hard

564

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

A) B) C) D) E)

OH

1 6 7 8 9 Ans: C

565

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

I

II

III

O

O

O

O

IV A) B) C) D) E)

V

I II III IV V Ans: E

566

O

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

II

III

O

O

O

O

IV A) B) C) D) E)

V

I II III IV V Ans: B

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

I

II

III

O

O

O

O

IV A) B) C) D) E)

V

I II III IV V Ans: D

567

O

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 3.5 and a triplet at  1.1. The most likely structure for the compound is: CH3 A) CH3COH

B)

CH3 CH 3 CH3OCHOH

C) CH3CH2CH2CH2OH D) CH3CH2OCH2CH3 E) CH3CHCH2OH CH3

Ans: D

568

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

3

2

3

A)

O

B)

O

2 PPM

O

O

C)

O O O

D)

O

E) O

O

Ans: C

569

1

0

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 2 1

12

10

8

6 PPM

A)

CHO

B)

CO2 H

C)

CO2 H

D) HO2 C

CO2H...