1121792871 organic chemistry 1

Chapter Nine MULTIPLE CHOICE QUESTIONS Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Easy 1. How many many signals signals would would you expect expect to find find in the 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 Predict the splitting splitting pattern pattern you would observe observe for the proton at C1 of 2,3-dimethyl 2,3-dimethyl-2-2 phenylbutane.

A) B) C) D) E)

Doub Doubllet Sing Single lett Quar Quarttet Sept eptet Octet Ans: B

33

Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 3. Which one of the following following best represen represents ts the predicted predicted approximate approximate chemical chemical shift and coupling for the hydrogen(s) indicated with the arrow? O

A) B) C) D) E)

CH3

1.10 1.10 ppm, ppm, sin singl glet et 2.10 2.10 ppm, ppm, doub double lett 3.40 3.40 ppm, ppm, sin singl glet et 4.5 ppm, ppm, sin singl glet et 3.5 ppm, ppm, qua quart rtet et Ans: C


A) B) C) D) E)

1.00 1.00 ppm, ppm, sin singl glet et 2.10 2.10 ppm, ppm, sin singl glet et 2.10 2.10 ppm, ppm, qua quart rtet et 3.00 3.00 ppm, ppm, sin singl glet et 2.10 2.10 ppm, ppm, trip triple lett Ans: B

34


A) B) C) D) E)

1.00 1.00 ppm, ppm, qua quart rtet et 2.40 2.40 ppm, ppm, sin singl glet et 2.40 2.40 ppm, ppm, qua quart rtet et 3.00 3.00 ppm, ppm, qua quart rtet et 2.40 2.40 ppm, ppm, trip triple lett Ans: C


A) B) C) D) E)

1.00 1.00 ppm, ppm, qua quart rtet et 2.40 2.40 ppm, ppm, sin singl glet et 2.40 2.40 ppm, ppm, qua quart rtet et 3.00 3.00 ppm, ppm, qua quart rtet et 1.00 1.00 ppm, ppm, trip triple lett Ans: E

35

Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 7. Which one of the following following best represen represents ts the predicted predicted approximate approximate chemical chemical shift and coupling for the hydrogen(s) indicated with the arrow? H

H

A) B) C) D) E)

5.40 ppm, ppm, mult multipl iplet et 2.00 ppm, ppm, mult multipl iplet et 2.00 2.00 ppm, ppm, doub double lett 2.00 2.00 ppm, ppm, qua quart rtet et 5.40 5.40 ppm, ppm, doub double lett Ans: A

Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 8. Which one of the following following best represen represents ts the predicted predicted approximate approximate chemical chemical shift and coupling for the hydrogen(s) indicated with the arrow? H

H

A) B) C) D) E)

5.40 5.40 ppm, ppm, doub double lett 1.00 ppm, ppm, mult multipl iplet et 2.00 2.00 ppm, ppm, doub double lett 1.00 1.00 ppm, ppm, doub double lett 5.40 ppm, ppm, mult multipl iplet et Ans: D

36

Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy 9. Which one of the following following best represen represents ts the predicted predicted approximate approximate chemical chemical shift and coupling for the hydrogen(s) indicated with the arrow? N

A) B) C) D) E)

3.00 3.00 ppm, ppm, doub double lett 3.00 3.00 ppm, ppm, trip triple lett 5.00 5.00 ppm, ppm, trip triple lett 1.00 1.00 ppm, ppm, doub double lett 5.40 ppm, ppm, mult multipl iplet et 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 shift and coupling for the hydrogen(s) indicated with the arrow? N

A) B) C) D) E)

3.00 3.00 ppm, ppm, doub double lett 3.00 3.00 ppm, ppm, trip triple lett 5.00 5.00 ppm, ppm, trip triple lett 1.00 1.00 ppm, ppm, doub double lett 3.00 3.00 ppm, ppm, sin singl glet et Ans: E

37

Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Easy For the following compound how many different signals would you see in the proton NMR? (Assume that you can see them all.)

11.

A) B) C) D) E)

4 5 6 7 8 Ans: A


12.

H3CO

A) B) C) D) E)

4 5 6 7 8 Ans: C

38


13.

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) CH3CCH2CH3 H B)

C6H5CH2C H C)

O

(CH3)2CHC H D)

O

(CH 3)3CC

O

O

E)

C6H5CH2CCH3

Ans: D

39

Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Medium For the following compound how many different signals would you see in the proton NMR? (Assume that you can see them all.)

15.

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 For the following compound how many different signals would you see in the proton NMR? (Assume that you can see them all.)

16.

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 shift and coupling for the hydrogen(s) indicated with the arrow?

O

A) B) C) D) E)

CH3

1.10 1.10 ppm, ppm, sin singl glet et 2.10 2.10 ppm, ppm, trip triple lett 3.40 3.40 ppm, ppm, trip triple lett 4.5 ppm, ppm, sin singl glet et 5.3 ppm, ppm, dou doubl blet et Ans: D

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Medium 18. Predict Predict the splitting splitting pattern pattern you would observe observe for the proton at C4 of 2,3-dimethyl 2,3-dimethyl-2-2 phenylbutane.

A) B) C) D) E)

Doub Doubllet Sing Single lett Quar Quarttet Sept eptet Octet Ans: A

41

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Medium 19. 19. A) B) C) D) E)

How How man many y 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 many chemica chemicall lly y distinct distinct 1H NMR signals are there in the following compound ? ClCH2CHCH3 Br A) B) C) D) E)

1 2 3 4 5 Ans: D

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2 Difficulty Level: Medium 21. 21. A) B) C) D) E)

How How man many y 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? OCH3

22.

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-chlo 2-chlororo-4-m 4-meth ethylp ylpent entane ane B) 3-chlo 3-chlororo-2-m 2-meth ethylp ylpent entane ane C) 3-ch 3-chlo loro ropen penta tane ne D) 1-chloro-2,2 1-chloro-2,2-dime -dimethylb thylbutane utane E) 3-chlo 3-chlororo-3-m 3-meth ethylp ylpent entane ane 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 shift and coupling for the hydrogen(s) indicated with the arrow? H

H

A) B) C) D) E)

1.00 1.00 ppm, ppm, doub double lett 2.00 2.00 ppm, ppm, sin singl glet et 2.00 2.00 ppm, ppm, trip triple lett 2.00 2.00 ppm, ppm, doub double lett 1.00 1.00 ppm, ppm, trip triple lett Ans: D

43

Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Medium A compound C5H11Cl which exhibits only two singlets in the 1H NMR spectrum must 25. be: A) 1-Ch 1-Chlo loro ropen penta tane ne B) 1-Chloro-2,2 1-Chloro-2,2-dim -dimethylp ethylpropane ropane C) 1-Chlo 1-Chlororo-2-m 2-meth ethylb ylbuta utane ne D) 3-Ch 3-Chlo loro ropen penta tane ne E) 1-Chlo 1-Chlororo-3-m 3-meth ethylb ylbuta utane ne Ans: B Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Medium 26. Conside Considerr the the expe expecte cted d 1H NMR spectrum of 1,1,3,3-tetramethylcyclopentane. Which of the following is likely to be observed?

A) B) C) D) E)

7 signal signals: s: all all singl singlets ets 7 signals: signals: 4 singlet singlets, s, 3 doublets doublets 3 signal signals: s: all all singl singlets ets 3 signals: signals: one single singlet, t, 2 doublets doublets 3 signals: signals: two single singlets, ts, one one doublet doublet Ans: C

Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2 Difficulty Level: Medium 27. Conside Considerr the the expe expecte cted d 1H NMR spectrum spectrum of 2,4-dimethyl-1,4-pentadiene. 2,4-dimethyl-1,4-pentadiene. Which of the following is likely to be observed?

A) B) C) D) E)

7 signal signals: s: all all singl singlets ets 4 signal signals: s: all all singl singlets ets 3 signal signals: s: all all singl singlets ets 3 signals: signals: one single singlet, t, 2 doublets doublets 4 signals: signals: two single singlets, ts, two two doublets doublets Ans: E

Topic: Proton NMR- Symmetry, Splitting, Chemical Shift

44

Section: 9.2 Difficulty Level: Hard 28. For the C2 methyle methylene ne group in in 1-bromopropan 1-bromopropane, e, the theoreti theoretical cal multiplic multiplicity ity in the 1H NMR spectrum, presuming that Jab is sufficiently different from J bc 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 29. An organic organic compound absorbs absorbs strongly strongly in the IR IR at 1687 cm-1. Its 1H NMR spectrum consists of two signals, 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

45

Difficulty Level: Easy 30. If all the protons protons of 1-fluoropentan 1-fluoropentanee could be discerned, discerned, which would you expect expect to be 1 at the lowest field in the H NMR spectrum of this compound? CH3CH2CH2CH2CH2F

A) B) C) D) E)

V IV III II I Prot Protons ons on on carb carbon on I Proton Protonss on on carb carbon on II II Proton Protonss on carbon carbon III Proton Protonss on on carb carbon on IV IV Prot Protons ons on on carb carbon on V Ans: A

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

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

46

Difficulty Level: Easy 32. Which proton(s proton(s)) of the compound compound below would would appear as a septet septet in the 1H NMR spectrum? I CH3 CH3CH2CH2-O-CH CH3 V A) B) C) D) E)

IV II I II

II

I The proton protonss on carbon carbon I The prot protons ons on carbo carbon n II The prot protons ons on on carbon carbon III III The prot protons ons on carbo carbon n IV The proton protonss on carbon carbon V Ans: B

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2C Difficulty Level: Easy 33. Which proton(s proton(s)) of the compound compound below would would appear as a doublet doublet in the 1H NMR spectrum? I CH3 CH3CH2CH2-O-CH CH3 V A) B) C) D) E)

IV II I II

II

I The proton protonss on carbon carbon I The prot protons ons on carbo carbon n II The prot protons ons on on carbon carbon III III The prot protons ons on carbo carbon n IV The proton protonss on carbon carbon V Ans: A


47

Difficulty Level: Easy 34. Which proton(s proton(s)) of the compound compound below would would appear as a triplet triplet in the 1H NMR spectrum? I CH3 CH3CH2CH2-O-CH CH3 V A) B) C) D) E)

IV II I II

II

I The prot protons ons on carbo carbon n II The prot protons ons on on carbon carbon I and and V The proto protons ns on carbo carbon n III and and V The proto protons ns on carbo carbon n III and and IV The proton protonss on carbon carbon V Ans: C

Topic: Proton NMR- Symmetry, Splitting, Chemical shift Section: 9.2C Difficulty Level: Easy 35. Consider Consider the expected expected splitti splitting ng of signal signal “b” in the 1H NMR spectrum of 1-methoxy-2methylpropane, shown below. Presuming that Jab is sufficiently different from J bc 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


48

Difficulty Level: Medium 36. Predict Predict the splitting splitting pattern pattern you would observe observe for the proton at C3 of 2,3-dimethyl 2,3-dimethyl-2-2 phenylbutane.

A) B) C) D) E)

Doub Doubllet Sing Single lett Quar Quarttet Sept eptet Octet Ans: D

Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2C Difficulty Level: Medium 37. Which of these these compounds compounds will not be represe represented nted by a singlet singlet only in the 1H NMR spectrum? A) Neop Neopen enta tane ne B) Hexamet Hexamethyl hylbenz benzene ene C) Isob Isobut utan anee D) (Z)-1, (Z)-1,2-D 2-Dich ichlor loroet oethene hene E) (E)-1, (E)-1,2-D 2-Dich ichlor loroet oethene hene Ans: C Topic: Proton NMR- Symmetry, Splitting, Chemical Shift Section: 9.2C Difficulty Level: Hard 38. Consider Consider the expected expected splittin splitting g of the C2 proton signal signal in the 1H NMR spectrum of 1,1dibromopentane. Presuming that the 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 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 J bc and that the instrument has sufficient resolving power, what is the theoretical multiplicity of signal “b”? d H b

39.

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 Consider the expected expected splitti splitting ng of signal signal “b” in the 1H NMR spectrum of 1,1-dichloro-3methylbutane, shown below. Presuming that that Jab is sufficiently different from J bc 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

50

41. Consider Consider the expected expected splitti splitting ng of signal signal “b” in the 1H NMR spectrum of 1,2dimethoxypropane, shown below. Presuming that that J bc is sufficiently different from J bd 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 Consider the expected expected splitti splitting ng of signal signal “c” in the 1H NMR spectrum of 2-ethyl-1 butanol, shown below. Presuming that J bc is sufficiently different from J cd and that the instrument has sufficient resolving power, what is the theoretical multiplicity of signal “c”? a b a A) B) C) D) E)

OH

b

c

d

e

6 7 8 12 15 Ans: E

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

51

43. Consider Consider the expected expected splittin splitting g of the C2 proton signal 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 the theoretical theoretical multipli multiplicity city of the C-2 proton proton signal 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

52

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.2C Difficulty Level: Hard 45. Cons Consid ider er the the 1H NMR spectrum 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, 6, 4, 4, 1 3, 6, 6, 4, 4, 3 3, 12, 12, 3, 3, 1 3, 12, 12, 3, 3, 3 3, 12, 12, 6, 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 compoun ds 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


53

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 compoun ds 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 compoun ds 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

54

O

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.2A, 9.2C Difficulty Level: Medium 49. A compound compound with with the molecular molecular formul formulaa 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 structure for the compound is: CH3 A) CH3COH CH3 CH3

B)

CH3OCHOH

C) CH CH CH CH OH D) CH CH OCH CH E) CH3CHCH 2OH 3

2

3

2

2

2

2

3

CH3

Ans: D

55

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Easy 50. What is the the structure structure of the the compound compound in the followi following ng 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

56

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Easy 51. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C9H10O2? Relative integration is shown.

5 2 2 1

12

10

8

6 PPM

A)

CHO

B)

CO2H

C)

CO2H

D) HO 2C

CO2H

E)

Ans: C

57

4

2

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Easy 52. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C8H14? Relative integration is shown. 9

3 2

8

7

6

5

4 PPM

A)

B) C)

C

D)

E)

Ans: D

58

3

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Easy 53. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C6H11 N? N? In the IR spectrum you notice a stretch at about 2250 cm-1. Relative integration is shown.

6 4

1

8

7

A)

6

5

4 PPM

CN

B)

C)

CN

D)

CN

E) N

H

Ans: D

59

3

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 54. Determine Determine the most likely likely structure structure of a compound, compound, with the molecular molecular formula formula C9H12, 1 which gave a H 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 compound with with the molecular molecular formul formulaa 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

I

Cl

Cl

II

III Cl

Cl

IV A) B) C) D) E)

V


60

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 56. A compound compound with with the molecular molecular formul formulaa 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 in the IR spectrum. A possible structure structure for the compound is: O

O

Br

O

Br Br

I

II

III

O

Br Br

O

IV A) B) C) D) E)

V

I II III IV V Ans: C

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 57. A compound compound with with the molecular molecular formul formulaa C6H15 N N gave the following 1H NMR spectrum: triplet, δ 0.90 quartet, δ 2.4 There were no other signals. The most likely structure structure for the compound is: CH NCH CH A) 3 2 3 CH2CH2CH3 B) CH3NCH2CH2CH2CH3

CH3

C) CH CH CH CH CH CH NH D) CH3CH2NCH2CH3 3

2

2

2

2

2

2

CH2CH3 E) CH3CH2CH2NCH2CH2CH3

H

Ans: D

61

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 58. A compound compound with with the molecular molecular formul formulaa 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 in the IR spectrum. The most likely structure structure for the compound is: Cl O

O

O

Cl

Cl

I

II

III

O

Cl Cl

IV A) B) C) D) E)

O

V


Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 59. A compound compound with with the molecular molecular formul formulaa 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 the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C10H20? Relative integration is shown.

3 2

8

7

6

5

4 PPM

A)

B)

C)

D) E)

Ans: C

63

3

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 61. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C4H8O? Relative integration is shown.

1

8

7

6

5

4 PPM

A) O

B)

OH

OH

C)

D)

O

E)

O

Ans: D

64

1

3

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 62. What is the the structure structure of the the compound compound in the followi following ng 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

2 PPM

O

A)

O O

O

B) H

H O

O

C) O

O

O

O O

D) O

O O

E)

O O O O

Ans: A

65

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 63. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C10H11 N? N? 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 3 2

8

7

6

5

4 PPM

A)

B) NC

C) CN

D) CN H N

E)

Ans: D

66

3

2

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 64. What is the the structure structure of the the compound compound in the followi following ng 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

13

1

12

11

10

9

8

1

7

6 PPM

A)

O

HO

CO 2H

B)

O

C) D)

O CO2H

E)

CO2H

Ans: E

67

1

5

4

3

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 65. What is the the structure structure of the the compound compound in the followi following ng 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

8

2

7

A)

6

5

4 PPM

O O

B)

O

O

O

C)

O

D) O O

E) O O

Ans: A

68

2

3

2

1

0

Topic: Proton NMR- Unknown Identification. Section: 9.2, 9.3 Difficulty Level: Medium What is the structure of the compound in the following 1H-NMR spectrum with the molecular formula C12H17 NO NO and a characteristic IR stretch near 1700 cm-1 and a characteristic peak in the 13C-NMR at 170 ppm? Relative integration is shown.

66.

3

3

22

8

2

7

6

5

4 PPM

O

A)

N

B) N

O

C) N HO O

D)

N

O

E)

N

Ans: A

69

3

3 2

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 67. What is the the structure structure of the the compound compound in the followi following ng 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

3

2

1

6

5

1

4

3 PPM

A) O O

O

B) O

C) O

O

D) O

E) O

O

Ans: B

70

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 68. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C10H12O2? Relative integration is shown.

3 2

2

2

2

1

11

10

9

8

7

6 PPM

CHO

A) O O

B)

O CO 2H

C)

D)

CO2H

CO2H

E)

Ans: C

71

5

4

3

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 69. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C8H16O? Relative integration is shown. 6

3 2

2

2

1

2

1 PPM

A)

O

O

B)

H

C)

OH

D) O

E)

O

Ans: E

72

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 70. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C6H10O2? Relative integration is shown.

3 2

2

2

1

6

5

4

3 PPM

O

A)

O O

B) O

H

C) O

O O

D)

O O

E)

OH

Ans: D

73

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 71. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C9H12O? Relative integration is shown.

3 2

2

2

2

1 exchanges with D2O

7

A)

6

5

4 PPM

O

B) HO C) HO

D)

OH

E) HO

Ans: E

74

3

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 72. What is the the structure structure of the the compound compound in the followi following ng 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

8

7

1

6

5

4 PPM

A) O

B)

O

C)

O

D)

O

O

E) Ans: E

75

3

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 73. 73. A com compo poun und d C5H10O gave the following spectral data: 1 H NMR spectrum spectru m IR spectrum spectru m 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

II

I O

IV A) B) C) D) E)

O

III O

V


Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Medium 74. 74. A com compo poun und d 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 the structure structure of the the compound compound in the followi following ng 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

6

5

1

4

3 PPM

A)

O

B)

O

C) O

D) O E)

O

Ans: A

77

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 76. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C5H11 NO, NO, which shows a characteristic stretch in the IR around 1700 -1 cm , and a characteristic peak at 202 ppm in the 13C-NMR? Relative integration is shown. 6

2

2

1

10

9

A)

8

7

6

5 PPM

CHO

H2N

B) N

CHO

C) N O

D) N H

CHO

E) N

CHO

Ans: B

78

4

3

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 77. What is the the structure structure of the the compound compound in the followi following ng 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. 6

4

2

2

1

4

3

2 PPM

O

A) O

Cl O O

B) O

O Cl

O

C)

O

Cl O O

D)

O

Cl O

O

E) O

O Cl

Ans: C

79

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 78. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C6H12O2? Relative integration is shown. 3 2

10

8

6

4 PPM

A)

O O

O

B) HO

C)

O

D)

O O

E)

2

O O

Ans: D

80

3 2

2

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 79. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C6H12? Relative integration is shown.

6

3 2 1

8

7

6

5

4 PPM

A) B) C)

D) E) Ans: B

81

3

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 80. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C4H7Br? Relative integration is shown.

3 2 1 1

6

5

A) Br B)

4

3 PPM

Br

C) Br Br

D) E)

Br

Ans: C

82

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 81. What is the the structure structure of the the compound compound in the followi following ng 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.

3

3

2 1

7

1

6

5

4

3 PPM

O

A) O

B) C) O

O

D) E)

O

Ans: A

83

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 82. What is the the structure structure of the the compound compound in the followi following ng 1H-NMR spectrum with the molecular formula C5H11 NO? NO? In the 13C-NMR spectrum you notice that the farthest peak downfield has a chemical shift of 173 ppm. Relative integration is shown.

3

3 2

2

1 exchanges with D 2O

9

8

7

6

5

4 PPM

O

A)

N H O

B)

N H O

C)

N H

D)

HN O O

E) H

N

Ans: A

84

3

2

1

0

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 83. A compound compound with with the molecular molecular formul formulaa 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

IV A) B) C) D) E)

III

V


85

Topic: Proton NMR- Unknown Identification Section: 9.2, 9.3 Difficulty Level: Hard 84. Determine Determine the likely likely structur structuree for a compound compound A (C6H10O), which is found to decolorize bromine in carbon tetrachloride. Its spectral data is as follows: 1 H NMR NM R 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

I

OH

II

III

OH

OH

IV A) B) C) D) E)

V

I II III IV V Ans: C

86

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.8B Difficulty Level: Easy 85. In NMR term termino inolog logy, y, proton protonss Ha and H b are said to be: H

Cl Hb

A) B) C) D) E)

Ha

Iden Identi tica call Enant Enantio ioto topi picc Dias Diaste tere reot otop opic ic Homo Homoto topi picc Meso Mesoto topi picc Ans: C

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.8B Difficulty Level: Easy 86. In the the struc structur turee shown, shown, Ha and H b are classified as: Hb

A) B) C) D) E)

Ha

homoto homotopic pic proton protons. s. vici vicina nall proto protons ns.. enanti enantioto otopic pic prot protons ons.. diaste diastereo reotop topic ic protons protons.. isomer isomeric ic proton protons. s. Ans: C

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.8B Difficulty Level: Medium 87. In the the struc structur turee shown, shown, Ha and H b are classified as: Ha Hb

A) B) C) D) E)

homoto homotopic pic proton protons. s. vici vicina nall proto protons ns.. enanti enantioto otopic pic prot protons ons.. diaste diastereo reotop topic ic protons protons.. isomer isomeric ic proton protons. s. Ans: D

87

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.8B Difficulty Level: Medium 88. In the the struc structur turee shown, shown, Ha and H b are classified as: HO

H

Ha H b

A) B) C) D) E)

homoto homotopic pic proton protons. s. vici vicina nall proto protons ns.. enanti enantioto otopic pic prot protons ons.. diaste diastereo reotop topic ic protons protons.. isomer isomeric ic proton protons. s. Ans: D

Topic: Proton NMR- Chemical Shift, Splitting, Etc. Section: 9.8B Difficulty Level: Medium 89. In the the struc structur turee shown, shown, H b and Hc are classified as: Ha Hb Hc

A) B) C) D) E)

homoto homotopic pic proton protons. s. gemin geminal al prot proton ons. s. enanti enantioto otopic pic prot protons ons.. diaste diastereo reotop topic ic protons protons.. isomer isomeric ic proton protons. s. Ans: D

88

Topic: C-13 NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Easy 90. The broadban broadband d proton-de proton-decoup coupled led 13C NMR spectrum of a hexyl chloride ch loride exhibits five signals. Which of these structures structures could be the correct one for the compound? CH A) 3 CH3CCH2CH2Cl CH3 Cl

B)

CH3CH2CCH2CH3 CH3 CH3 CH3

C)

CH3C

CHCH3

Cl CH3

D)

CH3CHCHCH2CH3 Cl CH3

E)

CH3C

CHCH3

CH3 Cl

Ans: D Topic: C-13 NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Easy 91. How many signals signals will will be recorded recorded in the broadband broadband proton-decoupl proton-decoupled ed 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. 92. How How man many y 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. 93. How How man many y 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. 94. How How man many y 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. 95. How How man many y 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 For the following compound how many different signals would you see in the carbon NMR? (Assume that you can see them all.)

96.

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

C

X

D)

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) Hept Heptan anee B) 2-Me 2-Meth thyl ylhe hexa xane ne C) 3,3-Dim 3,3-Dimeth ethylp ylpenta entane ne D) 2,4-Dim 2,4-Dimeth ethylp ylpenta entane ne E) 2,2,3-T 2,2,3-Trim rimeth ethylbu ylbutan tanee Ans: D

92

Topic: Carbon NMR- Symmetry, Chemical Shift Section: 9.11 Difficulty Level: Medium For the following compound how many different signals would you see in the carbon NMR? (Assume that you can see them all.)

99.

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.

A) B) C) D) E)

For the following compound how many different signals would you see in the carbon NMR? (Assume that you can see them all.)

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 bromodichlorob bromodichlorobenzene enzene which gives four signals signals in the broadband proton-deco proton-decoupled upled 13 C spectrum could be: Br

Cl Br

Cl

Cl

I

Br

Cl

Cl

Cl

II

III Cl

Br

Cl

Br

Cl

IV A) B) C) D) E)

Cl

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

A) B) C) D) E)

S

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 c an separate and see all peaks.) pea ks.) Br

I

A) B) C) D) E)

II

III

I II III IV None None of of the the abov above. e. Ans: E

95

IV

Topic: Carbon NMR and Proton NMR- Symmetry, Chemical Shift Section: 9.2, 9.11 Difficulty Level: Hard

105.


I A) B) C) D) E)

II

III

IV

I II III IV More More than than one of the the above. above. Ans: C


106.


I A) B) C) D) E)

II

III

I II III IV More More than than one of the the above. above. Ans: A

96

IV


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 above fit fit the criteria. criteria. Ans: C


108.


I

A) B) C) D) E)

II

III

I II III IV None None of of the the abov above. e. Ans: D

97

IV

Topic: C-13 NMR- Symmetry, Chemical Shift Section: 9.11D Difficulty Level: Easy 109. How will the methyl methyl carbon appear appear in the proton off-resonan off-resonance ce decoupled decoupled 13C spectrum of toluene?

A) B) C) D) E)

Sing Single lett Doub Doubllet Trip Tripllet Quar Quarttet Quin Quinttet Ans: D

Topic: Mass Spectrometry Section: 9.13 Difficulty Level: Easy

110. A) B) C) D) E)

Which Which is is the the base base peak? 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 Alco Alcoho holl Ether Ketone Prim Primar ary y ami amine ne 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 struct structure ure of a compound compound C6H14 with a base peak at m/z 43. CH3CH2CH2CH2CH2CH3 (CH3CH2)2CHCH3 (CH3)3CCH2CH3 (CH3)2CHCH(CH3)2 None None of of the these se Ans: D

Topic: Mass Spectrometry Section: 9.17 Difficulty Level: Medium 115. What is the the molecular molecular formula formula of this this compound? compound?

A) B) C) D) E)

m /z 84 M+• 85 86 C5H10O C5H8O C5H24 C6H12 C4H6O2 Ans: B

intensity 10.00 0.5 6 0.0 4

Topic: Mass Spectrometry Section: 9.17 Difficulty Level: Medium 116. What is the the molecular molecular formula formula of this this compound? compound?

A) B) C) D) E)

m /z 78 M+• 79 80 81 C6H6 C3H5Cl C6H8 C6H9 C3H7Cl Ans: E

intensity 10.00 1 3 .3 0 .3

100

Topic: Mass Spectrometry Section: 9.17A Difficulty Level: Easy 117. The mass spectra spectra of alkyl bromides bromides and chlorides chlorides are characteri characterized zed by an unusually intense __________. A) bas base pea peak k B) pare parent nt peak peak + C) M • +1 peak D) M+• +2 peak E) None None of of the these se Ans: D Topic: Mass Spectrometry Section: 9.17A Difficulty Level: Hard 118. The data below below from the molecula molecularr ion region of the mass mass spectrum spectrum of a halogenhalogencontaining compound are consistent with the presence of what halogen(s) in the original compound? intensity

A) B) C) D) E)

M+• M+• +2 M+• +4 One Br One Cl One One Br and and one one Two Br Two Cl Ans: D

51.0 100.0 49.0

Cl

SHORT ANSWER QUESTIONS

Topic: General Section: 9.1 Difficulty Level: Easy 119. “NMR” stands for ________ ________________ _______________ _______.. Ans: Ans: nuclear nuclear magnet magnetic ic resona resonance nce

101

Topic: Structure Elucidation Section: 9.2 Difficulty Level: Medium 120. Briefly Briefly explain how you might might distinguish distinguish between between the following following substances substances by 1 comparing their H-NMR spectra: O O

O

O

I II Ans: The main differen difference ce would likely likely be in the chemical chemical shift shift of the methine 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 Briefly explain how you might might distinguish distinguish between between the following following substances substances by 1 comparing their H-NMR spectra: O O

O

O

I II Ans: The main differen difference ce would likely likely be in the chemical chemical shifts shifts of the methine methine proton 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

II

O O

O O

~3.5 ppm (septet) ~2.2 ppm (triplet)


103

Topic: Structure Elucidation Section: 9.2 Difficulty Level: Medium 122. Briefly Briefly explain how you might might distinguish distinguish between between the following following substances substances by 1 comparing their H-NMR spectra: O

H N

N H

O

I II Ans: The main differen difference ce would likely likely be in the chemical chemical shifts shifts of the methine methine proton 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

H N

N H

O

~3.2 ppm (septet)


~2.2 ppm (triplet) Topic: 1H NMR Section: 9.2 Difficulty Level: Medium

123. 123. Pred Predic ictt the the 1H NMR spectrum of diethoxymethane, CH3CH2OCH2OCH2CH3. Ans:

~1.2 ppm triplet

~1.2 ppm triplet

>

>

O >

~3.4 ppm quartet

O >

~4.9 ppm singlet

>

~3.4 ppm quartet

104

Topic: 1H NMR Section 9.2 Difficulty Level: Medium 124. 124. Pred Predic ictt the 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 Predict the number of signals signals in the the 1H NMR spectrum of 2-methyl-2-pentanol. Ans: Five 1

2

1' OH

4 3

5

Topic: General, Chemical Shift Section: 9.2A Difficulty Level: Medium 126. A shielded shielded proton will will absorb absorb at a higher frequency frequency (this (this is the ________ ________ end of the spectrum); and a deshielded proton will absorb at a lower frequency (the _____________ end of the spectrum). Ans: Ans: upfiel upfield; d; downfi downfield eld

105

Topic: General, Signal Integration Section: 9.2B Difficulty Level: Easy 127. When measuring measuring the integra integrall for a particular particular peak in the the NMR spectrum, spectrum, we are not interested in the peak height as much as in the ____________________. Ans: Ans: area area unde underr the the peak peak Topic: Structure Elucidation Section: 9.2, 9.3 Difficulty Level: Easy 128. 128. Exam Examin inee the the 1H NMR spectrum of 1-nitropropane, 1-nitropropane, shown below. Assign the signals to the respective hydrogen atoms in the molecule.

Ans:

4.3 ppm triplet >

1.0 ppm triplet

> >

NO2

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 structure of A by 1 13 . scrutinizing its IR, H NMR and C NMR spectra, shown below.

Ans:

O

4-Heptanone

107

Topic: General Section: 9.4 Difficulty Level: Easy 130. Which form form of electromagneti electromagneticc radiation radiation possesses possesses the least energy? energy? Ans: Ans: radiof radiofreq requen uency cy radiati radiation on Topic: Reference Compound Section: 9.7 Difficulty Level: Easy 131. What compound compound is used as the the standard standard “zero” reference reference in both both carbon and proton proton NMR? Ans: TMS or tetram tetramethyl ethylsilan silanee or (CH3)4 Si Topic: General, Bond Rotation, Proton Exchange Section: 9.10 Difficulty Level: Medium 132. Name two rapid rapid processes processes that occur occur in organic organic molecules. molecules. Ans: Rotation Rotation about C-C single single bonds; bonds; chemical chemical exchange exchange of protons protons attached attached to electronegative atoms

108

Topic: 13C NMR, Structure Elucidation Section: 9.11 Difficulty Level: Medium 133. Interp Interpret ret the the followi following ng 13C/DEPT spectrum of a compound C5H10Br 2: elucidate the structure and assign all the 13C resonances.

Ans:

32 ppm >

Br >

33 ppm

> >

27 ppm

Br

>

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 the structure structure of C by 1 13 scrutinizing its IR, H NMR and C 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 unkn unknown own compou compound, nd, F, has the formula C3H6O2. Elucidate the the structure structure of F by 1 13 scrutinizing its IR, H NMR and C 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. 136. An unk unkno nown wn comp compou ound nd,, L, has the formula C5H10O2. Elucidate the the structure structure of L by 1 13 scrutinizing its IR, H NMR and C NMR spectra, shown below.

O

Ans: O

Methyl butyrate

114

Topic: Structure Elucidation Section: 2.16, 9.2, 9.3, 9.11 Difficulty Level: Hard 137. An unkn unknown own compou compound, nd, I, has the formula C3H7 NO NO2. Elucidate the the structure structure of I by 1 13 scrutinizing its IR, H NMR and C 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 unkn unknown own compou compound, nd, E, has the formula C6H12O. Elucidate the structure of E by 1 scrutinizing its IR, H 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 unkn unknown own compou compound, nd, U, has the formula C6H4Cl2O. Elucidate the structure structure of U by 1 13 scrutinizing its IR, H NMR and C 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 unkn unknown own compou compound, nd, V, has the formula C8H10O. Elucidate the structure structure of V by 1 13 scrutinizing its IR, H NMR and C NMR spectra, shown below.

119

Ans:

OH

2,6-dimethylphenol

120

Topic: Base Peak Section: 9.13 Difficulty Level: Easy 141. In mass spectromet spectrometry, ry, the most intense intense peak is assigned assigned an intensity intensity of 100%, and is referred to as the ______________. Ans: Ans: base base peak peak Topic: m/z Ratio Section: 9.13 Difficulty Level: Easy 142. A mass spectromete spectrometerr sorts ions on the basis basis of their _______________ _______________.. Ans: Ans: mass mass to to charg chargee rati ratio o Topic: Molecular Ion Section: 9.14 Difficulty Level: Easy 143. In electron electron impact mass spectrometr spectrometry, y, a beam of high-energy high-energy electrons electrons initially initially dislodges one electron from the compound being studied. This produces a positively charged ion called the ____________________. Ans: Ans: mole molecul cular ar ion 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 approximati approximation on for the number number of carbon atoms atoms in the molecule. 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 presence of a number of differen differentt elements, elements, including including S, Br, and Cl. Topic: Nitrogen Rule Section: 9.17B Difficulty Level: Medium 146. What What is the the nitrog nitrogen en rule? rule? Ans: If the molecular molecular ion ion peak is even, the molecule molecule must contai contain n 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

1121792871 organic chemistry 1

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