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Chapter Fifteen

Topic: Spectroscopy Section: 15.1

Difficulty Level: Easy

1. Which of the following is not true about electromagnetic radiation? A) frequency is directly proportional to wavelength

B) frequency is directly proportional to energy C) frequency is inversely proportional to wavelength D) wavelength is inversely proportional to energy

E) none of these Ans: A Topic: Spectroscopy Section: 15.1

Difficulty Level: Easy

2. Which of the following electromagnetic radiation has the highest energy? A) UV B) X-ray C) IR D) microwave E) visible Ans: B Topic: Spectroscopy Section: 15.1

Difficulty Level: Easy

3. Which of the following electromagnetic radiation has the longest wavelength? A) UV B) X-ray C) IR D) microwave E) visible Ans: D Topic: Spectroscopy Section: 15.1

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4. Which of the following electromagnetic radiation has the highest frequency? A) UV B) X-ray C) IR D) microwave E) visible Ans: B Topic: Spectroscopy Section: 15.1

Difficulty Level: Medium

5. Arrange the following electromagnetic radiation in decreasing (highest to lowest) order of frequency.

IR UV

I ΙΙ III IV V

microwave γ-rays visible

A) V>III>IV>II>I B) II>V>III>IV>I C) I>IV>III>V>II D) V>II>IV>III>I E) II>IV>V>III>I Ans: B Topic: Spectroscopy Section: 15.1

Difficulty Level: Easy

6. Which of the following information is primarily obtained from infrared spectroscopy? A) arrangement of carbon and hydrogen atoms in a compound

B) molecular weight of a compound

C) conjugated π system present in a compound D) functional groups present in a compound

E) all of these Ans: D

Topic: Infrared Spectroscopy Section: 15.2

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7. Absorption of _______radiation results in vibrational excitation of the bonds in a compound. A) UV B) Microwave C) IR D) Visible E) x-ray Ans: C

Topic: Infrared Spectroscopy Section: 15.2

Difficulty Level: Easy

8. Which of the following vibrations are observed in IR spectroscopy? A) stetching B) rotational C) bending D) A & B E) A & C Ans: E

Topic: Infrared Spectroscopy Section: 15.2

Difficulty Level: Easy

9. Which of the following is currently used to indicate the location of a signal on an IR spectrum? A) wavelength B) wavenumber C) frequency D) A & B E) all of these Ans: B

Topic: Infrared Spectroscopy Section: 15.2

Difficulty Level: Easy

10. Which of the following are units for wavenumber in IR spectroscopy? A) cm—1 B) cm C) J.s—1 D) mm E) none of these Ans: A

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Topic: Signal Characteristics Section: 15.3

Difficulty Level: Easy

11. Which of the following corresponds to the functional group region on an IR spectrum? A) 1500-4000cm—1 B) 400-4000cm—1 C) 400-1500cm—1 D) 1500-2500cm—1 E) none of these Ans: A

Topic: Signal Characteristics Section: 15.3

Difficulty Level: Easy

12. Which of the following corresponds to the fingerprint region on an IR spectrum? A) 1500-4000cm—1 B) 400-4000cm—1 C) 400-1500cm—1 D) 1500-2500cm—1 E) none of these Ans: C

Topic: Signal Characteristics Section: 15.3

Difficulty Level: Medium

13. Which of the following statement(s) is(are) true about the frequency of a stretching vibration according to Hook’s law?

A) it is directly proportional to strength of the bond & the reduced mass B) it is inversely proportional to strength of the bond & the reduced mass C) it is directly proportional to strength of the bond

D) it is inversely proportional to the reduced mass E) C & D

Ans: E

Topic: Signal Characteristics Section: 15.3

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14. Rank the indicated bonds in decreasing (highest to lowest) order of wavenumber. II III H H H I A) III>II>I B) I>II>III C) II>I>III D) III>I>II E) none of these Ans: B

Topic: Signal Characteristics Section: 15.3

Difficulty Level: Easy

15. Rank the indicated bonds in decreasing (highest to lowest) order of wavenumber.

II III O H H N H I H A) III>II>I B) I>II>III C) II>I>III D) III>I>II E) none of these Ans: D

Topic: Signal Characteristics Section: 15.3

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16. Rank the indicated bonds in decreasing (highest to lowest) order of wavenumber. II III N H I O A) III>II>I B) I>II>III C) II>I>III D) III>I>II E) none of these Ans: D

Topic: Signal Characteristics Section: 15.3

Difficulty Level: Medium

17. Which one of the following compounds will have the lowest wavenumber for carbonyl absorption? O O O O O I II III IV V A) I B) II C) III D) IV E) V Ans: D

Topic: Signal Characteristics Section: 15.3

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18. Which one of the following compounds will have the lowest wavenumber for carbonyl absorption? I II III IV O O O NH2 O V O O A) I B) II C) III D) IV E) V Ans: C

Topic: Signal Characteristics Section: 15.3

Difficulty Level: Medium

19. Which one of the following compounds will have the highest wavenumber for C=C absorption? I II III IV V A) I B) II C) III D) IV E) V Ans: C

Topic: Signal Characteristics Section: 15.3

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20. Which of the following compounds will have the highest wavenumber for carbonyl absorption? O O O O O O I II III A) I B) II C) III D) II & III Ans: C

Topic: Signal Characteristics Section: 15.3

Difficulty Level: Medium

21. Arrange the indicated bonds in decreasing (highest to lowest) order of wavenumber.

I II III IV O V O O C N H A) I>V>II>IV>III B) IV>II>I>V>III C) II>I>V>III>IV D) IV>I>V>II>III E) IV>II>V>I>III Ans: E

Topic: Signal Characteristics Section: 15.4

Difficulty Level: Medium

22. Which of the following statement(s) is(are) true for an IR-active bond? A) the bond must be symmetrical

B) it must change bond length C) it must change bond angle D) it must change bond dipole

E) all of these Ans: D

Topic: Signal Characteristics Section: 15.4

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23. Which of the following bonds is IR inactive? IV III II CH3CH2 C C H I CH3CH2 C C CH2CH3 A) I B) II C) III D) I & IV E) I & III Ans: E

Topic: Signal Characteristics Section: 15.4

Difficulty Level: Medium

24. Which of the following bonds would produce the weakest absorption? A) C=C B) O—H C) C=O D) sp3C—H E) A & D Ans: A

Topic: Signal Characteristics Section: 15.4

Difficulty Level: Medium

25. Which of the following bonds would produce the strongest absorption? A) C=N B) C≡C C) C=O D) sp2C—H E) C—O Ans: C

Topic: Signal Characteristics Section: 15.4

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26. 3-hexyne does not show absorption in the range of 2000-2200 cm—1, whereas 1-hexyne does. Which of the following explains the reason for this absence of absorption for 3-hexyne?

A) it is a symmetrical compound B) there is no change in bond dipole C) there is no bond dipole

D) it is an unsymmetrical compound E) A, B & C

Ans: E

Topic: Signal Characteristics Section: 15.4

Difficulty Level: Medium

27. Which of the following alkene groups will produce the strongest signal?

F Cl Br I II III IV A) I B) II C) III D) IV Ans: A

Topic: Signal Characteristics Section: 15.5

Difficulty Level: Medium

28. Diluted alcohols show a _____absorption around 3600cm-1, due to _____. A) sharp, hydrogen bonding

B) broad, hydrogen bonding

C) sharp, absence of hydrogen bonding D) broad, absence of hydrogen bonding

Ans: C

Topic: Signal Characteristics Section: 15.5

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29. Concentrated alcohols show a _____absorption in the region of 3200-3600cm-1, due to _____.

A) sharp, hydrogen bonding B) broad, hydrogen bonding C) sharp, polarity

D) broad, polarity Ans: B

Topic: Signal Characteristics Section: 15.5

Difficulty Level: Medium

30. Carboxylic acids show a very broad absorption for the OH compared to alcohols, because they can form a ______.

A) dimer B) polymer C) trimer D) tetramer

Ans: A

Topic: Signal Characteristics Section: 15.5

Difficulty Level: Medium

31. Primary amines show two medium absorption bands around 3400 cm-1, due to _______. A) symmetric stretching

B) asymmetric stretching

C) both symmetric and asymmetric stretching D) hydrogen bonding

Ans: C

Topic: Signal Characteristics Section: 15.5

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32. How can you distinguish between cyclohexanol and cyclohexanecarboxylic acid using IR spectroscopy? OH OH O Cyclohexanecarboxylic acid Cyclohexanol

Ans: The OH absorption for the carboxylic acid is much broader than the alcoholic OH and it will also show absorption for carbonyl group.

Topic: Analyzing an IR spectrum Section: 15.6

Difficulty Level: Medium

33. Which of the following compounds will show a broad absorption around 3300 cm-1 and at 1650 cm-1? OH O O OH I II III IV O OH V A) I B) II C) III D) IV E) V Ans: D

Topic: Analyzing an IR spectrum Section: 15.6

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34. Which of the following compounds will show a sharp absorption at 3300 cm-1 and at 2150 cm-1? I II III IV C N A) I B) II C) III D) IV E) none of these Ans: A

Topic: Analyzing an IR spectrum Section: 15.6

Difficulty Level: Medium

35. Which of the following compounds will show two absorptions at 2600 cm-1 and at 2700 cm-1 along with the carbonyl absorption?

I II III IV O O O NH2 O H O A) I B) II C) III D) IV E) none of these Ans: D

Topic: Analyzing an IR spectrum Section: 15.6

Difficulty Level: Medium

36. Which of the following compounds will show absorption at 2250 cm-1?

I II III IV NH2 N H N C N A) I B) II C) III D) IV E) none of these Ans: D

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Topic: Analyzing an IR spectrum Section: 15.6

Difficulty Level: Medium

37. Which of the following compounds will have the lowest wavenumber for carbonyl absorption? O Cl O H O NH2 O OH O O I II III IV V A) I B) II C) III D) IV E) V Ans: C

Topic: Analyzing an IR spectrum Section: 15.6

Difficulty Level: Medium

38. Which of the following is true about the IR spectrum of the following compound?

Cl O A) absorptions at 1720 cm-1 & 2150 cm-1 B) absorptions at 1800 cm-1 & 2150 cm-1 C) absorptions at 1720 cm-1 & 2250 cm-1 D) absorptions at 1800 cm-1 & 2250 cm-1 E) absorptions at 1650 cm-1 & 2150 cm-1 Ans: B

Topic: Analyzing an IR spectrum Section: 15.6

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39. Which of the following compounds will show absorptions at 1640 cm-1, 2950 cm-1 and 3050 cm-1 on the IR spectrum? O O OH I II III IV V A) I B) II C) III D) IV E) V Ans: C

Topic: Analyzing an IR spectrum Section: 15.6

Difficulty Level: Medium

40. A compound with molecular formula C6H10O, shows absorptions at 1720 cm-1 and at 2980 cm-1 on the IR spectrum. Propose a possible structure for this compound. Ans:

O

Topic: Analyzing an IR spectrum Section: 15.6

Difficulty Level: Medium

41. A compound with molecular formula C3H9N, shows absorptions at 3400 cm-1 (two), 2980 cm-1 and at 1100 cm-1 on the IR spectrum. Propose a possible structure for this compound.

Ans: CH3CH2CH2NH2 Topic: Analyzing an IR spectrum Section: 15.6

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42. A compound with molecular formula C4H8O2, shows absorptions at 2200-3600 cm-1 (broad), 1720 cm-1 and at 1200 cm-1 on the IR spectrum. Propose a possible structure for this compound.

Ans:

OH O

Topic: Analyzing an IR spectrum Section: 15.6

Difficulty Level: Hard

43. Which of the following compounds will have highest wavenumber for carbonyl absorption? O O O O O O I II III O O IV A) I B) II C) III D) IV Ans: B

Topic: Analyzing an IR spectrum Section: 15.6

Difficulty Level: Hard

44. Which of the following compounds will have two absorptions at 1820 cm-1 and 1740cm-1? I II III IV O O O O O OH O NH2 O Cl O V A) I B) II C) III D) IV E) V Ans: D

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Topic: Analyzing an IR spectrum Section: 15.6

Difficulty Level: Medium

45. Which one of the following compounds is consistent with the following IR spectrum?

SDBS: National Institute of Advanced Industrial Science and Technology

O OH I II III IV O OH OH OH O H OH V A) I B) II C) III D) IV E) V Ans: D

Topic: Analyzing an IR spectrum Section: 15.6

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46. Which one of the following compounds is consistent with the following IR spectrum?

SDBS: National Institute of Advanced Industrial Science and Technology

O NH2 I II III IV N H N O NH2 N O OH V HN A) I B) II C) III D) IV E) V Ans: B

Topic: Analyzing an IR spectrum Section: 15.6

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47. Which one of the following compounds is consistent with the following IR spectrum?

SDBS: National Institute of Advanced Industrial Science and Technology

I II III IV OH C OH N OH HO C O N A) I B) II C) III D) IV E) V Ans: A

Topic: Analyzing an IR spectrum Section: 15.6

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48. Which one of the following compounds is consistent with the following IR spectrum?

SDBS: National Institute of Advanced Industrial Science and Technology

H O O O OH I II III IV H O V A) I B) II C) III D) IV E) V Ans: D

Topic: Analyzing an IR spectrum Section: 15.6

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49. Which one of the following compounds is consistent with the following IR spectrum?

SDBS: National Institute of Advanced Industrial Science and Technology

OH O OH O OH I II III IV OH V OH A) I B) II C) III D) IV E) V Ans: E

Topic: Analyzing an IR spectrum Section: 15.6

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50. Which one of the following compounds is consistent with the following IR spectrum?

SDBS: National Institute of Advanced Industrial Science and Technology

NH2 CH3 NHCH3 NH2 NH2 CH3 CH3 N(CH3)2 I II III IV V A) I B) II C) III D) IV E) V Ans: B

Topic: Analyzing an IR spectrum Section: 15.6

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51. For the following reaction, which of the following is consistent with the IR spectrum of the product? CN 2. Η3Ο+ O H 1. DIBAH

A) absorption at 2250 cm-1 should disappear

B) absorption at 3200-3400 cm-1 and 1720cm-1 should appear

C) absorption at 2250 cm-1 should disappear, new absorption at 2600-2800 cm-1 and 1720 cm-1 should appear.

D) absorption at 2250 cm-1 should disappear and absorption around 3400 cm-1 should appear.

E) none of these Ans: C

Topic: Analyzing an IR spectrum Section: 15.6

Difficulty Level: Medium

52. For the following reaction, which of the following is consistent with the IR spectrum of the product?

H3O+

O

A) absorption at 2150 cm-1 should disappear

B) absorption at 3300 cm-1 and 2150cm-1 should disappear

C) absorption at 2250 cm-1 should disappear, new absorption at 3300 cm-1 should appear D) absorption at 1650 cm-1 should disappear and absorption at 3300 cm-1 should appear

E) absorption at 3300 cm-1 and 2150cm-1 should disappear, a new absorption at 1720 cm-1 should appear

Ans: E

Topic: Analyzing an IR spectrum Section: 15.6

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53. For the following reaction, which of the following is consistent with the IR spectrum of the product?

1. NaH

OH OCH2CH3

2. CH3CH2Br

A) absorption at 3200-3600 cm-1 should disappear

B) absorption at 3200-3600 cm-1 and 1100 cm-1 should disappear

C) absorption at 1100 cm-1 should disappear and absorption at 3100 cm-1 should appear D) absorption at 1650 cm-1 should disappear and absorption at 3300 cm-1 should appear.

E) none of these Ans: A

Topic: Analyzing an IR spectrum Section: 15.7

Difficulty Level: Hard

54. Predict the product for the following reaction and explain how you will use IR spectroscopy to monitor the progress of the reaction.

1-pentyne 1. NaNH2 2. CH3CH2Br

Ans: CH3CH2CH2C≡CCH2CH3

Absorptions for spC-H around 3300 cm-1 and C≡C around 2150 cm-1 should disappear from the product IR.

Topic: Analyzing an IR spectrum Section: 15.7

Difficulty Level: Hard

55. Predict the product for the following reaction and explain how you will use IR spectroscopy to monitor the progress of the reaction.

1. CH3CH2MgBr 2. H2O

O

Ans: HO

Absorptions for C=O around 1720 cm-1 would disappear and a new absorption for OH at 3200-3600 cm-1 would appear from the product IR

Topic: Mass Spectrometry Section: 15.8

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56. Mass spectrometry is primarily used to determine: A) molecular formula of a compound

B) molecular weight of a compound C) conjugation in a compound D) A & B

E) A & C Ans: D

Topic: Mass Spectrometry Section: 15.8

Difficulty Level: Easy

57. Which of the following is initially produced when a compound is bombarded with high energy electrons? A) anion B) free radical C) radical cation D) cation E) none of these Ans: C

Topic: Mass Spectrometry Section: 15.8

Difficulty Level: Easy

58. Which of the following is not true about the molecular ion in mass spectrometry? A) The molecular ion is produced by loss of one electron from the molecule.

B) The mass of the molecular ion is equivalent to the mass of the molecule. C) The ion is produced by a loss of pair of electrons from the molecule. D) The molecular ion is often unstable and can undergo fragmentation.

E) none of these Ans: C

Topic: Mass Spectrometry Section: 15.8

Difficulty Level: Easy

59. Which of the following is always true about the base peak in a mass spectrum? A) peak corresponding to molecular ion

B) peak corresponding to the most abundant ion C) peak corresponding to lowest m/z

D) A & C E) none of these

Ans: B

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Section: 15.8

Difficulty Level: Easy

60. The separation of ions in the mass spectrometer is done by their ______. A) electrons to protons ratio

B) mass to neutrons ratio C) protons to neutrons ratio D) mass to charge ratio

E) none of these Ans: D

Topic: Analyzing M+• peak Section: 15.9

Difficulty Level: Easy

61. Which of the following is true about CH3CH3+•? A) it is the parent ion of ethane

B) it is a molecular ion of ethane with m/z =30 C) it is a fragment of propane

D) A & B E) none of these

Ans: D

Topic: Analyzing M+• peak Section: 15.9

Difficulty Level: Easy

62. Which of the m/z values corresponds to the base peak in the following mass spectrum?

A) 45 B) 44 C) 29 D) 15 E) none of these Ans: C

Topic: Analyzing M+• peak Section: 15.9

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Difficulty Level: Easy

63. Which of the m/z values correspond to the molecular ion peak in the following mass spectrum? A) 45 B) 44 C) 29 D) 15 E) none of these Ans: B

Topic: Analyzing M+• peak Section: 15.9

Difficulty Level: Medium

64. Which of the m/z values correspond to the molecular ion for the following compound?

OH A) 18 B) 82 C) 100 D) 102 E) 103 Ans: D

Topic: Analyzing M+• peak Section: 15.9

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65. Which of the following compounds will have odd m/z value for the molecular ion? H O H N O N N Br Br I II III IV A) I B) II C) III D) IV E) none of these Ans: B

Topic: Analyzing M+• peak Section: 15.9

Difficulty Level: Medium

66. Which of the following is true about the molecular weight and the M+-m/z value for the following compound?

NH2

Cl

A) odd molecular weight, m/z-115 B) odd molecular weight, m/z-121 C) even molecular weight, m/z-96 D) even molecular weight, m/z-132

E) none of these Ans: B

Topic: Analyzing (M+1)+ peak Section: 15.10

Difficulty Level: Medium

67. Which of the following is true about the (M+1)+ peak on the mass spectrum of a hydrocarbon?

A) it is the most abundant peak

B) it is due to the 13C isotope of carbon

C) it has a m/z value lower than the molecular ion D) it is useful in calculating number of carbon atoms

E) B & D Ans: E

Topic: Analyzing (M+1)+• peak Section: 15.10

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68. Which molecular formula is consistent with the following mass spectrum data? M+•at m/z= 84, relative height=10.0% (M+1)+•at m/z= 85, relative height=0.56% A) C5H10O B) C5H8O C) C5H24 D) C6H12 E) C4H6O2 Ans: B

Topic: Analyzing (M+1)+• peak Section: 15.10

Difficulty Level: Medium

69. Which molecular formula is consistent with the following mass spectrum data? M+at m/z= 72, relative height=73.0% (M+1)+at m/z= 73, relative height=3.3% A) C4H10O B) C4H9N C) C5H12 D) C4H8O E) none of these Ans: D

Topic: Analyzing (M+1)+ peak Section: 15.10

Difficulty Level: Medium

70. Provide a molecular formula that is consistent with the following mass spectrum data. M+•at m/z= 73, relative height=86.1%

(M+1)+•at m/z= 74, relative height=3.2% Ans: C3H7NO

Topic: Analyzing (M+1)+• peak Section: 15.10

Difficulty Level: Hard

71. Provide a molecular formula that is consistent with the following mass spectrum data. M+•at m/z= 136, relative height=65.6%

(M+1)+•at m/z= 137, relative height=6.2% Ans: C9H12O

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Topic: Analyzing (M+1)+• peak Section: 15.10

Difficulty Level: Hard

72. Provide a molecular formula that is consistent with the following mass spectrum data. M+•at m/z= 167, relative height=50.0%

(M+1)+•at m/z= 168, relative height=4.4% Ans: C8H9NO3

Topic: Analyzing (M+2)+• peak Section: 15.11

Difficulty Level: Medium

73. Compounds containing chlorine or bromine usually show a strong _____peak. A) molecular ion B) base C) M+1 D) M+2 E) all of these Ans: D

Topic: Analyzing (M+2)+• peak Section: 15.11

Difficulty Level: Medium

74. Which of the following will produce M+ and (M+2)+ peaks of equal intensity? A) nitrogen B) chlorine C) bromine D) oxygen E) B & C Ans: C

Topic: Analyzing (M+2)+ peak Section: 15.11

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75. Presence of bromine produces M+

• and (M+2)+• peaks of equal intensity on a mass spectrum because:

A) 81Br isotope has higher natural abundance than 79Br isotope B) 79Br and 81Br isotopes have almost equal natural abundance C) 79Br isotope has higher natural abundance than 81Br isotope D) none of these

Ans: B

Topic: Analyzing (M+2)+• peak Section: 15.11

Difficulty Level: Medium

76. Which molecular formula is consistent with the following mass spectrum data? M+•at m/z= 78, relative height=23.5% (M+1)+•at m/z= 79, relative height=0.78% (M+2)+•at m/z= 80, relative height=7.5% A) C6H6 B) C3H7Cl C) C6H8 D) C6H9Cl E) none of these Ans: B

Topic: Analyzing (M+2)+ peak Section: 15.11

Difficulty Level: Medium

77. Which molecular formula is consistent with the following mass spectrum data? M+•at m/z= 108, relative height=61.5% (M+1)+•at m/z= 109, relative height=1.5% (M+2)+•at m/z= 110, relative height=61.3% A) C2H5Br B) C5H12Cl C) C8H12 D) C2H7Br E) none of these Ans: A

Topic: Analyzing (M+2)+• peak Section: 15.11

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78. For which of the following compounds will the (M+2)+

• peak intensity be around 25% of the intensity of the molecular ion peak?

A) CH3CH2CH2Br B) CH3CH2CH2OH C) CH3CH2CH2Cl D) CH3CH2CH2NH2 E) none of these Ans: C

Topic: Analyzing (M+2)+• peak Section: 15.11

Difficulty Level: Medium

79. Which of the following mass spectra shows the presence of bromine in a compound?

I II

III IV

Four spectra above: courtesy of SDBS: National Institute of Advanced Industrial Science and Technology A) I B) II C) III D) IV E) none of these Ans: A

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Topic: Analyzing the fragments Section: 15.12

Difficulty Level: Medium

80. Which of the following compounds will produce a prominent (M-18) peak in the mass spectrum? A) 2-methylheptane B) 1-heptanol C) heptanamine D) heptanal E) none of these Ans: B

Topic: Analyzing the fragments Section: 15.12

Difficulty Level: Medium

81. Which of the following compounds will produce a prominent (M-15) peak in the mass spectrum? A) 2-methylheptane B) 1-heptanol C) heptanamine D) 1-chloroheptane E) none of these Ans: A

Topic: Analyzing the fragments Section: 15.12

Difficulty Level: Medium

82. Which of the following is not a prominent peak in the mass spectrum of 2-methyl-2-pentanol? A) (M-15) B) (M-18) C) (M-29) D) (M-16) E) none of these Ans: D

Topic: Analyzing the fragments Section: 15.12

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83. Which of the following compounds will have a prominent peak at (M-127)? A) CH3CH2CH2I B) (CH3CH2)3CCH2Cl C) (CH3)3CCH2CH2Br D) (CH3)2CHCH(CH3)2 E) none of these Ans: A

Topic: Analyzing the fragments Section: 15.12

Difficulty Level: Medium

84. Which of the following compounds will have a base peak at m/z=43? A) CH3CH2CH2CH2CH2CH3 B) (CH3CH2)2CHCH3 C) (CH3)3CCH2CH3 D) (CH3)2CHCH(CH3)2 E) none of these Ans: D

Topic: Analyzing the fragments Section: 15.12

Difficulty Level: Medium

85. Which of the following is the base peak in the mass spectrum of 2,2,4-trimethylpentane? A) 114 B) 57 C) 42 D) 29 E) none of these Ans: B

Topic: Analyzing the fragments Section: 15.12

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86. Which of the following is expected to be the base peak in the mass spectrum of CH3(CH2)4OH? A) 88 B) 55 C) 42 D) 31 E) none of these Ans: C

Topic: Analyzing the fragments Section: 15.12

Difficulty Level: Medium

87. Which of the following is expected to be the base peak in the mass spectrum of 2-methyl-2-butanol? A) 73 B) 55 C) 43 D) 31 E) 59 Ans: E

Topic: Analyzing the fragments Section: 15.12

Difficulty Level: Medium

88. Which of the following is expected to be the base peak in the mass spectrum of CH3CH2NH2? A) 15 B) 28 C) 30 D) 45 E) none of these Ans: C

Topic: Analyzing the fragments Section: 15.12

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89. Provide the structures of the fragments that result when the molecular ion of 2-heptanone undergoes fragmentation via McLafferty rearrangement.

Ans:

O H

+

Topic: Analyzing the fragments Section: 15.12

Difficulty Level: Medium

90. Provide the structure of the major fragment that results when the molecular ion of (CH3)2CHCH2CH2NH2 undergoes fragmentation.

Ans: N H

H

Topic: Analyzing the fragments Section: 15.12

Difficulty Level: Medium

91. Provide the structure of the major fragment that results when the molecular ion of CH3CH2CH2CH2OH undergoes fragmentation via alpha cleavage.

Ans: O

H

Topic: Analyzing the fragments Section: 15.12

Difficulty Level: Medium

92. Which of the following is expected to be the base peak in the mass spectrum of pentanal? CH3CH2CH2CH2CH O pentanal A) 29 B) 41 C) 44 D) 58 E) 86 Ans: C

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Topic: Analyzing the fragments Section: 15.12

Difficulty Level: Medium

93. Which one of the following compounds is consistent with the mass spectrum below?

SDBS: National Institute of Advanced Industrial Science and Technology A) CH3CH2CH(CH3)2 B) CH3CHOHCH2CH3 C) CH3CH2OCH2CH3 D) CH3CH2NHCH2CH3 E) none of these Ans: D

Topic: Analyzing the fragments Section: 15.12

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94. Which one of the following compounds is consistent with the mass spectrum below?

SDBS: National Institute of Advanced Industrial Science and Technology A) CH3CH2CH(CH3)2 B) CH3CHOHCH2CH3 C) CH3CH2OCH2CH3 D) CH3CH2NHCH2CH3 E) none of these Ans: B

Topic: Analyzing the fragments Section: 15.12

Difficulty Level: Medium

95. Which one of the following compounds is consistent with the mass spectrum below?

SDBS: National Institute of Advanced Industrial Science and Technology A) CH3CH2CH(CH3)2 B) CH3CHOHCH2CH3 C) CH3CH2OCH2CH3 D) CH3CH2NHCH2CH3 E) none of these Ans: A

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Topic: High-resolution mass spectrometry Section: 15.13

Difficulty Level: Easy

96. High-resolution mass spectrometry is used to determine the _____ of a compound. A) degree of unsaturation B) molecular formula C) molecular weight D) B & C E) none of these Ans: B

Topic: High-resolution mass spectrometry Section: 15.13

Difficulty Level: Medium

97. How will you distinguish between the following compounds using high-resolution mass spectrometry? II I O O Cl Ans: Compound I: m/z at 102.0678 Compound II: m/z at 102.0235 Topic: High-resolution mass spectrometry Section: 15.13

Difficulty Level: Medium

98. How will you distinguish between the following compounds using high-resolution mass spectrometry?

OH

I II

Ans: Compound I: m/z at 98.0729 Compound II: m/z at 98.1092 Topic: Gas chromatography-mass spectrometry Section: 15.14

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99. GC-mass spectrometry is used to find the _________ of each compound in a __________.

A) molecular formula, mixture of alkanes B) molecular weight, mixture of compounds C) molecular formula, mixture of compounds D) B & C

E) none of these Ans: B

Topic: High-resolution mass spectrometry Section: 15.15

Difficulty Level: Medium

100. Electrospray ionization is used to obtain mass spectra of proteins because: A) it allows for faster fragmentation of molecular ion

B) the molecular ion usually does not undergo fragmentation C) it allows for slow fragmentation of molecular ion

D) none of these Ans: B

Topic: Hydrogen deficiency index Section: 15.16

Difficulty Level: Easy

101. Calculate the degree of unsaturation for C9H11N. A) 4 B) 6 C) 2 D) 5 E) none of these Ans: D

Topic: Hydrogen deficiency index Section: 15.16

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102. Calculate the degree of unsaturation for C14H14N2O. A) 4 B) 6 C) 8 D) 10 E) 9 Ans: E

Topic: Hydrogen deficiency index Section: 15.16

Difficulty Level: Easy

103. Calculate the degree of unsaturation for C11H8ClBrO. A) 4 B) 6 C) 7 D) 8 E) 10 Ans: C

Topic: Hydrogen deficiency index Section: 15.16

Difficulty Level: Medium

104. Calculate the degree of unsaturation for C5H5Br2NO. A) 4 B) 6 C) 2 D) 3 E) 7 Ans: D

Topic: Hydrogen deficiency index Section: 15.16

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105. Which of the following compounds have the same degree of unsaturation? C8H10BrIO C5H5Br2NO C6H5Br I II III C9H11NO IV A) I & II B) I & III C) III & IV D) II & III E) none of these Ans: B

Topic: Hydrogen deficiency index Section: 15.16

Difficulty Level: Medium

106. Propose a possible structure for a compound with molecular formula C6H5Br

Ans: Br

Topic: Hydrogen deficiency index Section: 15.16

Difficulty Level: Medium

107. Propose all possible structures for a compound with molecular formula C4H9N that shows two medium absorptions at 3400 cm-1 and no absorption in the range of 1600-1800 cm-1 in its IR spectrum.

Ans: NH2

NH2

Topic: Hydrogen deficiency index Section: 15.16

Difficulty Level: Medium

108. Propose possible structure(s) for a compound with molecular formula C4H7N that shows absorption at 2250 cm-1 in its IR spectrum.

Ans: CH3CH2CH2C≡N Topic: Hydrogen deficiency index Section: 15.16

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109. Propose a possible structure for a compound with molecular formula C5H8O2 that shows absorption at 1720 cm-1 and no absorption in the range of 1500-1700 cm-1 or 2600-2800 cm-1 in its IR spectrum.

Figure

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