Chapter 9



Chapter 9

Multiple Choice Questions:

Topic: Addition Reaction Mechanisms

Section: 9.1

Difficulty Level: Easy

1. In an addition reaction to an alkene, the π bond plays the role of:

A) nucleophile

B) electrophile

C) leaving group

D) A and B

E) B and C

Ans: A

Topic: Addition Reaction Mechanisms

Section: 9.1

Difficulty Level: Moderate

2. Addition reactions of alkenes are characterized by:

A) formation of a π bond

B) addition of two groups across a double bond

C) breaking of a π bond

D) A and B

E) B and C

Ans: E

Topic: Addition vs. Elimination Thermodynamic Perspective

Section: 9.2

Difficulty Level: Easy

3. The decrease in entropy (the (S value is negative) observed for alkene addition reactions results from:

A) the breaking of a π and ( bond.

B) the formation of two ( bonds.

C) the reaction being exothermic.

D) two molecules reacting to form a single molecule.

E) the temperature dependence of the (S term.

Ans: D

Topic: Addition vs. Elimination Thermodynamic Perspective

Section: 9.2

Difficulty Level: Easy

4. In a reaction where addition and elimination reactions are in competition, which of the following statements is most correct?

A) Addition and elimination reactions are favored at low temperatures.

B) Addition and elimination reactions are favored at high temperatures.

C) Only addition reactions are favored at low temperatures.

D) Only elimination reactions are favored at low temperatures.

E) Addition and elimination reactions are disfavored at low temperatures.

Ans: C

Topic: Addition vs. Elimination Thermodynamic Perspective

Section: 9.2

Difficulty Level: Easy

5. Which statement is true about the temperature dependence of an addition reaction?

A) Addition reactions are thermodynamically favorable at all temperatures.

B) Addition reactions are thermodynamically disfavored at all temperatures.

C) Addition reactions are thermodynamically favorable at low temperatures.

D) Addition reactions are thermodynamically favorable at high temperatures.

E) Addition reactions are thermodynamically impossible.

Ans: C

Topic: Addition vs. Elimination Thermodynamic Perspective

Section: 9.2

Difficulty Level: Moderate

6. For an addition reaction, why does the free energy term, (G, become more positive with increasing temperature?

A) The positive entropy term dominates at high temperature.

B) The negative entropy term dominates at high temperature.

C) The positive enthalpy term dominates at high temperature.

D) The negative enthalpy term dominates at high temperature.

E) The enthalpy and entropy terms cancel at high temperature.

Ans: A

Topic: Addition vs. Elimination Thermodynamic Perspective

Section: 9.2

Difficulty Level: Hard

7. Addition reactions are favorable at low temperatures because:

A) the positive enthalpy term is larger than the negative entropy term.

B) the negative enthalpy term is larger than the positive entropy term.

C) the positive enthalpy term is smaller than the negative entropy term.

D) the negative enthalpy term is smaller than the positive entropy term.

E) the enthalpy and entropy terms are equal.

Ans: B

Topic: Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

8. Which of the molecules below would be the expected product for hydrohalogenation of the following alkene:

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: E

Topic: Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

9. In the addition reaction of HI to 2-methyl-2-butene, the Markovnikov addition mechanism involves:

A) attack of 2-methyl-2-butene initiated by an iodide ion.

B) attack of 2-methyl-2-butene initiated by an iodine atom.

C) isomerization of 2-iodo-2-methylbutene.

D) formation of a carbocation at carbon two (C-2).

E) formation of carbocation at carbon three (C-3).

Ans: D

Topic: Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

10. The expected Markovnikov addition product of HI to 2-methyl-2-butene is:

A) 2-iodopentane

B) 2-iodo-2-methylbutane

C) 1-iodo-2-methylbutane

D) 2-iodo-1-methylbutane

E) 3-iodo-2-methylbutane

Ans: B

Topic: Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

11. The regioselectivity and stereospecificity in hydrohalogenation of an alkene is best described as:

A) Markovnikov orientation with syn-addition

B) Markovnikov orientation with anti-addition

C) anti-Markovnikov orientation with syn-addition

D) anti-Markovnikov orientation with anti-addition

E) Markonikov orientation with both syn- and anti-addition

Ans: E

Topic: Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

12. Which of the structures shown depicts the most stable carbocation intermediate formed in a hydrohalogenation reaction?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: B

Topic: Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

13. What compound is the expected product upon Markovnikov hydrohalogenation with HBr of the alkene shown below?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: B

Topic: Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

14. The expected major product of the following reaction is:

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: C

Topic: Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

15. The expected major product of the following reaction is:

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: A

Topic: Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

16. What is the expected major product for the following reaction?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: D

Topic: Anti-Markovnikov Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

17. Which of the molecules below arises from anti-Markovnikov hydrohalogenation with HBr of the alkene shown?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: C

Topic: Stereochemistry of Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

18. Which of the alkenes shown below would produce a chirality center upon hydrohalogenation?

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: B

Topic: Stereochemistry of Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

19. What is the major product for the following reaction?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: A

Topic: Stereochemistry of Hydrohalogenation

Section: 9.3

Difficulty Level: Moderate

20. Which of the alkenes below would be expected to produce a chirality center upon hydrohalogenation in the presence of peroxide?

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: B

Topic: Hydrohalogenation

Section: 9.3

Difficulty Level: Moderate

21. Which of the given reaction schemes would produce the molecule shown below?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) Both A and B

E) Both B and C

Ans: E

Topic: Stereochemistry of Hydrohalogenation

Section: 9.3

Difficulty Level: Moderate

22. Which of the molecules below are enantiomers, formed as products upon reaction of HBr with 4-methylpent-1-ene?

[pic]

A) I and II

B) II and III

C) III and IV

D) I and III

E) II and IV

Ans: E

Topic: Hydrohalogenation and Carbocation Rearrangements

Section: 9.3

Difficulty Level: Moderate

23. Which of the following carbocations is likely to undergo rearrangement through a methyl shift?

[pic]

A) I

B) II

C) III

D) I and II

E) II and III

Ans: D

Topic: Hydrohalogenation and Carbocation Rearrangements

Section: 9.3

Difficulty Level: Moderate

24. Which of the following carbocations is likely to undergo rearrangement through a hydride shift?

[pic]

A) I

B) II

C) III

D) I and II

E) II and III

Ans: D

Topic: Hydrohalogenation and Carbocation Rearrangements

Section: 9.3

Difficulty Level: Moderate

25. The expected major product(s) of HCl addition to the alkene shown would be:

[pic]

A) I and II

B) II and III

C) I and IV

D) V

E) All of the above are equally likely to form

Ans: A

Topic: Hydrohalogenation and Carbocation Rearrangements

Section: 9.3

Difficulty Level: Moderate

26. The expected major product(s) of HBr addition to the alkene shown would be:

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: A

Topic: Stereochemistry of Hydrohalogenation and Carbocation Rearrangements

Section: 9.3

Difficulty Level: Moderate

27. The reaction shown below would be expected to produce as major products which of the following compounds?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: D

Topic: Hydrohalogenation and Carbocation Rearrangements

Section: 9.3

Difficulty Level: Hard

28. What is the IUPAC name of the expected major product formed upon reaction of HCl with 3-methyl-1-butene?

A) 1-Chloro-2-methylbutane

B) 1-Chloro-3-methylbutane

C) 2-Chloro-2-methylbutane

D) 2-Chloro-3-methylbutane

E) 1-Chloropentane

Ans: C

Topic: Hydrohalogenation and Carbocation Rearrangements

Section: 9.3

Difficulty Level: Hard

29. Select the expected major product(s) of the following reaction:

[pic]

A) [pic]

B) [pic]

C) [pic]

D) A and B

E) A and C

Ans: C

Topic: Hydrohalogenation and Carbocation Rearrangements

Section: 9.3

Difficulty Level: Hard

30. Identify the expected product(s) for the reaction shown below?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: C

Topic: Acid Catalyzed Hydration

Section: 9.4

Difficulty Level: Easy

31. The regioselectivity and stereospecificity in the acid-catalyzed hydration of an alkene is best described as:

A) Markovnikov orientation with syn-addition

B) Markovnikov orientation with anti-addition

C) anti-Markovnikov orientation with syn-addition

D) anti-Markovnikov orientation with anti-addition

E) Markonikov orientation with both syn- and anti-addition

Ans: E

Topic: Acid Catalyzed Hydration

Section: 9.4

Difficulty Level: Easy

32. The expected major product of the following reaction is:

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: D

Topic: Acid Catalyzed Hydration

Section: 9.4

Difficulty Level: Easy

33. The expected major product of the following reaction is:

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: C

Topic: Acid Catalyzed Hydration

Section: 9.4

Difficulty Level: Easy

34. The expected major product of the following reaction is:

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: D

Topic: Acid Catalyzed Hydration

Section: 9.4

Difficulty Level: Easy

35. Treatment of 1-methylcyclohexene with H3O+ would be expected to yield as the major product which of the molecules below?

[pic]

A) I and III

B) II

C) III and V

D) IV

E) I, III and V

Ans: D

Topic: Acid Catalyzed Hydration

Section: 9.4

Difficulty Level: Moderate

36. Treatment of (S)-6-chloro-1-methyl-1-cyclohexene with H3O+ is expected to produce which of the following?

[pic]

A) I and III

B) II

C) III and V

D) IV

E) I, III and V

Ans: B

Topic: Acid Catalyzed Hydration

Section: 9.4

Difficulty Level: Hard

37. What is the expected major product for the following reaction?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: A

Topic: Oxymercuration-Demercuration

Section: 9.5

Difficulty Level: Easy

38. The regioselectivity and stereospecificity in the oxymercuration-demercuration of an alkene is best described as:

A) Markovnikov orientation with syn-addition

B) Markovnikov orientation with anti-addition

C) anti-Markovnikov orientation with syn-addition

D) anti-Markovnikov orientation with anti-addition

E) Markonikov orientation with both syn- and anti-addition

Ans: B

Topic: Oxymercuration-Demercuration

Section: 9.5

Difficulty Level: Easy

39. What is the expected major product for the following reaction?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: B

Topic: Oxymercuration-Demercuration

Section: 9.5

Difficulty Level: Easy

40. What synthetic goal is achieved by subjecting an alkene to an oxymercuration-demercuration reaction sequence?

A) Markovnikov addition of H2O, promoting skeletal rearrangement

B) Markovnikov addition of H2O, preventing skeletal rearrangement

C) anti-Markovnikov addition of H2O, promoting skeletal rearrangement

D) anti-Markovnikov addition of H2O, preventing skeletal rearrangement

E) anti-Markovnikov addition of H2O, syn-hydroxylation

Ans: B

Topic: Oxymercuration-Demercuration

Section: 9.5

Difficulty Level: Easy

41. What is the expected major product for the following reaction?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: C

Topic: Oxymercuration-Demercuration

Section: 9.5

Difficulty Level: Easy

42. What is the expected major product for the following reaction?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: D

Topic: Oxymercuration-Demercuration

Section: 9.5

Difficulty Level: Easy

43. What is the expected major product for the following reaction?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: B

Topic: Oxymercuration-Demercuration

Section: 9.5

Difficulty Level: Moderate

44. When an alkene is subjected to treatment with Hg(OAc)2 in alcohol, followed by reaction with NaBH4, what functional group is formed?

A) ether

B) epoxide

C) alkane

D) syn diol

E) alkyne

Ans: A

Topic: Hydroboration-Oxidation

Section: 9.6

Difficulty Level: Easy

45. The regioselectivity and stereospecificity in the hydroboration-oxidation of an alkene is best described as:

A) Markovnikov orientation with syn-addition

B) Markovnikov orientation with anti-addition

C) Anti-Markovnikov orientation with syn-addition

D) Anti-Markovnikov orientation with anti-addition

E) Markovnikov orientation with both syn- and anti-addition

Ans: C

Topic: Hydroboration-Oxidation

Section: 9.6

Difficulty Level: Easy

46. What reagents are needed to accomplish the following transformation?

[pic]

A) H2O/H+

B) H2O/Peroxide

C) OH–

D) BH3

E) 1. BH3, 2. HO–, H2O2, H2O

Ans: E

Topic: Hydroboration-Oxidation

Section: 9.6

Difficulty Level: Easy

47. What is the expected major product for the following reaction sequence?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: E

Topic: Hydroboration-Oxidation

Section: 9.6

Difficulty Level: Easy

48. What is the expected major product for the following reaction sequence?

[pic]

A) I

B) II

C) III

D) I and II

E) I and III

Ans: E

Topic: Hydroboration-Oxidation

Section: 9.6

Difficulty Level: Moderate

49. What is the expected major product for the following reaction sequence?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: E

Topic: Hydroboration-Oxidation

Section: 9.6

Difficulty Level: Moderate

50. What is the expected major product for the following reaction sequence?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: D

Topic: Hydroboration-Oxidation

Section: 9.6

Difficulty Level: Moderate

51. What is the expected major product for the following reaction sequence?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: B

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

52. What is the expected major product for the hydrogenation of an alkene?

A) dihaloalkane

B) alkane

C) haloalkane

D) alcohol

E) ether

Ans: B

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

53. Provide the major organic product(s) for the reaction shown below.

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: B

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

54. What product is formed when 5-chloro-1-methylcyclohexene is reduced with a Pt catalyst and H2?

A) 1-chloro-5-methylcyclohexane

B) 1-chloro-3-methylcyclohexane

C) 5-chloro-1-methylcyclohexane

D) 3-chloro-1-methylcyclohexane

E) None of the above

Ans: B

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

55. What product is formed when trans-1,2-dimethylcyclohexane is reacted with Pd/C and H2?

A) No reaction

B) cis-1,2-dimethylcyclohexane

C) trans-3,4-dimethylhexane

D) trans-1,2-dimethylhexane

E) None of the above

Ans: A

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

56. Which of the following reagents accomplishes the transformation shown below?

[pic]

A) H2/HCl

B) H2/H2SO4

C) H2/Ni

D) H2O/Ni

E) H2O/H2SO4

Ans: C

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

57. Which of the reagents below are expected to convert cyclopentene into cyclopentane?

A) H2 and Ni

B) H2O

C) Heat

D) Zn, H3O+

E) Light

Ans: A

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

58. Which alkene would yield 3-methylpentane upon subjection to catalytic hydrogenation?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: B

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

59. How many moles of hydrogen (H2) are consumed in the catalytic reduction of 1 mole of 1,3-dibromocyclohexa-1,4-diene?

A) 12

B) 2

C) 3

D) 4

E) None of the above

Ans: B

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

60. How many moles of hydrogen (H2) are required to completely reduce 1 mole of cis-2,3,3-trimethylhepta-1,5-diene?

A) 02

B) 1

C) 2

D) 3

E) 4

Ans: C

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

61. Which of the catalysts listed are used in the homogenous catalytic hydrogenation of alkenes?

I) Ni II) Pt III) Wilkinson

A) I

B) II

C) III

D) I and II

E) II and III

Ans: C

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

62. In conducting a catalytic hydrogenation of an alkene, which catalyst listed is most likely soluble in the reaction medium?

A) Ni

B) Pt

C) Pd

D) Wilkinson

E) All of the above are soluble

Ans: D

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

63. Wilkinson’s catalyst accomplishes which of the listed molecular transformations?

A) syn addition of H2 to an alkene

B) anti addition of H2 to an alkene

C) syn dihydroxylation of an alkene

D) anti dihydroxylation of an alkene

E) oxidative cleavage of an alkene

Ans: A

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Easy

64. For the catalytic hydrogenation of alkenes, select from below those most likely to function as a homogenous catalyst?

A) Wilkinson

B) Ni

C) Pd

D) Pt

E) Au

Ans: A

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Moderate

65. Which of the following will yield 2-methylpentane upon catalytic hydrogenation?

A) 2-methyl-1-pentene2

B) 2-methyl-2-pentene

C) 4-methyl-2-pentene

D) 4-methyl-1-pentene

E) All of the above

Ans: E

Topic: Catalytic Hydrogenation

Section: 9.7

Difficulty Level: Moderate

66. For the complete reduction of 1 mole of (3E,5E)-hepta-1,3,5-triene with H2 using a Pd catalyst, how many moles of H2 are consumed?

A) 1

B) 2

C) 3

D) 4

E) 5

Ans: C

Topic: Catalytic Hydrogenation and Stereospecificity

Section: 9.7

Difficulty Level: Moderate

67. What products are produced from the reaction below?

[pic]

A) I, II, III

B) II, III, IV

C) I and IV

D) II and III

E) I, II, III, and IV

Ans: A

Topic: Catalytic Hydrogenation and Stereospecificity

Section: 9.7

Difficulty Level: Moderate

68. Identify the major organic product generated from the reaction shown.

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: B

Topic: Halogenation

Section: 9.8

Difficulty Level: Easy

69. Which reaction intermediate is formed when 4-methylcyclohexene reacts with Br2 dissolved in CCl4?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: B

Topic: Halogenation

Section: 9.8

Difficulty Level: Easy

70. What is the expected major product upon reaction of 1-pentene with Cl2?

A) 1-chloropentane

B) 2-chloropentane

C) 1,1-dichloropentane

D) 2,2-dichloropentane

E) 1,2-dichloropentane

Ans: E

Topic: Halogenation and Stereospecificity

Section: 9.8

Difficulty Level: Easy

71. Treating 2-methyl-2-pentene with Br2 is expected to produce which of the following as the major product?

A) 2,3-dibromo-2-methylpentane

B) 2,2-dibromo-2-methylpentane

C) 3,3-dibromo-2-methylpentane

D) 2-bromo-2-methylpentane

E) 3-dibromo-2-methylpentane

Ans: A

Topic: Halohydrin Formation

Section: 9.8

Difficulty Level: Easy

72. The expected intermediate formed during a halohydrin reaction is:

A) a halonium ion.

B) the most stable carbocation with OH on the adjacent carbon.

C) the most stable carbocation with X on the adjacent carbon.

D) a cyclic oxonium ion.

E) the most stable carbanion.

Ans: A

Topic: Halohydrin Formation

Section: 9.8

Difficulty Level: Easy

73. What major product is expected from the following reaction?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: D

Topic: Halohydrin Formation

Section: 9.8

Difficulty Level: Moderate

74. What is the expected major product for the following reaction?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: D

Topic: Halogenation and Stereospecificity

Section: 9.8

Difficulty Level: Moderate

75. Which of the statements is most correct regarding the products expected from the halogenation reaction shown below?

[pic]

A) Equal amounts of I and II are produced.

B) Equal amounts of III and IV are produced.

C) Equal amounts of I and IV are produced.

D) Equal amounts of II and III are produced.

E) Equal amounts of I and III are produced.

Ans: B

Topic: Halogenation and Stereospecificity

Section: 9.8

Difficulty Level: Moderate

76. For the halogenation reaction shown below, which of the following statements is correct regarding the expected products?

[pic]

A) Equal amounts of I and II produced

B) Equal amounts of III and IV produced

C) Equal amounts of I and IV produced

D) Equal amounts of II and III produced

E) Equal amounts of I and III produced

Ans: A

Topic: Halogenation, Regioselectivity, and Stereospecificity

Section: 9.8

Difficulty Level: Hard

77. The reaction of Br2 with 1-methylcyclohexene, in the presence of ethylamine (EtNH2), is expected to produce which of the following as the major product?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: D

Topic: anti dihydroxylation

Section: 9.9

Difficulty Level: Easy

78. For the reaction sequence below, identify the expected major products.

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: B

Topic: anti dihydroxylation

Section: 9.9

Difficulty Level: Moderate

79. For the reaction sequence below, identify the expected major product(s).

[pic]

A) I

B) II

C) III

D) I and III

E) II and III

Ans: D

Topic: anti dihydroxylation

Section: 9.9

Difficulty Level: Moderate

80. What are the major products for the following reaction sequence?

[pic]

A) I and II

B) II and III

C) III and IV

D) I and III

E) II and IV

Ans: E

Topic: anti dihydroxylation

Section: 9.9

Difficulty Level: Moderate

81. What is the major product for the following reaction sequence?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: D

Topic: anti dihydroxylation

Section: 9.9

Difficulty Level: Hard

82. For the following dihydroxylation reaction which of the following statements is correct regarding the expected products?

[pic]

A) Equal amounts of I and II produced

B) Equal amounts of III and IV produced

C) Equal amounts of I and IV produced

D) Equal amounts of II and III produced

E) Equal amounts of I and III produced

Ans: E

Topic: anti dihydroxylation

Section: 9.9

Difficulty Level: Hard

83. An unknown alkene was reacted with MCPBA in dichloromethane, followed by work-up with H2O/H+. A racemic mixture of the compound shown below was obtained. What is correct name of the starting alkene?

[pic]

A) (Z)-3-methylpent-2-ene

B) (E)-3-methylpent-2-ene

C) 2-methylpent-2-ene

D) 2,3-dimethylbut-2-ene

E) none of the above

Ans: A

Topic: syn Dihydroxylation

Section: 9.10

Difficulty Level: Easy

84. Identify the expected major organic product resulting from the following reaction sequence.

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: A

Topic: syn Dihydroxylation

Section: 9.10

Difficulty Level: Easy

85. Treatment of 1,2-dimethylcyclopentene with OsO4, followed by aqueous NaHSO3, produces which of the following:

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: A

Topic: syn Dihydroxylation

Section: 9.10

Difficulty Level: Easy

86. Identify the expected major organic product generated from the reaction sequence shown.

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: B

Topic: syn Dihydroxylation

Section: 9.10

Difficulty Level: Easy

87. Which of the following alkene addition reactions occur(s) specifically in syn fashion?

A) dihydroxylation using OsO4, H2O2

B) addition of H2

C) hydroboration

D) addition of HCl

E) A, B, and C

Ans: E

Topic: syn Dihydroxylation

Section: 9.10

Difficulty Level: Easy

88. What is the expected major product for the following reaction sequence?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) None of the above

Ans: A

Topic: Oxidative Cleavage

Section: 9.11

Difficulty Level: Easy

89. Provide the expected major organic product of the reaction sequence shown.

[pic]

A) I and II

B) IV and V

C) I only

D) II only

E) III only

Ans: E

Topic: Oxidative Cleavage

Section: 9.11

Difficulty Level: Easy

90. Which of the following reagents effectively cleaves a carbon-carbon double bond?

A) Cl2/hυ

B) [pic]

C) H2SO4

D) cold KMnO4

E) O3/DMS

Ans: E

Topic: Oxidative Cleavage

Section: 9.11

Difficulty Level: Moderate

91. How many carbonyls are generated upon treatment of the molecule below with ozone, followed by zinc metal and water?

[pic]

A) 1

B) 2

C) 3

D) 4

E) 8

Ans: E

Topic: Oxidative Cleavage

Section: 9.11

Difficulty Level: Moderate

92. Of the alkenes shown, which would produce the product shown below, upon treatment with ozone, followed by zinc metal and water?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: B

Topic: Oxidative Cleavage

Section: 9.11

Difficulty Level: Moderate

93. What is the expected major product of the reaction sequence shown below?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: A

Topic: Oxidative Cleavage

Section: 9.11

Difficulty Level: Moderate

94. What are the expected major products from the reaction sequence shown below?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: A

Topic: Predicting Addition Products

Section: 9.12

Difficulty Level: Easy

95. Which of the following alkene addition reactions occur(s) specifically in an anti fashion?

A) hydroboration-oxidation

B) addition of Br2

C) addition of H2

D) addition of H2O in dilute acid

E) both A and B

Ans: B

Topic: Predicting Addition Products

Section: 9.12

Difficulty Level: Easy

96. The Markovnikov product, resulting from an addition reaction to an unsymmetrical alkene, is formed because:

A) the product is statistically favored.

B) steric hindrance favors its formation.

C) the reaction proceeds via the more/most stable carbocation.

D) the reaction forms the more/most stable product.

E) All of the above are valid reasons

Ans: C

Topic: Predicting Addition Products

Section: 9.12

Difficulty Level: Easy

97. What is the expected major product for the following reaction sequence?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: A

Topic: Predicting Addition Products

Section: 9.12

Difficulty Level: Easy

98. What reagents are most likely to accomplish the transformation shown below?

[pic]

A) 1. BH3 / 2. HO–, H2O2, H2O

B) H+, H2O

C) 1. Hg(OAc)2, H2O, THF / 2. NaBH4

D) 1. Hg(OAc)2, CH3OH / 2. NaBH4

E) NaOH, H2O

Ans: A

Topic: Predicting Addition Products

Section: 9.12

Difficulty Level: Easy

99. Which reaction is not stereospecific?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: C

Topic: Predicting Addition Products

Section: 9.12

Difficulty Level: Moderate

100. The expected product(s) resulting from addition of Br2 to (E)-3-hexene would be:

A) a meso dibromide.

B) a mixture of optically active enantiomeric dibromides.

C) a mixture of optically inactive enantiomeric dibromides.

D) (Z)-3,4-dibromo-3-hexene.

E) (E)-3,4-dibromo-3-hexene.

Ans: A

Topic: Predicting Addition Products

Section: 9.12

Difficulty Level: Moderate

101. Which of the following alkenes will yield a meso dihalide when reacted with Br2/CCl4 at room temperature?

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) Both B and D

Ans: B

Topic: Predicting Addition Products

Section: 9.12

Difficulty Level: Moderate

102. What is the expected major product resulting from the acid-catalyzed hydration of 2,5-dimethyl-2-hexene?

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: B

Topic: Predicting Addition Products

Section: 9.12

Difficulty Level: Hard

103. What is the expected major product resulting from treatment of (E)-3-methyl-3-hexene with Br2 in the presence of methanol, CH3OH?

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) All of the above are produced in equal amounts

Ans: A

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Easy

104. To accomplish a Markovnikov addition of water to an unsymmetrical alkene, with minimal skeletal rearrangement, the best reagents would be:

A) water and dilute acid

B) water and concentrated acid

C) 1. Hg(OAc)2, H2O 2. NaBH4, NaOH

D) 1. BH3•THF 2. H2O2, NaOH

E) 1. OsO4, pyridine 2. NaHSO3, H2O

Ans: C

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Easy

105. For the reaction sequence shown, what is the expected major elimination product?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: B

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Easy

106. For the reaction sequence shown, what is the expected major elimination product?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: D

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Easy

107. What is the expected major product of the following reaction sequence?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: C

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Moderate

108. What is the expected major product of the following reaction sequence?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: A

Topic: Synthetic Strategies, anti Dihydroxylation

Section: 9.13, 9.9

Difficulty Level: Moderate

109. Which is the correct sequence of reaction steps necessary to complete the following transformation?

[pic]

A) I then II then III

B) II then I then III

C) II then IV

D) III then I

E) I then IV then II then III

Ans: B

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Moderate

110. What is the expected major product of the following reaction sequence?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: C

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Moderate

111. What is the expected major product of the following reaction sequence?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: A

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Moderate

112. What is the expected major product for the following reaction?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: A

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Moderate

113. What is the expected major product of the following reaction sequence?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: C

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Moderate

114. What is the expected major product of the following reaction sequence?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: A

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Hard

115. What is the expected major product of the following reaction sequence?

[pic]

A) I

B) II

C) III

D) IV

E) V

Ans: C

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Hard

116. For the following reaction sequence, which molecule is an expected major product?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: A

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Hard

117. What is the expected major product of the following reaction sequence?

[pic]

A) [pic]

B) [pic]

C) [pic]

D) [pic]

E) [pic]

Ans: E

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Hard

118. For the following reaction sequence identify the expected major organic products and provide their stereochemical relationship.

[pic]

A) I and II; enantiomers

B) III and IV; enantiomers

C) I and II; diastereomers

D) II and III; diastereomers

E) III and IV; diastereomers

Ans: D

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Hard

119. For the following reaction sequence identify the total number, frequency and types of stereoisomeric compounds expected as products.

[pic]

A) 2 total stereoisomers; 1 set of enantiomers

B) 4 total stereoisomers; 2 sets of enantiomers

C) 4 total stereoisomers; 4 diastereoisomers

D) 8 total stereoisomers; 4 sets of enantiomers

E) 8 total stereoisomers; 8 diastereomers

Ans: E

Short Answer Questions:

Topic: Introduction to Addition Reactions

Section: 9.1

Difficulty Level: Easy

120. π bonds are quite susceptible to reaction with electron-seeking reagents, also referred to as ____________________.

Ans: electrophiles

Topic: Regioselectivity

Section: 9.3

Difficulty Level: Easy

121. The rule that correctly predicts the regiochemistry of most ionic additions to alkenes is called ____________________.

Ans: Markovnikov's Rule

Topic: Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

122. For the following reaction sequence provide the expected major organic product(s). Include all stereoisomers showing relevant stereochemistry.

[pic]

Ans:

[pic]

Topic: Hydrohalogenation

Section: 9.3

Difficulty Level: Easy

123. Provide the structure(s) of the expected major organic product(s) generated upon completion of the following reaction scheme:

[pic]

Ans: [pic]

Topic: Hydrohalogenation and Carbocation Rearrangements

Section: 9.3

Difficulty Level: Moderate

124. The reaction of HCl with 2-ethyl-1-pentene or HCl with 3-methyl-2-hexene results in the identical major product of 3-chloro-3-methylhexane. Provide a mechanistic scheme showing the reaction of each alkene with HCl, including the intermediate and product. Provide a brief explanation how the different alkene reactants were transformed into the same product.

Ans:

[pic]

Electrophilic addition of a proton in the reaction between HCl and both alkenes will result in formation of the most stable intermediate carbocation. Addition of Cl– to the tertiary carbocation formed in both cases results in the observed product. The reason for the identical major product is a consequence of regioselective addition to the double bond forming the same tertiary carbocation intermediate.

Topic: Hydrohalogenation and Carbocation Rearrangements

Section: 9.3

Difficulty Level: Moderate

125. When the two constitutional isomers, 3,3-dimethyl-1-butene and 2,3-dimethyl-2-butene, are reacted with HCl the same major product is formed. Provide a mechanistic explanation for the observation.

Ans: [pic]

For the unsymmetrical 3,3-dimethyl-1-butene, the carbocation formed is 2°, but can readily undergo a methyl shift to form the more stable 3° carbocation, which is the same as that formed from 2,3-dimethyl-2-butene. The addition of the chloride ion to the carbocation forms the identical product, 2-chloro-2,3-dimethylbutane.

Topic: Hydrohalogenation and Carbocation Rearrangements

Section: 9.3

Difficulty Level: Moderate

126. Addition of HI to the alkene of the cyclobutane in the scheme below, results in a significant yield of the product shown. What other product(s) might also be obtained? Explain with a mechanism and brief discussion the observation of the given product as well as others that may arise.

[pic]

Ans: [pic]

Regioselective addition of the proton of HI generates a secondary carbocation. Rearrangement to a more stable 3o carbocation can occur by two alternative pathways (1 and 2). Pathway 1 results in relief of ring strain by expansion to a more stable 5-membered ring. The second pathway involving a methyl shift is less likely; ring strain is not relieved and becomes worse with incorporation of an sp2 carbon (bond angle 120°) into the cyclobutane (bond angle 90°). The third pathway occurs if addition of iodide to occurs before carbocation rearrangement. The first pathway is most likely, resulting in the observed product.

Topic: Acid-Catalyzed Hydration

Section: 9.4

Difficulty Level: Easy

127. For the following reaction sequence provide the expected major organic product(s). Include all stereoisomers showing relevant stereochemistry.

[pic]

Ans:

[pic]

Topic: Acid-Catalyzed Hydration

Section: 9.4

Difficulty Level: Easy

128. For the following reaction sequence provide the expected major organic product(s). Include all stereoisomers and clearly show relevant stereochemistry.

[pic]

Ans:

[pic]

Topic: Acid Catalyzed Hydration

Section: 9.4

Difficulty Level: Easy

129. Provide the structure(s) of the expected major organic product(s) generated upon completion of the following reaction scheme:

[pic]

Ans:

[pic]

Topic: Acid-Catalyzed Hydration

Section: 9.4

Difficulty Level: Moderate

130. The transformation shown below generates an achiral product from a chiral starting material. Provide the structure of the expected product and a mechanism explaining the transformation. Briefly explain why the product formed is achiral.

[pic]

Ans:

[pic]

[pic]

Upon addition of the proton to the alkene a 2° carbocation is formed that undergoes a hydride shift to form a more stable 3° carbocation. The 3° carbocation is located in the center of the chain, and being sp2 hybridized is planar. Addition of water to the central carbon produces a product with no stereocenter and is thus achiral.

Topic: Hydroboration-Oxidation

Section: 9.6

Difficulty Level: Easy

131. A reaction that could potentially yield two or more constitutional isomers, but as in hydroboration-oxidation produces only one isomer, is said to be _____________________.

Ans: regioselective

Topic: Hydroboration-Oxidation

Section: 9.6

Difficulty Level: Easy

132. Any proper mechanism of hydroboration-oxidation must explain the observed _________ addition of the H and OH to the alkene as well as the _____________ regiochemistry.

Ans: syn, anti-Markovnikov

Topic: Hydroboration-Oxidation

Section: 9.6

Difficulty Level: Easy

133. Provide the structure(s) of the expected major organic product(s) generated upon completion of the following reaction scheme:

[pic]

Ans: [pic]

Topic: Halohydrin Formation

Section: 9.8

Difficulty Level: Easy

134. Provide the expected major organic product from the reaction shown below. Provide a brief explanation of any regioselectivity the reaction is expected to produce.

[pic]

Ans: [pic]

The alcohol will be found at the tertiary carbon, being the more substituted carbon. Initial formation of the bromonium ion will favor attack of the water at the more substituted carbon which is more capable of stabilizing the partial positive charge that develops in the transition state.

Topic: Halohydrin Formation

Section: 9.8

Difficulty Level: Moderate

135. For the following transformation below, provide a detailed step-wise mechanism showing the electron flow using the curved arrow formalism.

[pic]

Ans:

[pic]

Topic: Halohydrin Formation

Section: 9.8

Difficulty Level: Moderate

136. For the following reaction draw out the expected major organic product(s). Include regiochemical and/or stereochemical details as relevant, and provide a short justification for the product(s) drawn.

[pic]

Ans: [pic]

The reaction takes place with Markovnikov regioselectivity and anti stereospecificity, giving a racemic mixture of the halohydrin as the major product.

Topic: Halogenation and Stereospecificity

Section: 9.8

Difficulty Level: Moderate

137. Draw Fischer projection formulas of the major product of the reaction between (E)-2-methyl-3-hexene and aqueous Br2.

Ans: [pic]

The reaction takes place with anti stereospecificity. Since the alkene is symmetrically substituted, Markovnikov rule is not applicable, and the reaction is not regioselective. The product mixture would therefore consist of 2 pairs of enantiomers, which are constitutional isomers of each other.

Topic: Oxidative Cleavage

Section: 9.11

Difficulty Level: Easy

138. Provide the structure(s) of the expected major organic product(s) generated upon completion of the following reaction scheme:

[pic]

Ans:

[pic] and [pic]

Topic: Predicting Reaction Products: Halohydrin Formation and Stereospecificity

Section: 9.12

Difficulty Level: Moderate

139. Predict the structure(s) of the expected major organic product(s) of the following reaction. Include regiochemical and/or stereochemical details as needed.

[pic]

Ans: [pic]

The reaction takes place with Markovnikov regioselectivity and anti stereospecificity. As the product is chiral, the products are diastereomers.

Topic: Predicting Reaction Products: syn Dihydroxylation

Section: 9.12

Difficulty Level: Moderate

140. Draw Fischer projection formula(s) of the major product(s) of the reaction between (Z)-2-methyl-3-hexene and cold, alkaline KMnO4.

Ans: [pic]

The reaction takes place with syn stereospecificity, giving a racemic mixture of the diol product.

Topic: Predicting Reaction Products: syn Dihydroxylation

Section: 9.12

Difficulty Level: Moderate

141. Draw Fischer projection formula(s) of the major product(s) of the reaction between (Z)-3-methyl-3-hexene and catalytic OsO4 NMO.

Ans: [pic]

The reaction takes place with syn stereospecificity, giving a racemic mixture of the diol product.

Topic: Predicting Reaction Products: anti Dihydroxylation

Section: 9.12

Difficulty Level: Moderate

142. Draw Fischer projection formula(s) of the major product(s) of the reaction between (Z)-3-methyl-3-hexene and MCPBA, followed by acidic water.

Ans: [pic]

The reaction takes place with anti stereospecificity, giving a racemic mixture of the diol product.

Topic: Predicting Reaction Products: Oxidative Cleavage

Section: 9.12

Difficulty Level: Moderate

143. Predict the product(s) of the oxidation of 2,3,4-trimethyl-1,5-heptadiene upon treatment with O3 followed by dimethylsulfide (DMS).

Ans: [pic]

Topic: Synthetic Strategies

Section: 9.14

Difficulty Level: Moderate

144. A common problem in the acid catalyzed hydration of alkenes is the formation of an ether byproduct. Explain the formation of the ether byproduct in relation to the reaction below:

[pic]

Ans: [pic]

Topic: Predicting Reaction Products: Halohydrin Formation and Stereospecificity

Section: 9.12

Difficulty Level: Hard

145. Identify the structure(s) of the expected major organic product(s) of the following reaction. Draw the products in the expected chair conformations and include regiochemical and/or stereochemical details as needed.

[pic]

Ans:

[pic]

The reaction takes place with Markovnikov regioselectivity and anti stereospecificity. The starting material is shown as a single enatiomers, and thus produces two diastereomers. The product containing the cis fused rings is capable of a ring flip.

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Hard

146. Starting with (2R,3R)-2-chloro-3,4-dimethylpentane, a) draw the expected major product for each step, including regiochemical and stereochemical details when needed. In addition, b) briefly explain the mechanistic rational for each transformation.

i. t-BuOK/t-BuOH, heat

ii. MCPBA/CH2Cl2

iii. H3O+

Ans: [pic]

Hofmann elimination occurs upon heating with the bulky potassium tert-butoxide base, through an E2 elimination. Epoxidation with MCPBA is stereospecific (syn), giving a racemic (R,R & S,R) epoxide. Ring opening of the epoxide under acidic conditions is regio- and stereospecific.

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Hard

147. For the following transformation a) identify the starting material with correct stereochemistry and b) provide a complete reaction mechanism, including stereochemistry, to account for the product shown.

[pic]

Ans:

[pic]

Step 1 involves the epoxidation of the (E) alkene by MCPBA, showing only the enantiomer leading given product. Acid catalyzed ring opening of the epoxide would occur with regiospecific addition of MeOH to the 3° carbon. Deprotonation by a general base (likely MeOH in this example) provides the product, which upon ( bond rotation has the same conformation as the product given in the question.

Topic: Synthetic Strategies

Section: 9.13

Difficulty Level: Hard

148. Consider the information given below and identify the structure of the unknown compound A, with a molecular formula of C8H14. Compound A reacts with Br2/CCl4. Upon reaction with excess H2/Ni 1-ethyl-2-methylcyclopentane is produced. Subjecting A to ozonolysis, the product shown below is produced as the major organic product. Draw the correct structure of compound A, and provide a brief and clear explanation relating the data provide with the structure selected.

[pic]

Ans: A must be 3-ethyl-4-methylcyclopentene. This given data can be explained as shown below:

[pic]

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