Ch9-ques-2013

Chapter 9 Multiple Choice Questions: Topic: Addition Reaction Mechanisms Section: 9.1 Difficulty Level: Easy 1. In an addition reaction to an alkene, the 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 bond B) addition of two groups across a double bond C) breaking of a 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 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:

A)

B) C)

D)

Br

Br

E)

Br

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? CH2 CH3 CH3 CH3 CH3

I II III IV V 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?

A)

Br

B) Br

C) Br

D) Br

E)

Br

Ans: B

Topic: Hydrohalogenation Section: 9.3 Difficulty Level: Easy 14. The expected major product of the following reaction is:

HBr?

A) Br

B)

Br

C) Br

D) Br

E) Br

Br

Ans: C

Topic: Hydrohalogenation Section: 9.3 Difficulty Level: Easy 15. The expected major product of the following reaction is:

HBr?

ROOR

A)

Br

B)

C)

Br

D)

Br

E)

Br Br

Ans: A Topic: Hydrohalogenation Section: 9.3 Difficulty Level: Easy 16. What is the expected major product for the following reaction?

Br Br

Br

Br

II III IV VI

HBr?

ROOR

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?

A)

Br

B)

Br

C) Br

D) Br

E) Br 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)

B)

C)

CH3

D)

E) Ans: B

Topic: Stereochemistry of Hydrohalogenation Section: 9.3 Difficulty Level: Easy 19. What is the major product for the following reaction?

HI

A)

I

B) I

C) I

D)

I

I

E)

I

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)

B) C)

D)

E) Ans: B

Topic: Hydrohalogenation Section: 9.3 Difficulty Level: Moderate 21. Which of the given reaction schemes would produce the molecule shown below?

Br

A)

HBrROOR

B)

HBr

C)

HBrROOR

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?

HBr BrH

Br H H Br

I II III IV 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?

H3C H3C

I II III

H2C CH3 CH3 CH3

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? CH3

I II III

CH2 CH2

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:

Br

I II III

Br

Cl

Br

Cl

Br

Cl

Br

Cl

IV V

Br

Cl

?HCl

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:

HBr

A)

Br

B) + enantiomer

Br

C) + enantiomer

Br

Br

D) Br

E)

Br

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?

HCl

A) Cl+ enantiomer

B) Cl+ enantiomer

C) Cl + enantiomer

D)

Cl+ enantiomer

E) Cl+ enantiomer

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:

HBr?

A)

Br

B)

Br

C) Br 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?

HBr

A) Br

+ enantiomer

B) Br

C) Br+ enantiomer

D)

Br+ enantiomer

E)

Br+ enantiomer

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:

H+ ?H2O

OHOH OH

OHOH

II III IV VIOH



OH OH

OH

OH

II III IV VI

H3O+

H2O

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


H3O+ ?

A) OH

OH

B)

OH

OH

C) OH

D) OH

E) OH

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?

II III IV VI

HO HO

HOHO

OH

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?

II III IV VI

Cl

OH

ClCl Cl Cl

OHOH

OH

OH

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?

[H2SO4]MeOH

A) OMe

B) + enantiomer

OMe

C) + enantiomer

OMe

D)

+ enantiomer

OMe

E) + enantiomer

OMe

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?

1. Hg(OAc)2, H2O

2. NaBH4, NaOH

A)

B) + enantiomer

OH

C) + enantiomer

OHHO

D)

HO

E)

HO

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


1. Hg(OAc)2, H2O

2. NaBH4, NaOH

A)

O

HO

B)

+ enantiomer

OH

C)

OH

D)

+ enantiomer

OH

E) + enantiomer

OHOH

Ans: C


1. Hg(OAc)2, H2O

2. NaBH4, NaOH

A) + enantiomer

OH

B)

+ enantiomerOH

OH

C) + enantiomer

OH

D) + enantiomer

HO

E) + enantiomer

OH

Ans: D


1. Hg(OAc)2, EtOH

2. NaBH4, NaOH

A) O

B)

O

C) O

D) O

HO + CO2

E) OH 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?

CH3 ? CH3

OH !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?

1. BH3THF

2. H2O2, NaOH

A) + enantiomer

OH

B)

C) OH

D) +

O

H

O

H H

E)

OH

Ans: E

Topic: Hydroboration-Oxidation Section: 9.6 Difficulty Level: Easy 48. What is the expected major product for the following reaction sequence?

+enantiomer

OHOH

OH

+enantiomer

+enantiomer

1. BH3THF

2. H2O2, NaOH

II IIII 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?

1. BH3THF

2. H2O2, NaOH

A)

+ enantiomerOH

OH

B) H

O

O

C)

+ enantiomer

OH

D) OH

E)

+ enantiomer

OH Ans: E


1. BD3THF

2. H2O2, NaOH

OH D DHO OHD D+

enantiomer+

enantiomer+

enantiomer+

enantiomer+

enantiomer

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


1. BH3THF

2. H2O2, NaOH

A) HO

B) + enantiomer

HO

C) + enantiomer

HO

D) + enantiomerOH

E) HO

HO

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.

?H2, Pd/C

!

A)

Pd

B)

C) OHOH

D)

E) 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?

?

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?

I II III IV V 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. Wilkinsons 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?

II III IVI

?H2Pt

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.!

I II III

DDCH3D

DCH3

DDCH3

IV

CH3

DH

V

CH3D

+enantiomer

+enantiomer

+enantiomer

+enantiomer

+enantiomer

?D2Pd

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?

II III IVI V

Br

H3C H3CBr

H3C

Br

Br Br

Br


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?

Br2 ?H2O

II III IV VI

Br

OH Br

OH

Br OH Br

OH Br Br


Topic: Halohydrin Formation Section: 9.8 Difficulty Level: Moderate 74. What is the expected major product for the following reaction?

Br2, CH3OH

OH

Br

H3CO

Br

Br

OCH3

OCH3

Br

I II III IV V

+enantiomer

+enantiomer

+enantiomer

+enantiomer

BrH3CO

?


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?

Br2, CCl4

I

CH3BrBr

C2H5

HH

CH3BrBr

C2H5

HH

II

CH3BrH

C2H5

HBr

III

C2H5BrH

CH3

HBr

IV

?

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?

I2, CCl4

I II III

C2H5II

C2H5

H3CH

C2H5IH

C2H5

H3CI

C2H5II

C2H5

CH3H

IV

C2H5ICH3

C2H5

HI

?

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?

I II III IV V

+enantiomer

+enantiomer

+enantiomer

+enantiomer

CH3

NHEtBr

CH3

BrNHEt

CH3

NHEtBr

CH3

BrNHEt

NHEtBr


Topic: anti dihydroxylation Section: 9.9 Difficulty Level: Easy 78. For the reaction sequence below, identify the expected major products.

1. MCPBA2. H3O+

?

A) + enantiomer

O

B) + enantiomer

OH

OH

C)

+ enantiomerHO

OH

D) + enantiomer

OH

OH

E) + enantiomer

OH

OH Ans: B

Topic: anti dihydroxylation Section: 9.9 Difficulty Level: Moderate 79. For the reaction sequence below, identify the expected major product(s).

1. MCPBA2. H+, H2O

?

HO

OHH

HH3CH2C CH2CH3

HO

OHH H

H3CH2C

CH2CH3HO

OHH

H

H3CH2CCH2CH3

II IIII 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?

CH3

I II III IV

1. MCPBA2. H3O+

?

OH

CH3OH

CH3

OHOH

CH3

OHOH

OH

CH3OH

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?

1. MCPBA

OH

OCH3

H3COOH

OH

OCH3

OCH3

OH

I II III IV V

+enantiomer

+enantiomer

+enantiomer

+enantiomer

+enantiomer

OCH3

OCH3

2. [H2SO4], CH3OH?

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?

I II III

CH(CH3)2OHOH

CH2CH3

H3CH2CH

CH(CH3)2CH2CH3H

CH2CH3

HOHO

CH(CH3)2H3CH2C

HOCH2CH3

OHH

IV

CH2CH3OHCH2CH3

CH(CH3)2

HHO

1. MCPBA2. H3O+

?

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?

+ enantiomerOH

OH 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.

?1. KMnO4, NaOH

Cold

OH

OH

OH

OH

O

O

OHOH O

O

O

HH

I II III IV V 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:

CH3

II III IV VIOH

OH

CH3CH3

CH3

OH

OHCH3

CH3

OH

HH

CH3

CH3

OHH

CH3

CH3

H

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.!

I II III

OHOHCH3OH

OHCH3

OHOHCH3

IV

CH3

OHH

V

CH2OHOH

+enantiomer

+enantiomer

+enantiomer

+enantiomer

+enantiomer

?1) OsO4

2) NaHSO3/H2O


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?

1. OsO4, pyridine

2. H2O, NaHSO3

A)

+ enantiomerOH

OH

B)

+ enantiomerOH

OH

C)

H

O H

O+

D)

OH

O HO

O+

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.

1. O32. (CH3)2S, (DMS)

?

I II III IV V

O O O O O

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/h

B)

O

O O HR 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?

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?

C C C

OC C C C

O

HHH

HH

HH

HHH

HH

I II III IV V

CH3 CH3 CH3

?


Topic: Oxidative Cleavage Section: 9.11 Difficulty Level: Moderate

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

CH3 1. O32. Zn/H2O

?

H3C

O

H3C

O

H

O

H

O CH3

H

O

H

O

H

O

OH

OCH3

OO

I II III IV V 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?

1. O3

2. Zn/H2O

I II III IV V

O O O OCO2H

+ + + + +OC HH

C OOH

O

H H

O

OH HO

O

OH

?


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?

1. BH3THF

2. H2O2, NaOH

A) OH

B) + CO2

O

OH

C)

D) + enantiomer

OH

E) + enantiomerOH

OH

Ans: A Topic: Predicting Addition Products Section: 9.12 Difficulty Level: Easy 98. What reagents are most likely to accomplish the transformation shown below?

? OH

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?

I

II

III

IV

V

Br2/CCl4trans-2-Butene

cis-2-Pentene

trans-2-Hexene

KMnO4, NaOH2-Methyl-2-heptene

1-Methylcyclohexene D2/Pd

Br2/H2O

HBr

Cold 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)

B)

C) D) 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) HO

B) HO

C)

OH

D) OH

E) HO

OH

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)

Br

OMe

B)

Br

MeO

C)

OMe

Br

D)

OMe

Br 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. BH3THF 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?

1. HI2. NaOMe, MeOH

O

I II III IV V

IO


Topic: Synthetic Strategies Section: 9.13 Difficulty Level: Easy 106. For the reaction sequence shown, what is the expected major elimination product?

1. HBr

2. NaOMe, MeOH

I II III IV V


Topic: Synthetic Strategies Section: 9.13 Difficulty Level: Easy 107. What is the expected major product of the following reaction sequence?

1. HCl

2. t-BuOK, t-BuOH

O

I II III IV V


Topic: Synthetic Strategies Section: 9.13 Difficulty Level: Moderate 108. What is the expected major product of the following reaction sequence?

1. NaOEt, HOEt, heat

2a. Hg(OAc)2, CH3OH2b. NaBH4, NaOH

Br

OCH3 OH

OCH3 OH

OH3C

I II III IV V


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? Br OH

OH+ enantiomer

?

I. MCPBA II. NaOCH2CH3, CH3CH2OH III. H3O+ or -OH IV. 1) OsO4 then 2) NaHSO3/H2O

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


1. NaOEt, EtOH, heat

2a. BH3THF2b. H2O2, NaOH

Cl

HO OH OH+

enantiomer+

enantiomer+

enantiomer

OHHO

HO

OH+

enantiomerI II III IV V



1. NaOEt, EtOH, 70 C

2a. O3, CH2Cl2, -78 C2b. DMS

Br

H

A)

O

O

B) OH

OH

C)

O

O

D)

CH

HC

O

O

E)

OO

H

Ans: A

Topic: Synthetic Strategies Section: 9.13 Difficulty Level: Moderate 112. What is the expected major product for the following reaction?

1. OsO4, pyridine

2. H2O, NaHSO3

A)

+ enantiomerOH

OH

B)

+ enantiomerOH

OH

C)

+ enantiomerOH

OH

D)

H

O H

O+

E)

+ enantiomerOH

OH

OH

Ans: A


1. t-BuOK

2. KMnO4, NaOH, coldCl

A) O OH

O+

B)

+ CO2OH

O

C)

+ enantiomerOHOH

D)

+ enantiomer

OH

OH

E)

+ enantiomer

OH Ans: C


1. t-BuOK, t-BuOH

2a. O3, CH2Cl22b. Me2S

Cl

A) +

O

H H

O

B)

H

O

O

C)

OHOH

D) + enantiomerOH

OH

E)

O

H

O

HHO+

Ans: A

Topic: Synthetic Strategies Section: 9.13 Difficulty Level: Hard 115. What is the expected major product of the following reaction sequence?

1. t-BuOK, t-BuOH

2. HBr

Cl

Br BrBr

Br

Br Cl

I II III IV V


Topic: Synthetic Strategies Section: 9.13 Difficulty Level: Hard 116. For the following reaction sequence, which molecule is an expected major product?

1. t-BuOK2a. OsO4, pyridine2b. H2O, NaHSO3

Br

A)

OHHO

B)

OH

OH

C)

OH

OH

D)

E)

Br

OH

Ans: A Topic: Synthetic Strategies Section: 9.13 Difficulty Level: Hard 117. What is the expected major product of the following reaction sequence?

1. NaOEt, EtOH, 70 C

2a. O3, CH2Cl2, -78 C2b. DMS

BrH

A)

O

O

B) OH

OH

C)

O

O

D)

CH

HC

O

O

E)

OO

H

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.

1. t-BuOK, t-BuOH

2a. BH3THF2b. H2O2, NaOH

I II III IV

OH

HO

Br

OH

HO

OH

HO

OH

HO

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.

Br1. NaOEt, HOEt, heat

2a. Hg(OAc)2, CH3OH2b. NaBH4, NaOH

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. 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.

HI

Ans:

I I

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: HBr

ROOR(CH3)2CHCH2CH CH2?

Ans: Br

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:

Clmost stable carbocation

H Cl

H Cl

Cl

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:

HCl

Cl

HCl

most stable carbocation

3,3-dimethyl-1-butene

2,3-dimethyl-2-butene

Cl

2-chloro-2,3-dimethylbutane

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.

HI I

Ans:

H+ fast I I

II

ring expansion

methyl shift

I

alternative 2

alternative 3I

1,2 addition

alternative 1

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.

H3O+ ?

Ans:

OHOH

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. H3O+ ?

Ans:

HO OH 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: H3O+ ?

Ans:

OH OH

Enantiomers

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.

H3O+ ?H

Ans:

OH

H H+ H

HO H

OH

H:B

O HHydrideshift

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: 1. BH3THF

2. H2O2, NaOHCH3CH2C(CH3)2CH CH2 ?

Ans: OH 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.

Br2 / H2O

Ans:

BrOH

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.

HOBr2 + HBr

O

Br

Ans:

HOBr Br HO Br

O

Br

H

Br + HBrO

Br

!

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.

Br2, H2O ?

Ans: H

Br

OH

HBr

OH+

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:

CH(CH3)2HBr

C2H5

HOH

CH(CH3)2HBr

C2H5

OHH

CH(CH3)2BrH

C2H5

HHO

CH(CH3)2BrH

C2H5

HOH

Br2H2O

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: 1. O32. (CH3)2S, (DMS)

?

Ans:

O

H

and

O

H 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.

?Br2CH3OH

H

Ans: Br OCH3 Br OCH3

H H

+

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:

CH(CH3)2OHOH

C2H5

HH

CH(CH3)2HOHO

C2H5

HH

KMnO4cold, dil

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:

CH2CH3OHOH

C2H5

H3CH

CH2CH3HOHO

C2H5

CH3H

OsO4NMO

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:

CH2CH3CH3OH

C2H5

HOH

CH2CH3H3CHO

C2H5

OHH

1) MCPBA2) H3O+

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:

O O

OH O

OH1) O32) DMS

CO2 H2O

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:

H3O+

H2O OHO

Ans: OH

H+O

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.

H?

Br2CH3OH

Ans:

H

OCH3

Br

H

OCH3Br

H

OCH3Br

HCH3OBrH

H3COBr

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:

Cl

H3C

H

H

MCPBAt-BuOK/t-BuOH(E2: Hofmann elimination) H3C H H3C H

O HO H

(S)-2-((R)-1,2-dimethylmethylpropyl)

oxirane

H3C H

H

(R)-3,4-dimethylpent-1-ene

+CH2Cl2

syn addition(2R,3R)-2-chloro-3,4-

dimethylpentane(R)-2-((R)-

1,2-dimethylmethylpropyl)oxirane

H3O+

H3C H H3C H

HO HOHHO OHH

(2R,3R)-3,4-dimethylpentane-1,2-diol

(2S,3R)-3,4-dimethylpentane-1,2-diol

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.

1) MCPBA2) MeOH, [H2SO4] MeO

OH

?

Ans:

O

OClO

H

O SO

OOHO

HO

H

OHH3C

OH

OH3C HB:

OH

OH3CMeO

OH

Step 1 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.

O O

Ans: A must be 3-ethyl-4-methylcyclopentene. This given data can be

explained as shown below:

O

OOO

Reacts with Br2,CCl4:A must contain a bond

H2, Ni

ozonolysis

C8H14

A must contain thesame carbon skeletonas the product afterhydrogenation, and a bond

The location of the bond position in A is identified from the structure of the ozonolysis product

A

=

Ch9-ques-2013

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b addition reactions

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d addition reactions

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