Ch9-ques-2013 s5b5r

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 ΔS value is negative) observed for alkene addition reactions results from: A) the breaking of a π and σ bond. B) the formation of two σ bonds. C) the reaction being exothermic. D) two molecules reacting to form a single molecule. E) the temperature dependence of the ΔS term. Ans: D


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


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, ΔG, 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 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 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) Br

D)

Br Br

E) Ans:

E


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


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


Which of the structures shown depicts the most stable carbocation intermediate formed in a hydrohalogenation reaction? CH2

I

A) B) C) D) E) Ans:

I II III IV V B

CH3

CH3

CH3

CH3

II

III

IV

V


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

Br

A) Br

B)

C) D)

Br Br Br

E) Ans:

B


The expected major product of the following reaction is: HBr

?

Br

A) Br

B) Br

C)

Br

D) Br

E) Ans:

Br

C


The expected major product of the following reaction is: HBr ROOR Br

?

A) B) Br

C) Br

D) Br

E) Ans:

Br

A


What is the expected major product for the following reaction? HBr ROOR

?

Br Br I

A) B) C) D) E) Ans:

II

I II III IV V D

Br III

Br IV

V

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?

Br

A) Br

B) C)

Br

D) E) Ans:

Br

Br

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) CH3

C) 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

I

A) B)

I

C)

I I

D)

I

I

E) 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 HBr ROOR

A)

HBr

B) HBr

C) D) E) Ans:

ROOR

Both A and B Both B and C 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? Br H Br H

H Br

I

A) B) C) D) E) Ans:

H Br

II

I and II II and III III and IV I and III II and IV E

III

IV

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? H2C CH3

H3C CH3

H3C CH3

I

II

III

A) B) C) D) E) Ans:

I II III I and II II and III D


Which of the following carbocations is likely to undergo rearrangement through a hydride shift? CH2

I

A) B) C) D) E) Ans:

CH3

II

I II III I and II II and III D

CH2

III


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

?

Br Cl

Cl

Cl

Cl Cl

Br

Br

Br

Br

Br

I

II

III

IV

V

A) B) C) D) E) Ans:

I and II II and III I and IV V All of the above are equally likely to form A


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

A)

B)

+ enantiomer

Br

Br

C)

+ enantiomer

Br

Br

D)

Br

E) 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

+ enantiomer

A)

Cl + enantiomer

B)

Cl

Cl

C)

+ enantiomer

Cl + enantiomer

D) + enantiomer

E) Ans:

Cl

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


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

? Br

A) Br

B) C) D) E) Ans:

Br

A and B A and C C


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

+ enantiomer

A) B)

Br

Br

+ enantiomer

C)

Br Br

+ enantiomer

D) Br + enantiomer

E) 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


The expected major product of the following reaction is: H+

?

H2O OH

OH

OH

OH OH I

A) B) C) D) E) Ans:

II

I II III IV V D

III

IV

V

OH


The expected major product of the following reaction is: H3O+ H2O OH OH I

A) B) C) D) E) Ans:

II

OH III

OH IV

I II III IV V C


The expected major product of the following reaction is: H 3O +

?

OH OH

A) OH

B) C) D) E)

OH

OH

OH

OH

V

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?

HO

HO HO

HO I

A) B) C) D) E) Ans:

OH

II

III

IV

V

I and III II III and V IV I, III and V 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? OH OH OH

OH Cl I

A) B) C) D) E) Ans:

Cl

Cl

Cl OH

Cl

II

III

IV

V

I and III II III and V IV I, III and V B

Topic: Acid Catalyzed Hydration Section: 9.4 Difficulty Level: Hard 37.

What is the expected major product for the following reaction? MeOH [H2SO4]

A)

OMe

+ enantiomer

B)

OMe OMe + enantiomer

C) + enantiomer

D)

OMe OMe

+ enantiomer

E) 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


What is the expected major product for the following reaction? 1. Hg(OAc)2, H2O 2. NaBH4, NaOH

A) OH + enantiomer

B) OH HO + enantiomer

C) HO

D) HO

E) Ans:

B


What synthetic goal is achieved by subjecting an alkene to an oxymercurationdemercuration 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


What is the expected major product for the following reaction? 1. Hg(OAc)2, H2O 2. NaBH4, NaOH O H

A)

O

+ enantiomer

B)

OH OH

C) + enantiomer

D)

OH

OH

E) Ans:

OH

C

+ enantiomer


What is the expected major product for the following reaction? 1. Hg(OAc)2, H2O 2. NaBH4, NaOH OH

+ enantiomer

A) OH + enantiomer

B)

OH OH + enantiomer

C) + enantiomer

D)

HO OH

+ enantiomer

E) Ans:

D


What is the expected major product for the following reaction? 1. Hg(OAc)2, EtOH 2. NaBH4, NaOH

A)

O

O

B) C)

O

HO

D)

E) Ans:

+ CO2 O

OH

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


What reagents are needed to accomplish the following transformation? CH3

?

A) H2O/H+ B) H2O/Peroxide C) OH– D) BH3 E) 1. BH3, 2. HO–, H2O2, H2O Ans: E

CH3 OH !


What is the expected major product for the following reaction sequence? 1. BH3•THF 2. H2O2, NaOH

+ enantiomer

A)

OH

B) C)

OH

O

O

+

D)

H

H

H

OH

E) Ans:

E


What is the expected major product for the following reaction sequence? 1. BH3•THF 2. H2O2, NaOH OH OH OH + enantiomer

+ enantiomer

+ enantiomer

I

II

III

A) B) C) D) E) Ans:

I II III I and II I and III E

Topic: Hydroboration-Oxidation Section: 9.6 Difficulty Level: Moderate 49.


OH + enantiomer

A)

OH O H

B)

O

+ enantiomer

C)

OH

D)

OH

+ enantiomer

E) Ans:

OH

E


What is the expected major product for the following reaction sequence? 1. BD3•THF 2. H2O2, NaOH

D

OH + enantiomer I

A) B) C) D) E) Ans:

D

HO

OH

D

+ enantiomer

+ enantiomer

+ enantiomer

II

III

IV

V

I II III IV V D



A)

HO HO + enantiomer

B) HO + enantiomer

C) OH

D) HO

E)

HO

D

+ enantiomer

+ enantiomer

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


Provide the major organic product(s) for the reaction shown below. H2, Pd/C Pd

?!

A) B) OH

C)

OH

D) E) Ans:

B


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


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

A) B) C) D) E) Ans:

H2/HCl H2/H2SO4 H2/Ni H2O/Ni H2O/H2SO4 C


Which of the reagents below are expected to convert cyclopentene into cyclopentane? A) H2 and Ni B) H2 O C) Heat D) Zn, H3O+ E) Light Ans: A


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

I

A) B) C) D) E) Ans:

I II III IV V B

II

III

IV

V


How many moles of hydrogen (H2) are consumed in the catalytic reduction of 1 mole of 1,3-dibromocyclohexa-1,4-diene? A) 1 B) 2 C) 3 D) 4 E) None of the above Ans: B 2


How many moles of hydrogen (H2) are required to completely reduce 1 mole of cis-2,3,3-trimethylhepta-1,5-diene? A) 0 B) 1 C) 2 D) 3 E) 4 Ans: C 2


Which of the catalysts listed are used in the homogenous catalytic hydrogenation of alkenes? I) Ni II) Pt III) Wilkinson A) B) C) D) E) Ans:

I II III I and II II and III C


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


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


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-pentene B) 2-methyl-2-pentene C) 4-methyl-2-pentene D) 4-methyl-1-pentene E) All of the above Ans: E 2

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? H2

?

Pt

I

II

A) B) C) D) E) Ans:

III

IV

I, II, III II, III, IV I and IV II and III I, II, III, and IV A

Topic: Catalytic Hydrogenation and Stereospecificity Section: 9.7 Difficulty Level: Moderate 68.

Identify the major organic product generated from the reaction shown.! D2 Pd D CH3

CH3 D

D

D

+ enantiomer I

A) B) C) D) E) Ans:

+ enantiomer II

I II III IV V B

?

CH3 H

CH3 D D

D

+ enantiomer

+ enantiomer

III

IV

CH3 D

+ enantiomer V

Topic: Halogenation Section: 9.8 Difficulty Level: Easy 69.

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

Br

Br Br H 3C I

A) B) C) D) E) Ans:

H3C

H 3C II

Br III

Br IV

V

I II III IV V 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? Br2

?

H2O OH

Br

Br

I

A) B) C) D) E) Ans:

OH

Br

OH

Br

Br

OH II

I II III IV V D

Br

III

IV

V

Topic: Halohydrin Formation Section: 9.8 Difficulty Level: Moderate 74.

What is the expected major product for the following reaction? Br2, CH3OH

OH

?

Br

OCH3

H3CO Br + enantiomer I

A) B) C) D) E) Ans:

I II III IV V D

Br + enantiomer

OCH3

Br

+ enantiomer

+ enantiomer III

II

H3CO

Br

IV

V

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

CH3 H Br Br H

CH3

C2H5

H Br C2H5

I

II

A) B) C) D) E) Ans:

Br H

H H

? CH3 Br Br

Br Br

CH3 H H

C2H5

C2H5

III

IV

Equal amounts of I and II are produced. Equal amounts of III and IV are produced. Equal amounts of I and IV are produced. Equal amounts of II and III are produced. Equal amounts of I and III are produced. 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

C2H5 I CH3 I H

C2H5 H3C I H I

? C2H5

C2H5 H3C I I H

C2H5

C2H5

C2H5

CH3 I C2H5

I

II

III

IV

A) B) C) D) E) Ans:

I H

Equal amounts of I and II produced Equal amounts of III and IV produced Equal amounts of I and IV produced Equal amounts of II and III produced Equal amounts of I and III produced 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? CH3 Br

CH3 NHEt

NHEt + enantiomer

Br + enantiomer

I

A) B) C) D) E) Ans:

I II III IV V D

II

CH3 Br NHEt + enantiomer III

CH3 NHEt

Br

Br + enantiomer IV

V

NHEt

Topic: anti dihydroxylation Section: 9.9 Difficulty Level: Easy 78.

For the reaction sequence below, identify the expected major products. 1. MBA 2. H3O+

?

O + enantiomer

A) OH + enantiomer

B)

OH

OH + enantiomer

C)

HO OH

D)

+ enantiomer

OH

OH + enantiomer

E) Ans:

OH

B

Topic: anti dihydroxylation Section: 9.9 Difficulty Level: Moderate 79.

For the reaction sequence below, identify the expected major product(s). 1. MBA 2. H+, H2O HO

H3CH2C

H CH2CH3 OH

H

A) B) C) D) E)

I

I II III I and III II and III

H CH2CH3

HO H H3CH2C

OH II

?

CH2CH3 H

HO H H3CH2C

OH III

Ans: D Topic: anti dihydroxylation Section: 9.9 Difficulty Level: Moderate 80.

What are the major products for the following reaction sequence? 1. MBA

CH3

2. H3O+

CH3

CH3 OH OH

OH OH I

A) B) C) D) E) Ans:

?

OH

OH OH CH3

II

III

CH3 OH IV

I and II II and III III and IV I and III II and IV E

Topic: anti dihydroxylation Section: 9.9 Difficulty Level: Moderate 81.

What is the major product for the following reaction sequence? 1. MBA

?

2. [H2SO4], CH3OH OH

OH

OCH3

OCH3

H3CO OCH3

OH

+ enantiomer

+ enantiomer

I

II

A) B) C) D) E)

I II III IV V

OCH3 + enantiomer III

OH + enantiomer IV

OCH3 + enantiomer 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? 1. MBA 2. H3O+ CH(CH3)2 H3CH2C OH H OH

A) B) C) D) E) Ans:

H3CH2C HO

CH(CH3)2 OH H

HO HO

?

CH(CH3)2 CH2CH3 H

CH(CH3)2 HO H

CH2CH3

CH2CH3

CH2CH3

CH2CH3 OH CH2CH3

I

II

III

IV

Equal amounts of I and II produced Equal amounts of III and IV produced Equal amounts of I and IV produced Equal amounts of II and III produced Equal amounts of I and III produced E

Topic: anti dihydroxylation Section: 9.9 Difficulty Level: Hard 83.

An unknown alkene was reacted with MBA 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? OH + enantiomer OH

A) B) C) D) E) Ans:

(Z)-3-methylpent-2-ene (E)-3-methylpent-2-ene 2-methylpent-2-ene 2,3-dimethylbut-2-ene none of the above 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

A) B) C) D) E) Ans:

I

O

OH

OH

I II III IV V A

O OH OH

OH II

?

H H

O

O

O

III

IV

V


Treatment of 1,2-dimethylcyclopentene with OsO4, followed by aqueous NaHSO3, produces which of the following: OH CH3

OH CH3

OH CH3

CH3 H

CH3 H

CH3 OH

OH CH3

H CH3

OH CH3

H CH3

I

A) B) C) D) E) Ans:

II

I II III IV V A

III

IV

V


Identify the expected major organic product generated from the reaction sequence shown.! 1) OsO4 2) NaHSO3/H2O OH CH3

CH3 OH

OH + enantiomer I

A) B) C) D) E) Ans:

OH + enantiomer

I II III IV V B

II

?

CH3 H

CH3 OH OH + enantiomer III

CH2OH OH

OH + enantiomer IV

+ enantiomer V


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


What is the expected major product for the following reaction sequence? 1. OsO4, pyridine 2. H2O, NaHSO3 OH + enantiomer

A)

OH OH + enantiomer

B)

OH H

C)

+

H

O OH

D) E) Ans:

O

O +

O

HO

None of the above A

Topic: Oxidative Cleavage Section: 9.11 Difficulty Level: Easy 89.

Provide the expected major organic product of the reaction sequence shown. 1. O3

?

2. (CH3)2S, (DMS)

O

I

A) B) C) D) E)

O

O II

I and II IV and V I only II only III only

III

O IV

O V

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 O

B) C) D) E) Ans:

R

O

O

H

H2SO4 cold KMnO4 O3/DMS 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) B) C) D) E) Ans:

1 2 3 4 8 E


Of the alkenes shown, which would produce the product shown below, upon treatment with ozone, followed by zinc metal and water? H H HH H O H C C C C H C C C H O H HH H

?

CH3

I

A) B) C) D) E) Ans:

II

CH3

CH3

III

IV

V

I II III IV V B


What is the expected major product of the reaction sequence shown below? CH3

1. O3

?

2. Zn/H2O

O

O

H3C

O H

O

H 3C

O

CH3 H

O

CH3 O

H

O H

O

H

OH

O I

A) B) C) D) E) Ans:

I II III IV V A

II

III

IV

V


What are the expected major products from the reaction sequence shown below? 1. O3

?

2. Zn/H2O O

H

O

+

+

O C

O C O H

A) B) C) D) E) Ans:

II

I II III IV V A

O

+

+

+

O

O

O

H

H

I

O

CO2H

III

OH

H IV

OH

HO V

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


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



OH

A) O

B)

+ CO2

OH

C) D)

OH

E)

OH

+ enantiomer OH

+ enantiomer

Ans: A Topic: Predicting Addition Products Section: 9.12 Difficulty Level: Easy 98.

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

A) B) C) D) E) Ans:

OH

1. BH3 / 2. HO–, H2O2, H2O H+ , H2 O 1. Hg(OAc)2, H2O, THF / 2. NaBH4 1. Hg(OAc)2, CH3OH / 2. NaBH4 NaOH, H2O A


Which reaction is not stereospecific? trans-2-Butene

Br2/CCl4

cis-2-Pentene

Br2/H2O

trans-2-Hexene 1-Methylcyclohexene 2-Methyl-2-heptene

A) B) C) D) E) Ans:

I II III IV V C

HBr D2/Pd KMnO4, NaOH Cold

I II III IV V

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) Ans:

Both B and D 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) B)

HO

HO OH

C)

D)

E) Ans:

OH OH HO

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-3hexene with Br2 in the presence of methanol, CH3OH? Br

A)

B)

OMe Br MeO OMe

C)

D) E) Ans:

Br OMe Br

All of the above are produced in equal amounts 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? 1. HI 2. NaOMe, MeOH

I O

O

I

A) B) C) D) E) Ans:

II

I II III IV V B

III

IV

V

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

A) B) C) D) E) Ans:

II

III

IV

V

I II III IV V D

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

A) B) C) D) E) Ans:

II

I II III IV V C

III

IV

V

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

1. NaOEt, HOEt, heat 2a. Hg(OAc)2, CH3OH 2b. NaBH4, NaOH OCH3

OH H3C

OCH3 I

A) B) C) D) E) Ans:

OH II

III

IV

O

V

I II III IV V 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? Br

?

OH + enantiomer OH

I. MBA

A) B) C) D) E) Ans:

II. NaOCH2CH3, CH3CH2OH

I then II then III II then I then III II then IV III then I I then IV then II then III B

III. H3O+ or -OH

IV. 1) OsO4 then 2) NaHSO3/H2O

Topic: Synthetic Strategies Section: 9.13 Difficulty Level: Moderate 110. What is the expected major product of the following reaction sequence? 1. NaOEt, EtOH, heat 2a. BH3•THF 2b. H2O2, NaOH

Cl

HO HO

HO

OH

I

A) B) C) D) E) Ans:

I II III IV V C

OH

OH

OH

+ enantiomer

+ enantiomer

+ enantiomer

+ enantiomer

II

III

IV

V

Topic: Synthetic Strategies Section: 9.13 Difficulty Level: Moderate 111. What is the expected major product of the following reaction sequence? Br

1. NaOEt, EtOH, 70 °C 2a. O3, CH2Cl2, -78 °C 2b. DMS

H O

A)

O

OH

B)

OH O

C)

O O

CH

HC

D)

O

O O

E) Ans:

A

H

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

OH + enantiomer

A)

OH OH + enantiomer

B)

OH OH

+ enantiomer

C)

OH H

O +

O

D)

OH

H

OH + enantiomer

E) Ans:

OH

A

Topic: Synthetic Strategies Section: 9.13 Difficulty Level: Moderate 113. What is the expected major product of the following reaction sequence? 1. t-BuOK Cl 2. KMnO4, NaOH, cold

O

+

A)

OH

O

OH + CO2

B)

O

OH

C)

+ enantiomer

OH

OH

D)

+ enantiomer

OH + enantiomer

E) Ans:

OH

C

Topic: Synthetic Strategies Section: 9.13 Difficulty Level: Moderate 114. What is the expected major product of the following reaction sequence? 1. t-BuOK, t-BuOH

Cl

2a. O3, CH2Cl2 2b. Me2S

O

O

+ H

A)

H

O H

B)

O

OH OH

C) OH

D)

+ enantiomer

OH

O H

E) Ans:

+

H O

A

O

H

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

1. t-BuOK, t-BuOH 2. HBr

Br

Br

Br

Br

Cl

Br I

A) B) C) D) E) Ans:

II

III

IV

V

I II III IV V C

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

1. t-BuOK 2a. OsO4, pyridine 2b. H2O, NaHSO3 OH HO

A) OH

B)

OH

OH

C)

OH

D) Br

E)

OH

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

1. NaOEt, EtOH, 70 °C

H

2a. O3, CH2Cl2, -78 °C 2b. DMS O

A)

O

OH

B)

OH O

C)

O O

CH

HC

D)

O

O O

E) Ans:

E

H

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. Br

1. t-BuOK, t-BuOH 2a. BH3•THF 2b. H2O2, NaOH

HO

HO

HO

OH

A) B) C) D) E) Ans:

OH

II

I

I and II; III and IV; I and II; II and III; III and IV; D

OH

III

enantiomers enantiomers diastereomers diastereomers diastereomers

HO OH

IV

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. 1. NaOEt, HOEt, heat Br

A) B) C) D) E) Ans:

2a. Hg(OAc)2, CH3OH 2b. NaBH4, NaOH

2 total stereoisomers; 4 total stereoisomers; 4 total stereoisomers; 8 total stereoisomers; 8 total stereoisomers; E

1 set of enantiomers 2 sets of enantiomers 4 diastereoisomers 4 sets of enantiomers 8 diastereomers

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. 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: (CH3)2CHCH2CH CH2

Ans:

Br

HBr ROOR

?

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: H Cl

Cl–

Cl H Cl

most stable carbocation

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-2butene, are reacted with HCl the same major product is formed. Provide a mechanistic explanation for the observation. Ans: HCl Cl–

3,3-dimethyl-1-butene

Cl

HCl 2-chloro-2,3dimethylbutane 2,3-dimethyl-2-butene

most stable carbocation

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-2,3dimethylbutane.

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

H+

fast

I–

I

alternative 1 ring expansion

I–

alternative 2

I methyl shift

alternative 3

Ans:

I–

I

1,2 addition

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: OH OH

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. H

H 3O +

?

Ans: OH

H

H+

H O H

H Hydride shift

:B

O H H

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

O H

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. BH3•THF CH3CH2C(CH3)2CH CH2

Ans:

?

2. H2O2, NaOH

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

OH Br

Ans: 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. Br

Br2

+ HBr

HO

O

Ans: Br Br HO

Br HO

Br

Br Br–

O H

+ HBr O

!

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

?

OH

OH +

H Br

Ans:

H Br

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: Br2 H2O

HO H

CH(CH3)2 H Br C2H5

H Br

CH(CH3)2 OH H C2H5

H HO

CH(CH3)2 Br H C2H5

Br H

CH(CH3)2 H OH C2H5

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. O3

?

2. (CH3)2S, (DMS)

Ans: H

O O

and

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. H

Br2

?

CH3OH

H

H +

Ans:

Br

OCH3

Br

OCH3

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. KMnO4 cold, dil

Ans:

CH(CH3)2 H OH H OH C2H5

CH(CH3)2 HO H HO H C 2H 5

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. CH2CH3 H 3C OH H OH

OsO4 NMO

CH2CH3 HO CH3 HO H

C 2H 5

Ans:

C2H5

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 MBA, followed by acidic water. CH2CH3 HO CH3 H OH

1) MBA 2) H3O+

CH2CH3 H3C OH HO H

C 2H 5

Ans:

C2H5

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: 1) O3 2) DMS

O

OH

O OH

O

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

O

OH

–H+ O OH

Ans:

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

Br2

?

CH3OH

Ans: H

Br H

H

OCH3 CH3O H Br

Br Br

OCH3 H

H3CO Br

OCH3

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. MBA/CH2Cl2 iii. H3O+ Ans: Cl

H

H

H 3C H

t-BuOK/t-BuOH

MBA

(E2: Hofmann elimination)

(2R,3R)-2-chloro-3,4dimethylpentane

H3C H

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

CH2Cl2 syn addition

O

H

H

O +

H 3C H (R)-2-((R)1,2-dimethylmethylpropyl) oxirane

H 3C H (S)-2-((R)1,2-dimethylmethylpropyl) oxirane H 3O +

HO H HO H3C H (2S,3R)-3,4dimethylpentane-1,2-diol

H

OH

HO H3C H (2R,3R)-3,4dimethylpentane-1,2-diol

Hofmann elimination occurs upon heating with the bulky potassium tertbutoxide base, through an E2 elimination. Epoxidation with MBA 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 for the product shown. ?

1) MBA MeO

2) MeOH, [H2SO4]

OH

Ans: H O

O O

Cl O

H O

H O

H O O S OH O H3C

OH

H3C O H B:

H O H3C O

MeO

Step 1

Step 1 involves the epoxidation of the (E) alkene by MBA, 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 σ bond rotation has the same conformation as the product given in the question.

OH

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. explained as shown below:

This given data can be

C8H14 Reacts with Br2,CCl4: A must contain a π bond H2, Ni

A

A must contain the same carbon skeleton as the product after hydrogenation, and a π bond

ozonolysis O O

=

O

O

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

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