Chapter 6 Homework Answers PDF

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CHAPTER 6—REACTIONS OF ALKENES MULTIPLE CHOICE 1.

What type of carbocation is shown?

a. primary b. secondary c. tertiary d. quaternary ANS: B 2.

What type of carbocation is shown?

a. primary b. secondary c. tertiary d. quaternary ANS: C 3. Which of the following concepts explains why tertiary carbocations are more stable than primary and secondary carbocations? a. electronegativity b. resonance c. hyperconjugation d. the octet rule ANS: C 4. What type of orbitals overlap to provide stability to the tert-butyl carbocation by hyperconjugation?

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a. 3° C 2p atomic orbital + 3° C sp2 atomic orbital b. 3° C 2p atomic orbital + methyl C−H σ molecular orbital c. 3° C sp2 atomic orbital + methyl C−H σ molecular orbital d. 3° C 2p atomic orbital + methyl C 2s atomic orbital ANS: B 5. Which of the following concepts explains Markovnikov's rule as applied to the addition of HBr to propene? a. the relative stability of carbocations b. the nucleophilicity of bromide anion c. the acidity of HBr d. the aufbau principle ANS: A 6.

What is the correct order of stability of the following carbocations (more stable > less

stable)?

a. 1 > 2 > 3 b. 1 > 3 > 2 c. 3 > 1 > 2 d. 3 > 2 > 1 ANS: D

8.

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What is the major organic product obtained from the following reaction?

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a. 1 b. 2 c. 3 d. 4 ANS: B 9.

What is the major organic product obtained from the following reaction?

a. 1 b. 2 c. 3 d. 4 ANS: B

10.

What is the major organic product obtained from the following reaction?

a. 1 b. 2 c. 3 d. 4 ANS: C 11.

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What is the major organic product obtained from the following reaction?

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a. 1 b. 2 c. 3 d. 4 ANS: C 12. Which of the following alkenes is most likely to undergo rearrangement upon acidcatalyzed hydration (treatment with aqueous H2SO4)?

a. 1 b. 2 c. 3 d. 4 ANS: B 13. Which of the following alkenes is most likely to undergo rearrangement upon acidcatalyzed hydration (treatment with aqueous H2SO4)?

a. 1 b. 2 c. 3 d. 4 ANS: B 14.

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What is the major organic product obtained from the following reaction?

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a. 1 b. 2 c. 3 d. 4 ANS: C 15.

What is the major organic product obtained from the following reaction?

a. 1 b. 2 c. 3 d. 4 ANS: C 16.

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What is the major organic product obtained from the following reaction?

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a. 1 b. 2 c. 3 d. 4 ANS: B 17.

What is the major organic product obtained from the following reaction?

a. 1 b. 2 c. 3 d. 4 ANS: B 18.

What is the major organic product obtained from the following reaction?

a. 1 b. 2 c. 3 d. 4 ANS: B 19.

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What is the major organic product obtained from the following reaction?

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a. 1 b. 2 c. 3 d. 4 ANS: C 20.

What is the major organic product obtained from the following reaction?

a. 1 b. 2 c. 3 d. 4 ANS: B 21.

What is the major organic product obtained from the following reaction?

a. 1 b. 2 c. 3 d. 4

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ANS: B 22.

What is the major organic product obtained from the following reaction?

a. 1 b. 2 c. 3 d. 4 ANS: C

a. 1

c. 3 d. 4 ANS: B 24.

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What is the major organic product obtained from the following reaction?

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a. 1 b. 2 c. 3 d. 4 ANS: C 25.

What is the major organic product obtained from the following reaction?

a. 1 b. 2 c. 3 d. 4 ANS: D

a. (1R,2R,4R)-1,2-dibromo-4-tert-butylcyclohexane b. (1S,2R,4R)-1,2-dibromo-4-tert-butylcyclohexane

d. (1S,2S,4S)-1,2-dibromo-4-tert-butylcyclohexane ANS: C 27.

What is (are) the major organic product(s) obtained from the following reaction?

1.

(2R,3R)-dibromobutane

2.

(2S,3S)-dibromobutane

3.

meso-2,3-dibromobutane

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a. only 1 b. only 2 c. only 3 d. only 1 and 2 ANS: C

1.

(2R,3R)-dibromobutane

2.

(2S,3S)-dibromobutane

3.

meso-2,3-dibromobutane

a. only 1 b. only 2 c. only 3

ANS: D

a. 1

c. 3 d. 4 ANS: B

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30.

What is the major organic product obtained from the following reaction?

a. 1 b. 2 c. 3 d. 4 ANS: A 31.

What is the major organic product obtained from the following reaction?

a. 1 b. 2 c. 3 d. 4 ANS: D 32.

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What is (are) the major organic product(s) obtained from the following reaction?

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1.

(2R,3R)-butanediol

2.

(2S,3S)-butanediol

3.

meso-2,3-butanediol

a. only 1 b. only 2 c. only 3 d. only 1 and 2 ANS: D

1.

(2R,3R)-butanediol

2.

(2S,3S)-butanediol

3.

meso-2,3-butanediol

a. only 1 b. only 2

d. only 1 and 2 ANS: C

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b. only 2 c. only 3 d. only 2 and 3 ANS: A 35.

What is the best choice of reagent(s) to perform the following transformation?

a. H2O, H2SO4 b. HgSO4; followed by NaBH4 c. BH3; followed by H2O2 d. OsO4; followed by NaHSO3 ANS: D 37.

What is the best choice of reagent(s) to perform the following transformation?

a. H2O, H2SO4 b. Hg(OAc)2 and H2O ; followed by NaBH4 c. B2H6; followed by H2O2, NaOH d. OsO4; followed by NaHSO3 ANS: C 38.

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What is the best choice of reagent(s) to perform the following transformation?

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a. O3; followed by (CH3)2S b. Hg(OAc)2 and H2O; followed by NaBH4 c. BH3; followed by H2O2, NaOH d. OsO4; followed by NaHSO3 ANS: A 39.

What is the best choice of reagent(s) to perform the following transformation?

a. H2O, H2SO4 b. Hg(OAc)2 and H2O; followed by NaBH4 c. BH3; followed by H2O2, NaOH d. OsO4; followed by NaHSO3 ANS: B 40. What type of reactive intermediate is formed in the reaction of an alkene with HBr to give a bromoalkane? a. carbocation b. carbanion c. radical d. cyclic bromonium ion ANS: A 41. What type of reactive intermediate is formed in the reaction of an alkene with Br2 and water to give a bromohydrin? a. carbocation b. carbanion c. radical d. cyclic bromonium ion ANS: D 42. What type of reactive intermediate is formed in the reaction of an alkene with aqueous acid to give an alcohol?

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a. carbocation b. carbanion c. radical d. carbene ANS: A 43. What type of reaction mechanism accounts for the reaction of an alkene with aqueous acid to give an alcohol? a. nucleophilic addition b. electrophilic addition c. radical addition d. elimination ANS: B 44. What type of reaction mechanism accounts for the reaction of an alkene with HBr to give an alkyl bromide? a. nucleophilic addition b. electrophilic addition c. radical addition d. elimination ANS: B 45. Which of the following alkenes undergoes the most exothermic hydrogenation upon treatment with H2/Pd?

a. 1 b. 2 c. 3 d. 4 ANS: D 46. Which of the following alkenes undergoes the least exothermic hydrogenation upon treatment with H2/Pd?

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a. 1 b. 2 c. 3 d. 4 ANS: C 47. What is the correct order of exothermicity for hydrogenation of the following butenes upon treatment with H2/Pd (more exothermic > less exothermic)?

a. 1 > 2 > 3 b. 1 > 3 > 2 c. 3 > 2 > 1 d. 2 > 3 > 1 ANS: A 48.

What is (are) the major organic product(s) obtained from the following reaction?

1.

(R)-2-bromo-3-methylbutane

2.

(S)-2-bromo-3-methylbutane

3.

2-bromo-2-methylbutane

a. only 1 b. only 2 c. only 3 d. only 1 and 2 ANS: C

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49.

What is (are) the major organic product(s) obtained from the following reaction?

1.

(R)-3-methyl-2-butanol

2.

(S)-3-methyl-2-butanol

3.

2-methyl-2-butanol

a. only 1 b. only 2 c. only 3 d. only 1 and 2 ANS: D 50.

Which of the following reactions of alkenes is not stereospecific?

a. bromination (treatment with Br2 in CHCl3) b. hydrogenation (treatment with H2/Pt) c. acid-catalyzed hydration (treatment with aqueous H2SO4) d. bromohydrin formation (treatment with Br2/H2O) ANS: C 51.

Which of the following reactions of alkenes is stereospecific?

a. addition of HCl (treatment with HCl) b. hydrogenation (treatment with H2/Pt) c. addition of HBr (treatment with HBr) d. acid-catalyzed hydration (treatment with aqueous H2SO4) ANS: B 52.

Which of the following reactions of alkenes takes place with anti stereospecificity?

a. bishydroxylation (treatment with OsO4 followed by NaHSO3) b. hydrogenation (treatment with H2/Pt) c. addition of HBr (treatment with HBr) d. bromohydrin formation (treatment with Br2, H2O) ANS: D 53.

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Which of the following reactions of alkenes takes place with syn stereospecificity?

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a. addition of bromine (treatment with Br2) b. hydrogenation (treatment with H2/Pt) c. addition of HBr (treatment with HBr) d. acid-catalyzed hydration (treatment with aqueous H2SO4) ANS: B TRUE/FALSE 1.

The reagents that could effect the following conversion are H2 and Ni.

!

ANS: T 2.

The reagents that could effect the following conversion are: BH3, then H2O2 and

NaOH.

!

ANS: F 3.

Consider the following reaction.

! The product would be

!

ANS: F

The products obtained by the acid-catalyzed hydration of 1-methylcyclohexene and methylenecyclohexene are identical. 4.

ANS: T

6.

Markovnikov addition of HCl to propene involves the formation of a secondary

carbocation. BIAF 7e

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ANS: T 7.

Br2 in CCl4 can be used to distinguish cyclohexene from cyclohexane.

ANS: T

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8.

Consider the following reaction.

! The mechanism for this reaction is shown below.

! ANS: T 9. If the following compound were dissolved in ether and treated with HCl, the product of the reaction would a mixture of 3-bromoheptane and 2-bromoheptane.

! ANS: T COMPLETION

_____________is the starting material required to produce 3-methyl-1-butanol using the hydroboration-oxidation reaction. (Enter an IUPAC name.) 1.

ANS: 3-methyl-1-butene

2. Upon ozonolysis, _____________ will produce only acetone, (CH3)2C=O. (Enter an IUPAC name.) ANS: 2,3-dimethyl-2-butene 3. ____________________ predicts that the more stable carbocation intermediate is formed in electrophilic additions to alkenes. ANS: Markovnikov's rule

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4.

Consider the following reactions.

Pathway ___ involves a 1,2-shift. ANS: b The reaction of methylpropene with HBr in ether gives one of the two products below as the major product. Answer the following question(s) about this reaction.

5.

Product _____would be the major product.

ANS: B 6.

Product _____would be formed via a primary carbocation.

ANS: A 7. Product _____ would have a higher energy transition state for the formation of the intermediate leading to it. ANS: A 8.

Product _____ is the non-Markovnikov product.

ANS: A 9. Product _____ would be formed by a carbocation experiencing the greatest degree of hyperconjugation stabilization. ANS: B

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10. Product _____ would have the lowest activation energy required to form the intermediate in the mechanism. ANS: B PROBLEM 1.

What is the major organic product obtained from the following reaction?

2.

What is the major organic product obtained from the following reaction?

3.

What is the major organic product obtained from the following reaction?

4.

What is the major organic product obtained from the following reaction?

ANS:

ANS:

ANS:

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ANS:

5.

What is the major organic product obtained from the following reaction?

6.

What is the major organic product obtained from the following reaction?

7.

What is the major organic product obtained from the following reaction?

ANS:

ANS:

ANS:

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8.

What is the major organic product obtained from the following reaction?

9.

What is the major organic product obtained from the following reaction?

ANS:

ANS: 2 equivalents of

10.

What is the major organic product obtained from the following reaction?

11.

What is the major organic product obtained from the following reaction?

ANS:

ANS:

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12.

What is the best choice of reagent(s) to perform the following transformation?

ANS: (i) BH3; (ii) H2O2, NaOH 13.

What is the best choice of reagent(s) to perform the following transformation?

ANS: H2O, H2SO4 or (i) Hg(OAc)2, H2O; (ii) NaBH4 14.

What is the best choice of reagent(s) to perform the following transformation?

ANS: (i) OsO4; (ii) NaHSO3, H2O 15.

What is the best choice of reagent(s) to perform the following transformation?

ANS: H2, transition metal catalyst (e.g., Pt, Pd) 16.

What is the best choice of reagent(s) to perform the following transformation?

ANS: Br2 17.

What is the best choice of reagent(s) to perform the following transformation?

ANS: Br2, H2O

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18.

What is the best choice of reagent(s) to perform the following transformation?

ANS: HBr 19.

What is the best choice of reagent(s) to perform the following transformation?

ANS: (i) O3 (ii) (CH3)2S 20.

Provide the structure of the key intermediate in the following reaction?

21.

Provide the structure of the key intermediate in the following reaction?

22.

Provide the structure of the key intermediate in the following reaction?

ANS:

ANS:

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ANS:

23. Provide a neatly drawn mechanism for the following reaction, including curved arrows to show the movement of pairs of electrons and the structure of reactive intermediates.

ANS: The reaction proceeds in two steps: 1. Protonation of propene to form the 2-propyl cation 2. Nucleophilic addition of bromide anion to the 2-propyl cation

24. Provide a neatly drawn mechanism for the following reaction, including curved arrows to show the movement of pairs of electrons and the structure of reactive intermediates.

ANS: The reaction proceeds in three steps: 1. Protonation of propene to form the 2-propyl cation 2. Nucleophilic addition of bromine to the 2-propyl cation 3. Deprotonation of the oxygen

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25. Provide a neatly drawn mechanism for the following reaction, including curved arrows to show the movement of pairs of electrons and the structure of reactive intermediates.

ANS: The reaction proceeds in two steps: 1. Addition of bromine to propene to afford a cyclic bromonium ion 2. Nucleophilic ring-opening addition of bromide anion

26. Provide a neatly drawn mechanism for the following reaction, including curved arrows to show the movement of pairs of electrons and the structure of reactive intermediates.

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ANS: The reaction proceeds in three steps: 1. Addition of bromine to propene to afford a cyclic bromonium ion 2. Nucleophilic ring-opening addition of water 3. Deprotonation of oxygen

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