CHAPTER 6—REACTIONS OF ALKENES
MULTIPLE CHOICE
1. What type of carbocation is shown?
a. b. c. d.
primary secondary tertiary quaternary
ANS: B 2. What type of carbocation is shown?
a. b. c. d.
primary secondary tertiary quaternary
ANS: C 3. Which of the following concepts concepts explains why why tertiary carbocations 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 orbitals overlap to provide provide stability stability to the tert- butyl butyl carbocation by hyperconjugation? hyperconjugation? 2 a. 3° C 2 p atomic p atomic orbital + 3 ° C sp C sp atomic orbital b. 3° C 2 p atomic orbital + methyl C −H σ molecular orbital c. 3° C sp C sp2 atomic orbital + methyl C −H σ molecular orbital d. 3° C 2 p atomic orbital + methyl C 2 s atomic s atomic orbital ANS: B 5. Which of the following concepts concepts explains Markovnikov's Markovnikov's rule rule as applied to the addition of HBr to propene? a. the relative stability of carbocations b. the nucleophilicity nucleophilicity of bromide anion c. the acidity of HBr d. the Aufbau principle
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ANS: A 6. What is the correct correct order of stability stability of the following following carbocations carbocations (more stable stable > less stable)?
a. b. c. d.
1 > 2 > 3 1 > 3 > 2 3 > 1 > 2 3 > 2 > 1
ANS: D 7. What is the correct correct order of stability stability of the following following carbocations carbocations (more stable stable > less stable)?
a. b. c. d.
1 > 2 > 3 2 > 1 > 3 2 > 3 > 1 3 > 2 > 1
ANS: C 8. What is the the major organic organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: B
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9. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: B 10. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: C 11. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: C
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12. Which of the following alkenes is most likely to undergo rearrangement upon acid-catalyzed hydration (treatment with aqueous H 2SO4)?
a. b. c. d.
1 2 3 4
ANS: B 13. Which of the following alkenes is most likely to undergo rearrangement upon acid-catalyzed hydration (treatment with aqueous H 2SO4)?
a. b. c. d.
1 2 3 4
ANS: B 14. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: C
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15. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: C 16. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: B 17. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: B
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18. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: B 19. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: C 20. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: B
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21. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: B 22. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: C 23. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: B
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24. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: C 25. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: D 26. What is the major product obtained upon addition of Br 2 to ( R)-4-tert -butylcyclohexene? a. (1 R,2 R,4 R)-1,2-dibromo-4-tert -butylcyclohexane b. (1S ,2 R,4 R)-1,2-dibromo-4-tert -butylcyclohexane c. (1S ,2S ,4 R)-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. 2. 3.
a. b. c. d.
(2 R,3 R)-dibromobutane (2S ,3S )-dibromobutane meso-2,3-dibromobutane only 1 only 2 only 3 only 1 and 2
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ANS: C 28. What is (are) the major organic product(s) obtained from the following reaction?
(2 R,3 R)-dibromobutane (2S ,3S )-dibromobutane meso-2,3-dibromobutane
1. 2. 3.
a. b. c. d.
only 1 only 2 only 3 only 1 and 2
ANS: D 29. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: B 30. What is the major organic product obtained from the following reaction?
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a. b. c. d.
1 2 3 4
ANS: A 31. What is the major organic product obtained from the following reaction?
a. b. c. d.
1 2 3 4
ANS: D 32. What is (are) the major organic product(s) obtained from the following reaction?
1. 2. 3.
a. b. c. d.
(2 R,3 R)-butanediol (2S ,3S )-butanediol meso-2,3- butanediol only 1 only 2 only 3 only 1 and 2
ANS: D
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33. What is (are) the major organic product(s) obtained from the following reaction?
1. 2. 3.
a. b. c. d.
(2 R,3 R)-butanediol (2S ,3S )-butanediol meso-2,3- butanediol only 1 only 2 only 3 only 1 and 2
ANS: C 34. What is (are) the major organic product(s) obtained from the following reaction?
a. b. c. d.
only 1 only 2 only 3 only 2 and 3
ANS: A 35. What is the best choice of reagent(s) to perform the following transformation?
a. b. c. d.
H2O, H2SO4 HgSO4; followed by NaBH 4 BH3; followed by H 2O2 OsO4; followed by NaHSO 3
ANS: D
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36. What is the best choice of reagent to perform the following transformation?
a. b. c. d.
Br 2 HBr Br 2, H2O N -bromosuccinimide
ANS: C 37. What is the best choice of reagent(s) to perform the following transformation?
a. b. c. d.
H2O, H2SO4 Hg(OAc)2 and H2O ; followed by NaBH 4 B2H6; followed by H 2O2, NaOH OsO4; followed by NaHSO 3
ANS: C 38. What is the best choice of reagent(s) to perform the following transformation?
a. b. c. d.
O3; followed by (CH 3)2S Hg(OAc)2 and H2O; followed by NaBH 4 BH3; followed by H 2O2, NaOH OsO4; followed by NaHSO 3
ANS: A
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39. What is the best choice of reagent(s) to perform the following transformation?
a. b. c. d.
H2O, H2SO4 Hg(OAc)2 and H2O; followed by NaBH 4 BH3; followed by H 2O2, NaOH OsO4; followed by NaHSO 3
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 Br 2 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? 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
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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. b. c. d.
1 2 3 4
ANS: D 46. Which of the following alkenes undergoes the least exothermic hydrogenation upon treatment with H2/Pd?
a. b. c. d.
1 2 3 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. b. c. d.
1 > 2
>3 1 > 3 > 2 3 > 2 > 1 2 > 3 > 1
ANS: A
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48. What is (are) the major organic product(s) obtained from the following reaction?
1. 2. 3.
a. b. c. d.
( R)-2-bromo-3-methylbutane (S)-2-bromo-3-methylbutane 2-bromo-2-methylbutane only 1 only 2 only 3 only 1 and 2
ANS: C 49. What is (are) the major organic product(s) obtained from the following reaction?
1. 2. 3.
a. b. c. d.
( R)-3-methyl-2-butanol (S)-3-methyl-2-butanol 2-methyl-2-butanol only 1 only 2 only 3 only 1 and 2
ANS: D 50. Which of the following reactions of alkenes is not stereospecific? a. bromination (treatment with Br 2 in CHCl3) b. hydrogenation (treatment with H 2/Pt) c. acid-catalyzed hydration (treatment with aqueous H 2SO4) d. bromohydrin formation (treatment with Br 2/H2O) ANS: C 51. Which of the following reactions of alkenes is stereospecific? a. addition of HCl (treatment with HCl) b. hydrogenation (treatment with H 2/Pt) c. addition of HBr (treatment with HBr) d. acid-catalyzed hydration (treatment with aqueous H 2SO4) ANS: B
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52. Which of the following reactions of alkenes takes place with anti stereospecificity? a. bishydroxylation (treatment with OsO 4 followed by NaHSO 3) b. hydrogenation (treatment with H 2/Pt) c. addition of HBr (treatment with HBr) d. bromohydrin formation (treatment with Br 2, H2O) ANS: D 53. Which of the following reactions of alkenes takes place with syn stereospecificity? a. addition of bromine (treatment with Br 2) b. hydrogenation (treatment with H 2/Pt) c. addition of HBr (treatment with HBr) d. acid-catalyzed hydration (treatment with aqueous H 2SO4) ANS: B PROBLEM
1. What is the major organic product obtained from the following reaction?
ANS:
2. What is the major organic product obtained from the following reaction?
ANS:
3. What is the major organic product obtained from the following reaction?
ANS:
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4. What is the major organic product obtained from the following reaction?
ANS:
5. What is the major organic product obtained from the following reaction?
ANS:
6. What is the major organic product obtained from the following reaction?
ANS:
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7. What is the major organic product obtained from the following reaction?
ANS:
8. What is the major organic product obtained from the following reaction?
ANS:
9. What is the major organic product obtained from the following reaction?
ANS: 2 equivalents of
10. What is the major organic product obtained from the following reaction?
ANS:
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11. What is the major organic product obtained from the following reaction?
ANS:
12. What is the best choice of reagent(s) to perform the following transformation?
ANS: (i) BH3; (ii) H 2O2, 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)
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16. What is the best choice of reagent(s) to perform the following transformation?
ANS: Br 2 17. What is the best choice of reagent(s) to perform the following transformation?
ANS: Br 2, H2O
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?
ANS:
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21. Provide the structure of the key intermediate in the following reaction?
ANS:
22. Provide the structure of the key intermediate in the following reaction?
ANS:
23. Provide a neatly drawn mechanism for the following reaction, including curved arrows to show the movement of paris 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
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24. Provide a neatly drawn mechanism for the following reaction, including curved arrows to show the movement of paris 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
25. Provide a neatly drawn mechanism for the following reaction, including curved arrows to show the movement of paris of electrons and the structure of reactive intermediates.
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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 paris of electrons and the structure of reactive intermediates.
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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