Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman Chapter 6: Reactions of Alkenes - Addition Reactions 1. Which one of the following is not a metal catalyst for the hydrogenation of an alkene?
A) Pd B) Pt C) Na D) Ni
Ans: C
2. What is(are) the product(s) in the Pd-catalyzed hydrogenation of 1,2dimethylcyclopentene?
A) trans-1,2-dimethylcyclopentane
B) cis-1,2-dimethylcyclopentane
C) a mixture of trans and cis-1,2-dimethylcyclopentane
D) 1,1-dimethylcyclopentane
Ans: B
3. Which of the following alkenes is expected to have the highest heat of hydrogenation?
A) 1-pentene B) trans-2-pentene C) cis-2-pentene D) 2-methyl-2-butene
Ans: A
4. Which alkene below is thermodynamically the most stable?
A) 1-hexene B) trans-3-hexene C) cis-3-hexene D) 2-methyl-2-pentene
Ans: D
5. The stereochemical pathway for the hydrogenation of an alkene with a metal catalyst,
such as platinum, occurs via
A) syn addition.
C) Markovnikov addition.
B) anti addition.
D) anti-Markovnikov addition.
Ans: A
6. The product(s) in the following reaction is(are)
A)
B)
C)
D)
Ans:
only trans-1-4-dimethylcyclohexane.
only cis-1-4-dimethylcyclohexane.
both trans and cis-1-4-dimethylcyclohexane.
methylcyclohexane.
C
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1 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 7. What is the major product of the following reaction?
A) A B) B C) C D) D
Ans: B
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2 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 8. What is the intermediate in the following reaction?
A) A B) B C) C D) D
Ans: A
9. Which of the following is not a possible reaction of a carbocation?
A) addition of a nucleophile
B) rearrangement to a more stable carbocation
C) addition of a proton to form an alkane
D) loss of a β-hydrogen to form an alkene
Ans: C
10. Addition of HCl to 3-methyl-1-pentene gives two products. One of these is 2-chloro-3methylpentane. What is the other product?
A) 1-chloro-3-methylpentane
C) 3-chloro-2-methylpentane
B) 3-chloro-3-methylpentane
D) 2-chloro-2-methylpentane
Ans: B
11. Predict which of the following alkenes reacts the fastest with HCl.
A) CH3CH2CH2CH2CH=CH2
C) trans-CH3CH2CH=CHCH2CH3
B) cis-CH3CH2CH=CHCH2CH3
D) (CH3)2C=CHCH2CH3
Ans: D
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3 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 12. Which species below is the intermediate in the free radical addition of HBr to 1-butene?
A) A B) B C) C D) D
Ans: C
13. Which reagent(s) below would work best in converting 2-methyl-2-hexene to 2-methyl3-hexanol?
A) (1) H2SO4
(2) H2O
B) 50% H2SO4/H2O
C) (1) BH3/THF
(2) H2O2, NaOH
D) Br2/H2O
Ans: C
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4 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 14. What is the major product of the following reaction?
A) A B) B C) C D) D
Ans: A
15. What is(are) the product(s) of the following hydroboration-oxidation reaction?
A) 1-methylcyclobutanol
B) trans-2-methylcyclobutanol
Ans: B
C)
D)
cis-2-methylcyclobutanol
equal amounts of 2 and 3
16. The hydroboration-oxidation reaction can be characterized as the
___________________ to an alkene.
A) anti-Markovnikov syn addition of water
B) anti-Markovnikov anti addition of water
C) Markovnikov syn addition of water
D) Markovnikov anti addition of water
Ans: A
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5 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 17. What is the major product of the following reaction?
A) 1,2-dibromo-2-methylhexane
B) 2,2-dibromo-2-methylhexane
Ans: C
C)
D)
2,3-dibromo-2-methylhexane
2,4-dibromo-2-methylhexane
18. Which of the following alkenes gives 1-bromo-2-methyl-2-pentanol upon reaction with
Br2/H2O?
A) A B) B C) C D) D
Ans: D
19. Rank the following in order of decreasing reactivity with bromine, Br2.
A) I > II > III
Ans: A
B) II > III > I
C) III > I > II D) III > II > I
20. Which of the following is least likely to react with an alkene?
A) A B) B C) C D) D
Ans: D
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6 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 21. Which of the following series of reactions would convert cyclohexanol to 1,2epoxycyclohexane?
A) A B) B C) C D) D
Ans: C
22. Which species below acts as the nucleophile in the acid-catalyzed addition of water to
an alkene?
A) H3O+ B) the carbocation C) OH- D) H2O
Ans: D
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7 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 23. Addition of hypobromous acid, HOBr, to 1-methylcyclohexene gives:
A) A B) B C) C D) D
Ans: D
24. A compound, C15H24, is reacted with excess hydrogen using a metal catalyst. One
equivalent of the compound consumed three equivalents of hydrogen. How many rings
did the original compound have?
A) 1 only B) 2 only C) 3 only D) none
Ans: A
25. A compound, C20H30, can be hydrogenated with platinum metal and hydrogen to give a
compound C20H38. How many double bonds (DB) and rings (R) does the original
compound have? (The original compound has no triple bonds.)
A) 4 DB, 2 R B) 4 DB, 1 R C) 3 DB, 3 R D) 2 DB, 4 R
Ans: A
26. Determine the SODAR (sum of double bonds and rings) for a compound with the
formula of C6H9BrO.
A) one B) two C) three D) four
Ans: B
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8 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 27. The reaction of 1-butene with bromine, Br2, in aqueous solution gives primarily 1bromo-2-butanol. Identify the nucleophilic species in the reaction.
A) Br2 B)
Ans: C
C) H2O
D) HOBr
28. A compound is treated with ozone followed by zinc in water to give the following three
products. Which structure below best fits the data?
A) A B) B C) C D) D
Ans: B
29. Which of the following gives acetone, (CH3)2C=O, as one of the products of its
ozonolysis?
A) A B) B C) C D) D
Ans: D
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9 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 30. Which of the following species is the intermediate in the bromination of propene?
A) A B) B C) C D) D
Ans: C
31. A compound, C7H13Cl, is reacted with sodium ethoxide and gives a single elimination
product, C7H12. Treatment with ozone followed by zinc and water gives the compound
below. Identify the original compound.
A) 2-chloro-1,1-dimethylcyclopentane
B) 1-chloro-1,2-dimethylcyclopentane
Ans: D
C)
D)
4-chloro-1,2-dimethylcyclopentane
2-chloro-1,3-dimethylcyclopentane
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10 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 32. Which of the following correctly depicts the mechanistic first step in the addition of
HBr to 2-methylpropene?
A) A B) B C) C D) D
Ans: A
33. The rearrangement which occurs in the following reaction can be described as a
A) hydride shift from C-2 to C-1.
B) hydride shift from C-3 to C-2.
Ans: B
C)
D)
proton shift from C-2 to C-1.
methyl group shift from C-3 to C-2.
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11 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 34. Which structure corresponds to the trimer of (CH3)2C=CH2 formed under conditions of
cationic polymerization?
A) A B) B C) C D) D
Ans: A
35. Which of the following does not give 1-bromo-1-methylcyclopentane as the major
product?
A) A B) B C) C D) D
Ans: A
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12 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 36. Which point on the potential energy diagram corresponds to the species below for the
reaction of 2-methylpropene with hydrogen chloride?
A) A B) B C) C D) D
Ans: B
37. Identify the nucleophile in the following electrophilic addition reaction.
A) A B) B C) C D) D
Ans: B
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13 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 38. Which of the following is the rate-determining step in the acid-catalyzed addition of
water to 2-methylpropene?
A) A B) B C) C D) D
Ans: A
39. Which reaction sequence below would work best in converting 3-pentanol into 2,3dibromopentane?
A) A B) B C) C D) D
Ans: D
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14 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 40. Which reaction proceeds by anti addition?
A) A B) B C) C D) D
Ans: A
41. Which point on the potential energy diagram corresponds to the carbocation
intermediate, (CH3)3C+, for the reaction shown below?
A) A B) B C) C D) D
Ans: B
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15 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 42. Which of the following reactions occurs by a one-step mechanism as opposed to a twostep mechanism?
A) A B) B C) C D) D
Ans: B
43. What is the product in the following reaction?
A) (CH3CH2CH2)3B B) [(CH3)2CH]3B C) CH3CH2CH3
Ans: A
D) polypropylene
44. Identify the following polymer.
A) polyethylene B) polypropylene
Ans: B
C) polyisobutylene
D) polybutylene
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16 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 45. Which of the following is the product of the reaction shown below?
A) A B) B C) C D) D
Ans: B
46. Identify the electrophilic species in the following reaction.
A) H2C=C(CH3)2
Ans: C
B) H2O
C) H3O+
D) (CH3)3COH
47. Which of the following is the key intermediate in the Markovnikov addition of HBr to
1-butene?
A) A B) B C) C D) D
Ans: D
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17 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 48. Which reagent(s) below would convert 2-methyl-2-pentene to 2-methyl-2-pentanol
(shown below)?
A) (1) O3 (2) Zn, H2O
B) (1) BH3/THF (2) H2O2, NaOH
Ans: D
C)
D)
Br2/H2O
H2O/H2SO4 (cat.)
49. What product results from this reaction?
Cl2
?
H2O
OH
OH
Cl
CH3
A
Cl
OH
CH3
Cl
B
Cl
CH3
CH3
C
OH
D
A) A B) B C) C D) D
Ans: B
50. Which of the alcohols below could NOT be prepared using hydroboration/oxidation of
an alkene?
OH
A
C
OH
B
D
OH
OH
A) A B) B C) C D) D
Ans: C
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18 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 51. Which brief statement most accurately describes why alkenes react the way they do?
A) C=C double bonds are weak.
B) a π bond is lost but a stronger σ bond is gained.
C) C=C double bonds are unstable.
D) C=C π bonds are attacked by nucleophiles.
Ans: B
52. What major product would you expect from this reaction?
H
H
C
CH3
H2O
CH3
cat. H2SO4
C
C
?
CH3
H
A) 3,3-dimethyl-2-butanol
B) 3,3-dimethyl-1-butanol
Ans: C
C)
D)
2,3-dimethyl-2-butanol
2,2-dimethyl-3-butanol
H3C
CH3
53. What product results from this reaction?
H3C
A
2
C
O
B
H3C
C
H3C
H3C
CH3
O
CH3
H3C
C
C
C
HO
C
CH3
OH
CH3
H3C
D
H3C
C
C
H
OH
CH3
A) A B) B C) C D) D
Ans: B
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19 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 54. What product results from this reaction?
1. O3
?
2. Zn or Me2S
OH
OH
A
B
OH
OH
O
C
D
O
O
A) A B) B C) C D) D
Ans: D
55. How many of these reagents cause only syn additions to alkenes?
HBr
H2, catalyst
BH3
CH3CO3H
A) 1 B) 2
Ans: C
C) 3
Br2
D) 4
56. What reagents would be required to accomplish the conversion shown below?
Br
make
Br
into
CH3
A) NaOCH3, then Br2 and light.
B) KOCH3, then HBr and peroxides.
Ans: B
CH3
C)
D)
NaOCH3, then HBr.
KOtBu, then Br2 and light.
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20 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.
Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman 57. The polymerization of styrene gives a polymer that has which structure?
styrene
Ph
Ph
A.
Ph
Ph
n
B.
Ph
Ph
Ph
n
Ph
Ph
Ph
C.
D. none of these
Ph
Ph
n
A) A B) B C) C D) D
Ans: A
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21 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.