Organic Chemistry

180 CHAPTER 4 Reactions of Alkenes

45. For each of the following pairs, indicate which member is the more stable:

a. e.

b. f.

c. g.

d.

46. The second-order rate constant (in units of ) for acid-catalyzed hydration at 25 °C is given for each of the following
    alkenes:

a. Calculate the relative rates of hydration of the alkenes.

b. Why does (Z)-2-butene react faster than (E)-2-butene?

c. Why does 2-methyl-2-butene react faster than (Z)-2-butene?

d. Why does 2,3-dimethyl-2-butene react faster than 2-methyl-2-butene?

47. Which compound has the greater dipole moment?

a. c.

b.

48. a. What five-carbon alkene will form the same product whether it reacts with HBr in the presenceof a peroxide or with HBr in
    the absenceof a peroxide?
    b. Give three alkenes containing six carbon atoms that form the same product, whether they react with HBr in the presenceof a
    peroxide or with HBr in the absenceof a peroxide.


49. Mark Onikoff was about to turn in the products he had obtained from the reaction of HI with 3,3,3-trifluoropropene when he
    realized that the labels had fallen off his flasks. He didn’t know which label belonged to which flask. Another student in the next
    lab told him that because the product obtained by following Markovnikov’s rule was 1,1,1-trifluoro-2-iodopropane, he should put
    that label on the flask containing the most product and label the flask with the least product 1,1,1-trifluoro-3-iodopropane, the anti-
    Markovnikov product. Should Mark follow the student’s advice?


50. a. Propose a mechanism for the following reaction (show all curved arrows):

b. Which step is the rate-determining step?

c. What is the electrophile in the first step?

d. What is the nucleophile in the first step?

e. What is the electrophile in the second step?

f. What is the nucleophile in the second step?

CH 3 CH 2 CH CH 2 CH 3 OH CH 3 CH 2 CHCH 3

H+

+

OCH 3

or

Cl

H

H

H

CC

Cl

H

H

CH 3

CC

or

Cl

H

CH 3

H

CC

Cl

H

H

CH 3

or CC

H

H

H

Cl

CC

Cl

H

H

Cl

CC

CH 2

4.95 x 10−^8 8.32 x 10−^8 3.51 x 10−^8 2.15 x 10−^4 3.42 x 10−^4

H 3 C

H

C

H 3 C

H 3 C

CH 3

CH 3

CC

H 3 C

H

CH 3

CH 3

CC

H 3 C

H

H

CH 3

CC

H 3 C

H

CH 3

H

CC

M-^1 s-^1

CH 3 CH 2 CH 2 CHCH 3 or CH 3 CH 2 CH 2 CH 2 CH 2

CH 3 CHCHCH 3 or

Cl

+

CH 3 CHCH 2 CH 2

Cl

+

CH 3 CHCH 3 or CH 3 CHCH 2 Cl

+ +

CH 3

or

CH CH^3

3 CCH 2 or CH 3 CHCH 2 CH 3

CH 3

CH 3

CH 3 C CHCH 2 CH 3 or CH 3 CH

CH 3 CH 3

CH 3 CCH 3 or CH 3 CHCH 2 CH 3 CHCHCH 3

CH 3

+

+