Organic Chemistry

398 CHAPTER 10 Substitution Reactions of Alkyl Halides

39. For each of the following reactions, give the substitution products; if the products can exist as stereoisomers, show what
    stereoisomers are obtained:
    a. d. trans-1-chloro-2-methylcyclohexane
    b. (R)-2-bromopentane e. 3-bromo-2-methylpentane
    c. f. 3-bromo-3-methylpentane


40. Would you expect methoxide ion to be a better nucleophile if it were dissolved in or if it were dissolved in dimethyl
    sulfoxide (DMSO)? Why?


41. Which reaction in each of the following pairs will take place more rapidly?

a. c.

b. d.

42. Which of the following compounds would you expect to be more reactive in an reaction?


43. In Section 10.11, we saw that S-adenosylmethionine (SAM) methylates the nitrogen atom of noradrenaline to form adrenaline, a
    more potent hormone. If SAM methylates an OH group on the benzene ring instead, it completely destroys noradrenaline’s activity.
    Give the mechanism for the methylation of the OH group by SAM.


44. For each of the following reactions, give the substitution products; if the products can exist as stereoisomers, show what
    stereoisomers are obtained:
    a.
    b.
    c.
    d.
    e. 3-chloro-2,2-dimethylpentane
    f. benzyl bromide


45. Give the substitution products obtained when each of the following compounds is added to a solution of sodium acetate in
    acetic acid.
    a. 2-chloro-2-methyl-3-hexene
    b. 3-bromo-1-methylcyclohexene


46. The rate of reaction of methyl iodide with quinuclidine was measured in nitrobenzene, and then the rate of reaction of methyl
    iodide with triethylamine was measured in the same solvent.
    a. Which reaction had the larger rate constant?
    b. The same experiment was done using isopropyl iodide instead of methyl iodide. Which reaction had the larger rate constant?
    c. Which alkyl halide, has the larger ratio?

quinuclidine triethylamine

CH 2 CH 3

CH 3 CH 2 NCH 2 CH 3

N

ktriethylamine>kquinuclidine

+CH 3 CH 2 OH

+CH 3 CH 2 OH

(2R,3R)-2-chloro-3-methylpentane+high concentration of CH 3 O-

(2R,3S)-2-chloro-3-methylpentane+high concentration of CH 3 O-

(2S,3R)-2-chloro-3-methylpentane+high concentration of CH 3 O-

(2S,3S)-2-chloro-3-methylpentane+high concentration of CH 3 O-

norepinephrine a biologically inactive compound

HO CHCH 2 NH 2 SAM

HO

OH

+ HO CHCH 2 NH 2 SAH

CH 3 O

OH

+

H

CH 3

H

CH 3

Br

HorH

CH 3

H

CH 3

H

Br

SN 2

H 2 O

(CH 3 ) 3 CBr (CH 3 ) 3 COH

CH 3 CH 2 OH

(CH 3 ) 3 CBr (CH 3 ) 3 COCH 2 CH 3

+ HBr

+ HBr

HO−

O O

Cl OH + Cl−

HO− + Cl−

Cl OH

H 2 O

Cl

H 2 O

Cl

OH + HCl

OH + HCl

CH 3 S−

Cl

+

S

Cl−

(CH 3 ) 2 CHS−

Cl

+

S

Cl−

CH 3 OH

trans-1-chloro-2-methylcyclohexane+high concentration of CH 3 O- +CH 3 OH

+CH 3 OH +CH 3 OH

(R)-2-bromopentane+high concentration of CH 3 O- +CH 3 OH