Organic Chemistry

(Dana P.) #1
PROBLEM 15

Arrange the following alkyl halides in order of decreasing reactivity in an reaction:
2-bromopentane, 2-chloropentane, 1-chloropentane, 3-bromo-3-methylpentane.

PROBLEM 16

Which of the following alkyl halides form a substitution product in an reaction that is
different from the substitution product formed in an reaction?

a. c. e.

b. d. f.

PROBLEM 17

Two substitution products result from the reaction of 3-chloro-3-methyl-1-butene with
sodium acetate in acetic acid under conditions. Identify the products.

10.7 More About the Stereochemistry


of and Reactions


The Stereochemistry of Reactions
The reaction of 2-bromopropane with hydroxide ion forms a substitution product
without any asymmetric carbons. The product, therefore, has no stereoisomers.

The reaction of 2-bromobutane with hydroxide ion forms a substitution product with
an asymmetric carbon. The product, therefore, can exist as enantiomers.

We cannot specify the configuration of the product formed from the reaction of
2-bromobutane with hydroxide ion unless we know the configuration of the alkyl
halide and whether the reaction is an or an reaction. For example, if we know
that the reaction is an reaction and that the reactant has the Sconfiguration, we
know that the product will be (R)-2-butanol because in an reaction, the incoming
nucleophile attacks the back side of the carbon that is attached to the halogen
(Section 10.2). Therefore, the product will have a configuration that is inverted relative
to that of the reactant. (Recall that an reaction takes place with inversion of
configuration).

SN 2

SN 2

SN 2

SN 2 SN 1

Br
2-bromobutane 2-butanol

CH 3 CHCH 2 CH 3 + HO− CH 3 CHCH 2 CH 3 + Br−

OH

asymmetric carbon asymmetric carbon

2-bromopropane 2-propanol

CH 3 CHCH 3 + HO− CH 3 CHCH 3 + Br−

Br OH

SN 2


SN 2 SN 1


(CH 3 COO- Na+) SN 1

CH 3

CH Br
3 CHCH 2 CCH 3

CH 3

Cl CH 3

CH 3

Cl

CH 2 Br

CH 3 CH 2 C CHCH 3

CH 3

CH 3 Br

CH 3 CHCHCHCH 3

CH 3 Br

CH 3

SN 2

SN 1

SN 1

380 CHAPTER 10 Substitution Reactions of Alkyl Halides

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