Organic Chemistry

154 CHAPTER 4 Reactions of Alkenes

Synthetic Tutorial:

Addition of alcohol to an

alkene

Frank (Rocky) Clifford Whitmore
(1887–1947)was born in Massachu-
setts. He received a Ph.D. from
Harvard University and was a profes-
sor of chemistry at Minnesota,
Northwestern, and Pennsylvania
State Universities. Whitmore never
slept a full night; when he got tired,
he took a one-hour nap. Consequent-
ly, he had the reputation of being an
indefatigable worker; 20-hour work-
days were common. He generally had
30 graduate students working in his
lab at a time, and he wrote an ad-
vanced textbook that was considered
a milestone in the field of organic
chemistry.

3,3-dimethyl-1-butene 3-chloro-2,2-dimethylbutane

minor product

2-chloro-2,3-dimethylbutane

major product

CH 3 CCHCH 2 + HCl CH 3 CCHCHCH 3 + 3 C CHCH 3

CH 3

CH 3 Cl

CH 3

Cl CH 3

CH 3

CH 3

PROBLEM 11

How could the following compounds be prepared, using an alkene as one of the starting

materials?

a. d.

b. e.

c. f.

PROBLEM 12

Propose a mechanism for the following reaction (remember to use curved arrows when

showing a mechanism):

4.6 Rearrangement of Carbocations

Some electrophilic addition reactions give products that are clearly not the result of the

addition of an electrophile to the carbon bonded to the greater number of hydro-

gens and the addition of a nucleophile to the other carbon. For example, the addi-

tion of HBr to 3-methyl-1-butene forms 2-bromo-3-methylbutane (minor product) and

2-bromo-2-methylbutane (major product). 2-Bromo-3-methylbutane is the product

you would expect from the addition of to the carbon bonded to the greater

number of hydrogens and to the other carbon. 2-Bromo-2-methylbutane is an

“unexpected”product, even though it is the major product of the reaction.

In another example, the addition of HCl to 3,3-dimethyl-1-butene forms both

3-chloro-2,2-dimethylbutane (an “expected”product) and 2-chloro-2,3-dimethylbu-

tane (an “unexpected product”). Again, the unexpected product is obtained in greater

yield.

3-methyl-1-butene

2-bromo-3-methylbutane

minor product

2-bromo-2-methylbutane

major product

CH 3 CHCH CH 2 + HBr CH 3 CHCHCH 3 + CH 3 CCH 2 CH 3

CH 3 CH 3

Br Br

CH 3

Br- sp^2

H+ sp^2

sp^2

sp^2

CH 3 CHCH 2 CH 2 OH + CH 3 CCHCH 2 3 CHCH 2 CH 2 OCCH 3

CH 3 CH 3 CH 3

CH 3

CH 3

H+

CH 3 CH 2 CHCH 2 CH 2 CH 3

CH 3 OH

CH 3 CH 2 OCHCH 2 CH 3

CH 3 OH

CH 3

CH 3 OCCH 3

CH 3 CHCH 2 CH 3

OH

OCH 3