Organic Chemistry

Section 4.12 Reactions and Synthesis 175

You will learn how alkenes are synthesized when you study compounds that undergo
elimination reactions. The various reactions that result in the synthesis of alkenes are
listed in Appendix IV.

PROBLEM 30 SOLVED

Starting with an alkene, indicate how each of the following compounds can be synthesized:

a. b. c.

SOLUTION

a. The only alkene that can be used for this synthesis is cyclohexene. To get the desired

substituents on the ring, cyclohexene must react with in an aqueous solution so that

water will be the nucleophile.

b. The alkene that should be used here is 1-methylcyclohexene. To get the substituents in

the desired locations, the electrophile in the reaction must be a bromine radical. There-

fore, the reagents required to react with 1-methylcyclohexene are HBr and a peroxide.

c. In order to synthesize an alkane from an alkene, the alkene must undergo catalytic hy-

drogenation. Several alkenes could be used for this synthesis.

PROBLEM 31

Why should 3-methylcyclohexene not be used as the starting material in Problem 30b?

PROBLEM 32

Starting with an alkene, indicate how each of the following compounds can be synthesized:

a. c. e.

b. d. f.

OCH 2 CH 2 CH 3

CH 3 O CH 3

CH 3 CH 2 CHCHCH 3

Br

Br

CH 3 CHOCH 3 CH 2 OH Br CH 3

CH 3

H 2

Pd/C

CH 2 CH 3 CH 3 CH 3 CH 3

or or or

HBr

peroxide

CH 3 CH 3

Br

Cl 2

H 2 O

Cl

OH

Cl 2

CH 3 CH 3

Br

Cl

OH

CC Y+ Z−

YZ

++ C C

reaction of an alkene

an addition reaction

synthesis of an alkene

an elimination reaction