Organic Chemistry

James Mason Crafts (1839–1917)
was born in Boston, the son a of
woolen-goods manufacturer. He
graduated from Harvard in 1858
and was a professor of chemistry at
Cornell University and the Massa-
chusetts Institute of Technology. He
was president of MIT from 1897 to
1900, when he was forced to retire
because of chronic poor health.

Charles Friedel (1832–1899)was
born in Strasbourg, France. He was a
professor of chemistry and director of
research at the Sorbonne. At one
point, his interest in mineralogy led
him to attempt to make synthetic
diamonds. He met James Crafts when
they both were doing research at
L’Ecole de Médicine in Paris.
They collaborated scientifically for
most of their lives, discovering the
Friedel–Crafts reactions in Friedel’s
laboratory in 1877.

612 CHAPTER 15 Aromaticity • Reactions of Benzene

15.13 Friedel–Crafts Acylation of Benzene

Two electrophilic substitution reactions bear the names of chemists Charles Friedel

and James Crafts. Friedel–Crafts acylationplaces an acyl group on a benzene ring,

and Friedel–Crafts alkylationplaces an alkyl group on a benzene ring.

Either an acyl halide or an acid anhydride can be used for Friedel–Crafts acylation.

An acylium ion is the electrophile required for a Friedel–Crafts acylation reaction.

This ion is formed by the reaction of an acyl chloride or an acid anhydride with

a Lewis acid.

Because the product of a Friedel–Crafts acylation reaction contains a carbonyl

group that can complex with Friedel–Crafts acylation reactions must be carried

out with more than one equivalent of When the reaction is over, water is added

to the reaction mixture to liberate the product from the complex.

PROBLEM 20

Show the mechanism for the generation of the acylium ion if an acid anhydride is used in-

stead of an acyl chloride in a Friedel–Crafts acylation reaction.

AlCl 3.

AlCl 3 ,

mechanism for Friedel–Crafts acylation

O

CAlCl 3 −AlCl 4

R Cl

C

C

O

B

O

H

R

C

O

R R

+

+

+

+ HB+

+

+

R CO+

R CO+

an acylium ion

AlCl 3 ,

++HCl

1. AlCl 3


2. H 2 O

Friedel–Crafts acylation

O

C

R

R

an acyl chloride

+ +

1. AlCl 3


2. H 2 O

O

C

an acid anhydride

O

C

O

O

C

R

R

O

C

Cl

R

O

C

R OH

O

C

an acyl group

R

an alkyl group

R

O

C

RRR+

+ −

AlCl 3 + Al(OH) 3 + 3 HCl

3 H 2 O

O

C

O

C

AlCl 3