Return to Contents  Chapter 17: Aldehydes and Ketones. Nucleophilic Additionto C=O  Ch 17 contents

Friedel-Crafts Acylation of Benzene
(review of Chapter 12)

acylation of arenes

Reaction type: Electrophilic Aromatic Substitution

Summary.

MECHANISM FOR THE FRIEDEL-CRAFTS ACYLATION OF BENZENE
Step 1:
The acyl halide reacts with the Lewis acid to form a a more electrophilicC, an acylium ion
Friedel-Crafts acylation of benzene
Step 2:
The π electrons of the aromatic C=Cact as a nucleophile, attacking the electrophilic C+. This step destroysthe aromaticity giving the cyclohexadienyl cation intermediate.
Step 3:
Removal of the proton from the sp3 C bearing the acyl- groupreforms the C=C and the aromatic system, generating HCl and regeneratingthe active catalyst.

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© Dr. Ian Hunt, Department of Chemistry, University of Calgary