Depto. Química Orgánica

AROMATIC ACYLATION (FRIEDEL-CRAFTS)

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15/07/2017
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If a carbocation is generated from an acyl halyde or an anhydride, the SEAr on benzene leads to an alkyl phenyl ketone.
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The Lewis acid coordinates to the basic centers of the acyl halide or the anhydride and forces the halogen or carboxylate, respectively, to leave giving rise to a carbonyl carbocation whose positive charge is stabilized by the electron lone pairs of the oxygen.
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The carbonyl carbocation is attacked by the aromatic ring, yielding an alkyl phenyl ketone.

IMPORTANT: Carbonyl cations, stabilized by the oxygen, DO NOT  rearrange.

IMPORTANT: The carbonyl group attached to the benzene makes the latter less electron rich and much less reactive thus avoiding polyacylation.
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