Friedel–Crafts acylation of benzene with acetyl chloride in AlCl3 gives which ketone?

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Multiple Choice

Friedel–Crafts acylation of benzene with acetyl chloride in AlCl3 gives which ketone?

Friedel–Crafts acylation uses an acylium ion as the electrophile. Here, acetyl chloride with a Lewis acid forms the acylium ion CH3–CO+. This electrophile attacks benzene to form a sigma complex, which upon deprotonation gives the aryl ketone with the acyl group attached directly to the ring. The result is acetophenone (Ph–CO–CH3). This outcome is distinct from benzophenone (which would require a benzoyl cation to attach a second phenyl group) or benzaldehyde (which would involve inserting a formyl group rather than an acetyl group). The acetyl group adds as a carbonyl-bearing substituent, yielding the ketone shown.

Friedel–Crafts acylation uses an acylium ion as the electrophile. Here, acetyl chloride with a Lewis acid forms the acylium ion CH3–CO+. This electrophile attacks benzene to form a sigma complex, which upon deprotonation gives the aryl ketone with the acyl group attached directly to the ring. The result is acetophenone (Ph–CO–CH3).

This outcome is distinct from benzophenone (which would require a benzoyl cation to attach a second phenyl group) or benzaldehyde (which would involve inserting a formyl group rather than an acetyl group). The acetyl group adds as a carbonyl-bearing substituent, yielding the ketone shown.

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