Page 168 - Pharm.Org.Chem I 05-PC101 (1)

Limitations to Friedel-Crafts alkylation

• Rearrangement to more stable carbocations.
• Poly alkylation.
• Electron withdrawing groups on benzene ring hinder

F.C. reactions
Examples: NO2, COOH, COR, CF3, SO3H.
Remember: vinyl chloride or chlorobenzene can’t be
used as alkyl halides in F.C. alkylation as they don’t form
carbocations.

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Friedel-Crafts Acylation

• With the same concept, Friedel-Crafts acylation introduces an acyl RC=O
group to the benzene ring, by reacting benzene with acyl chloride in presence
of AlCl 3 as catalyst to yield acylbenzene which is in fact a ketone.

Overall
reaction

• This acyl benzene could serve as a source of introducting 1 o alkyl chain by
reduction using Zn/ Hg / HCl.

2025-026 Dr. Marwa El-Wakil Clemmensen
reduction

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