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Also known as: FC Alkylation
Discovered by Charles Friedel, James Crafts (1877)
Lewis acid-catalyzed electrophilic aromatic substitution where an alkyl group is introduced onto the aromatic ring. AlCl₃ generates a carbocation (or carbocation-like) electrophile from the alkyl halide.
AlCl₃ coordinates with the alkyl halide, generating a carbocation (or a highly polarized complex that acts like one).
3° halides form free carbocations; 1° form polarized complexes
The electrophilic carbocation attacks the aromatic ring, forming the arenium ion (sigma complex).
Deprotonation restores aromaticity, giving the alkylated arene product.
Benzene + CH₃Cl
AlCl₃
Toluene (+ polyalkylation products)
Benzene + (CH₃)₂C=CH₂
AlCl₃ or H₃PO₄
tert-Butylbenzene
Introduces alkyl groups onto aromatic rings. Limited by polyalkylation and rearrangements — FC acylation is usually preferred.