Friedel–Crafts reaction

A class of electrophilic aromatic substitution reactions that installs alkyl or acyl groups on aromatic rings, typically using a Lewis acid catalyst.

Electrophilic aromatic substitution: A reaction in which an electrophile replaces a hydrogen atom on an aromatic ring while aromaticity is restored. Friedel–Crafts alkylation and acylation are members of this reaction family.
Aromaticity: The unusual stability of a cyclic, conjugated molecule with a delocalized electron system meeting aromaticity criteria. The ring temporarily loses aromaticity during substitution, then regains it when a proton is removed.
Friedel–Crafts alkylation: An electrophilic aromatic substitution that adds an alkyl group to an aromatic ring. Unlike acylation, it can cause carbocation rearrangement and repeated substitution.
Acetophenone: An aromatic ketone with a phenyl group bonded to a carbonyl methyl group. Benzene acylation with an acetylating reagent is a standard route to this product.
Charles Friedel: A French chemist whose research included organosilicon compounds and reactions catalyzed by aluminum chloride. He co-discovered the reaction named for him and James Mason Crafts.
Acylium ion: A resonance-stabilized cation with the general structure RCO⁺. This electrophile commonly transfers the acyl group during acylation.
Benzene: A six-carbon aromatic hydrocarbon with a planar ring of delocalized pi electrons. Benzene is the simplest common substrate for illustrating both reaction types.
Friedel–Crafts acylation: An electrophilic aromatic substitution that adds an acyl group to an aromatic ring. Its electrophile does not rearrange, and the product carbonyl deactivates the ring against further acylation.
Toluene: An aromatic hydrocarbon consisting of a benzene ring bonded to a methyl group. Benzene alkylation with a methyl electrophile produces toluene.
James Mason Crafts: An American chemist known for research on aromatic compounds and aluminum chloride-catalyzed reactions. His collaboration with Charles Friedel established the reaction in 1877.

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