FriedelCraftstype

FriedelCraftstype refers to reactions of the Friedel-Crafts type in organic chemistry, a class of electrophilic aromatic substitutions used to substitute hydrogen on an aromatic ring with alkyl or acyl groups. The term encompasses the main Friedel-Crafts variants, notably Friedel-Crafts alkylation and Friedel-Crafts acylation, typically carried out in the presence of a Lewis acid catalyst such as aluminum chloride or ferric chloride.

Historically, these reactions were developed in the late 19th century by Charles Friedel and James Crafts and have since become fundamental tools for constructing substituted arenes. The underlying mechanism involves generation of a strong electrophile, such as a carbocation from an alkyl halide or an acylium ion from an acyl chloride, which then attacks the π system of benzene or another activated aromatic ring. Deprotonation restores the aromatic system and yields the substituted product.

FriedelCraftstype encompasses two principal variants. Friedel-Crafts alkylation introduces an alkyl group but can suffer from polyalkylation and carbocation rearrangements, which limit selectivity with some substrates. Friedel-Crafts acylation forms aryl ketones and is generally more controlled: the acyl group is deactivating and meta-directing for subsequent substitutions, and rearrangements do not occur.

Limitations include the need for anhydrous, strongly Lewis-basic conditions, sensitivity to water, and restricted use with deactivated rings. Modern practice often favors acylation for reliable selectivity, while alkylation is used with careful substrate choice and protective strategies.