Acylgroepen

Acylgroepen, or acyl groups, are a class of functional groups in organic chemistry characterized by a carbonyl carbon (C=O) that is bonded to another group and to the rest of the molecule. The general structure is R-CO-, where R is typically an alkyl or aryl group. The acyl group is derived from carboxylic acids by removal of the hydroxyl group and represents the acyl portion of molecules that participate in acyl substitution reactions.

Prototypical examples include the acetyl group CH3-CO-, the formyl group H-CO-, and the benzoyl group C6H5-CO-. The acyl group is the defining fragment of a range of derivatives such as esters (R-CO-OR'), amides (R-CO-NR'R''), anhydrides (R-CO-O-CO-R'), acid chlorides (R-CO-Cl) and thioesters (R-CO-SR').

Reactivity: the carbonyl carbon in the acyl group is electrophilic, making acylation and acyl-substitution reactions common. Nucleophiles add to the carbonyl, and a leaving group on the adjacent atom is expelled, converting one acyl derivative to another. In general, acid chlorides and anhydrides are more reactive toward nucleophiles than esters, which are more reactive than amides.

Applications: acyl groups are central to many transformations, including the formation of amides, esters, and anhydrides; Friedel-Crafts acylation applies acyl groups to aromatic rings; acetylation is used to protect alcohols and amines. The term distinguishes the acyl fragment from other carbonyl-containing groups and highlights its role in a wide range of synthetic and mechanistic contexts.