acylgroup

An acyl group is a functional group in organic chemistry defined as RC(O)-, where R is an alkyl, aryl, or other substituent. It is derived from a carboxylic acid by removal of the hydroxyl group. The carbonyl carbon is sp2-hybridized and the group is typically planar. When R is hydrogen, the acyl group is the formyl group (H-CO-).

In chemical reactions, acyl groups are electrophilic at the carbonyl carbon and undergo nucleophilic acyl substitution. They occur in a wide family of derivatives, including acid chlorides (R-COCl), anhydrides (R-CO-O-CO-R'), esters (R-COOR'), and amides (R-CO-NR'R''). These transformations are central to forming and interconverting carboxyl derivatives, enabling installation of the acyl group onto alcohols, amines, and other nucleophiles.

Common acyl groups include acetyl (CH3-CO-), benzoyl (C6H5-CO-), and formyl (H-CO-). Biologically, acyl groups are important in metabolism and regulation, as seen in acetyl transfer reactions involving acetyl-CoA and in protein acetylation. In synthetic chemistry, acyl groups are used to protect or modify functional groups, to form esters and amides, and to enable various acylation strategies, including electrophilic aromatic acylation and acyl transfers under catalysis.