Acyl

Overview
An acyl group (IUPAC name: alkanoyl) is a functional group derived by the removal of one or more hydroxyl group from an oxoacid. . In organic chemistry, the acyl group is usually derived from a carboxylic acid of the form RC O OH. It therefore has the formula RC(=O)-, with a double bond between the carbon and oxygen atoms (i.e. a carbonyl group), and a single bond between R and the carbon. Acyl groups can also be derived from other types of acids such as sulfonic acids, phosphonic acids, and some others.

Acyl halides can be used in Friedel-Crafts acylation to introduce the acyl moiety in an aromatic compound.

In biochemistry, Acyl-CoA is a derivate of fatty acid metabolism.

Examples
The names of acyl groups are typically derived from the corresponding acid by substituting the acid ending -ic with the ending -yl as shown in the table below. Note that methyl, ethyl, propyl, butyl etc. end in -yl are not acyl but alkyl groups, derived from alkanes.

Acyl species
In acyloxy groups the acyl group is bonded to oxygen: R-C=O-O-R' where R-C=O is the acyl group.

Acylium ions are cations of the type R-C+=O and play an important role as intermediates in organic reactions for example the Hayashi rearrangement.