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.
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 group name
|Corresponding carboxylic acid name|
|formyl||methanoyl||formic acid||methanoic acid|
|acetyl||ethanoyl||acetic acid||ethanoic acid|
|propionyl||propanoyl||propionic acid||propanoic acid|
|acryl||propenoyl||acrylic acid||propenoic acid|
In acyloxy groups the acyl group is bonded to oxygen: R-C=O-O-R' where R-C=O is the acyl group.