An acyl group (IUPAC name: alkanoyl) is a functional group derived by the removal of one or more hydroxyl groups from an oxoacid.Compendium of Chemical Terminology, acyl groups In organic chemistry, the acyl group is usually derived from a carboxylic acid. It therefore has the formula RCO, where R represents an alkyl group that's attached to the CO group with a single bond. Although the term is almost always applied to organic compounds, acyl groups can in principle be derived from other types o… (More on Acyl)