An acyl group is a functional group found in organic compounds. It is a moiety derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids. The general formula for an acyl functional group is RCO-, where R is bound to the carbon atom with a single bond. In organic chemistry, the acyl group is usually derived from a carboxylic acid, in which case it has the formula R−C(=O)−, where R represents an organyl group or hydrogen. Acyl groups can also be derived from other types of acids such as sulfonic acids and phosphonic acids. Acyl groups are thioesters when they are acyl derivatives formed via fatty acid metabolism.
Some examples of acyl groups include acetyl group, benzoyl group, and alkanoyl group. The acetyl group is derived from acetic acid and has the formula CH3CO- . The benzoyl group is derived from benzoic acid and has the formula C6H5CO- . The alkanoyl group is derived from an alkanoic acid and has the formula RCO- .
Acylium ions are cations of the type R−C+=O ↔ R−C≡O+ and play an important role as intermediates in organic reactions. Acyl groups of amino acids are formed by replacing the -ine suffix with -yl. For example, the acyl group of glycine is glycyl, and of lysine is lysyl.
