acyl group

A general acyl group (blue) in a ketone (top left), as an acylium cation (top centre), as an acyl radical (top right), an aldehyde (bottom left), ester (bottom centre) or amide (bottom right). ( R, R and R stands for organyl substituent or hydrogen in the case of R)

In chemistry, an acyl group is a moiety derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids. It contains a double-bonded oxygen atom and an organyl group (R−C=O) or hydrogen in the case of formyl group (H−C=O). In organic chemistry, the acyl group (IUPAC name alkanoyl if the organyl group is alkyl) 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. Although the term is almost always applied to organic compounds, acyl groups can in principle be derived from other types of acids such as sulfonic acids and phosphonic acids. In the most common arrangement, acyl groups are attached to a larger molecular fragment, in which case the carbon and oxygen atoms are linked by a double bond.