A chemical moiety consisting of O with a double bond to C. If the C is bonded to N, the resulting structure is termed an amide; if it is bonded to O, it is termed a carboxylic acid or an ester linkage.
carbonyl group. divalent group consisting of a carbon atom with a double-bond to oxygen. For example, acetone (CH3-(C=O)-CH3) is a carbonyl group linking two methyl groups. Also refers to a compound of a metal with carbon monoxide, such as iron carbonyl, Fe(CO)5.