Carbonyl group

A carbonyl group is a functional group which consists of a carbon atom with is double bound to an oxygen atom. Closely related chemical groups include carboxylic acids, in which R or R' = OH, esters, in which R or R' = OR", and amides, in which R or R' = N(R3)R4. The chemical weapon phosgene is a carbonyl group with R=R'=Cl.

Carbonyl groups are polar and the carbon atom is electrophilic. As such, nucleophilic attack of the carbon atom is a useful reaction mechanism for chemicals containing a carbonyl group.