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 R₁ or R₂ = OH, esters, in which R₁ or R₂ = OR, and amides, in which R₁ or R₂ = N(R₃)R₄. The chemical weapon phosgene is a carbonyl group with R₁=R₂=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.