A phosphoryl group is the chemical entity PO₃^2-. It may exist in different protonation states. The term is usually used to refer to compounds in which the phosphoryl group is attached to other atoms, e.g. phosphoryl chloride, or in the description of catalytic mechanisms. In biochemical reactions involving phosphates (e.g. Adenosine triphosphate), a phosphoryl group is usually transferred between the substrates (phosphoryl transfer reactions). A phosphoryl group should not be confused with a phosphate group.