Methine group

In organic chemistry, a methine group or methine bridge is a trivalent functional group =CH−, derived formally from methane.

The group is also called methyne or methene, but its IUPAC systematic name is methylylidene or methanylylidene.

The name "methine" is also widely used in non-systematic nomenclature for the methanetriyl group (IUPAC): a carbon atom with four single bonds, where one bond is to a hydrogen atom (>CH−).

Chains of alternating single and double bonds often form conjugated systems.

When closed, as in benzene (=CH−CH=)3, they often give aromatic character to the compound.