Methine group
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In chemistry, methine (also known as methylidyne or methyne) is a tri-valent functional group CH, derived formally from methane. The methine group consists of a carbon atom bound by two single bonds and one double bond, where one of the single bonds is to a hydrogen. This can also encompass subunits of an aromatic compound, although these do not have discrete single and double bonds.
It is sometimes used non-systematically for a carbon with four single bonds, where one bond is to a hydrogen.
Example
Every carbon in this molecule is a methyne carbon, except the two attached to the two nitrogens and that are not attached to any hydrogens, and the one attached to the nitrogen, which is attached to two hydrogens (far right). There is a five-carbon poly-methyne chain in the center of this molecule.