The electrically neutral species H2C: and its derivatives, in which the carbon is covalently bonded to two univalent groups of any kind or a divalent group and bears two nonbonding electrons, which may be spin-paired (singlet state) or spin-non-paired (triplet state). In systematic name formation, carbene is the name of the parent hydride :CH2 ; hence, the name dichlorocarbene for :CCl2. However, names for acyclic and cyclic hydrocarbons containing one or more divalent carbon atoms are derived from the name of the corresponding all-![[lambda]](/img5/l_files/LAMBDA.gif)
4-hydrocarbon using the suffix -ylidene. RNRI Rule RC-81.1.3. NOC Rule C-81.1. E.g. CH 2=CHCH: prop-2-en-1-ylidene; 
cyclohexylidene, H2C=C: ethenylidene.
Subclasses of carbenes include acyl carbenes RC(=O)C:R, imidoyl carbenes, RC(=NR)C:R, and vinyl carbenes.
