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-λ4-hydrocarbon using the suffix -ylidene. E.g. prop-2-en-1-ylidene, H2C=CHCH: ethenylidene, H2C=C:; cyclohexylidene,

Subclasses of carbenes include acyl carbenes C00806-2.png, imidoyl carbenes, C00806-3.png and vinyl carbenes.
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1324 (
See also:
PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1092 (