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 (@S05699@) or spin-non-paired (@T06503@). In @S06236@ formation, carbene is the name of the @P04405@ :CH2 hence, the name dichlorocarbene for :CCl2. However, names for acyclic and cyclic @H02889@ containing one or more divalent carbon atoms are derived from the name of the corresponding all-\(\lambda ^{4}\)-hydrocarbon using the suffix -ylidene. E.g. prop-2-en-1-ylidene, H2C=CHCH: ethenylidene, H2C=C:; cyclohexylidene,

Subclasses of carbenes include @A00121@ C00806-2.png, @I02953@, C00806-3.png and @V06620@.
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1324 [Terms] [Paper]
See also:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1092 [Terms] [Paper]