Term: carbenes
https://doi.org/10.1351/goldbook.C00806

Definition:
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,C00806-1.pngSubclasses of carbenes include acyl carbenes C00806-2.png, imidoyl carbenes, C00806-3.png and vinyl carbenes.

Related Terms:
1) singlet state (http://doi.org/10.1351/goldbook.S05699).
2) triplet state (http://doi.org/10.1351/goldbook.T06503).
3) systematic name (http://doi.org/10.1351/goldbook.S06236).
4) parent hydride (http://doi.org/10.1351/goldbook.P04405).
5) hydrocarbons (http://doi.org/10.1351/goldbook.H02889).
6) acyl carbenes (http://doi.org/10.1351/goldbook.A00121).
7) imidoyl carbenes (http://doi.org/10.1351/goldbook.I02953).
8) vinyl carbenes (http://doi.org/10.1351/goldbook.V06620).

Images:
1) cyclohexylidene (carbene) (https://goldbook.iupac.org/img/inline/C00806-1.png) 
2) generic acyl carbene (https://goldbook.iupac.org/img/inline/C00806-2.png) 
3) generic imidoyl carbene (https://goldbook.iupac.org/img/inline/C00806-3.png) 

Source: PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1324 (https://doi.org/10.1351/pac199567081307)

Citation: 'carbenes' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.C00806

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