Title: carbenes
Long Title: IUPAC Gold Book - carbenes
DOI: 10.1351/goldbook.C00806
Status: current

Definition
The electrically neutral species $\ce{H2C{:}}$ (methylene) 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 $\ce{C{:}H2}$ hence, the name dichlorocarbene for $\ce{C{:}Cl2}$. However, names for acyclic and cyclic hydrocarbons 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, $\ce{H2C=CHCH{:}}$ ethenylidene, $\ce{H2C=C{:}}$; cyclohexylidene,Subclasses of carbenes include acyl carbenes , imidoyl carbenes,  and vinyl carbenes.

Related Terms
- acyl carbenes: https://goldbook.iupac.org//terms/view/A00121
- hydrocarbons: https://goldbook.iupac.org//terms/view/H02889
- imidoyl carbenes: https://goldbook.iupac.org//terms/view/I02953
- parent hydride: https://goldbook.iupac.org//terms/view/P04405
- singlet state: https://goldbook.iupac.org//terms/view/S05699
- systematic name: https://goldbook.iupac.org//terms/view/S06236
- triplet state: https://goldbook.iupac.org//terms/view/T06503
- vinyl carbenes: https://goldbook.iupac.org//terms/view/V06620

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)

Related Reference
- PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1092 (https://doi.org/10.1351/pac199466051077)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/C00806/html
- json: https://goldbook.iupac.org/terms/view/C00806/json
- xml: https://goldbook.iupac.org/terms/view/C00806/xml

Citation: Citation: 'carbenes' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.C00806
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Accessed: 2026-05-18T02:54:06+00:00