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unstable organic compounds containing an electrically neutral divalent carbon atom R’R“C: (the dots denote two electrons); they are intermediate particles in many organic reactions. The simplest carbene, methylene, :CH2, is formed in thermal or photochemical dissociation of diazomethane or ke-tene:

CH2N2→:CH2 + No

Other carbenes may be produced analogously. Dihalocarbenes form during thermal dissociation of alkali salts of trihaloacetic acids:

CCl3COONa → :CC12 + NaCl + CO2

Various methods are used for stabilizing carbenes, depending on the conditions of generation and the nature of the compounds interacting with the carbenes. For example, the following can occur: (1) dimerization of carbenes, :CH2 + :CH 2→CH2═CH2; (2) intrusion of carbenes through the carbon-hydrogen bond (for example, into hydrocarbons), R−H + :CH2 → R− CH3; or (3) combination of carbenes by a multiple bond (for example, ethylene), with the formation of a three-member ring,

The last reaction is widely used in the synthesis of various three-member cyclic compounds.


Knuniants, I. L., N. P. Gambarian, and E. M. Rokhlin. “Karbeny.” Uspekhi khimii, 1958, vol. 27, issue 12, p. 1361.


References in periodicals archive ?
With the help of some talented graduate students and postdoctoral fellows, that inquiry made a key distinction between the role of N-heterocyclic carbene (NHC) and phosphine (PH3), which many observers had thought were equivalent participants in the cross-coupling.
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