Also found in: Dictionary, Wikipedia.



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 ?
They eventually turned to carbenes to create a gold-carbon bond, which succeeded beyond all expectations.
Carbenes usually exist only fleetingly in reactions that produce substances ranging from polymers to drugs.
Among the topics are enantioselective annulations with chiral N-mesityl N-heterocyclic carbenes, the construction of anti-Me-OH vicinal relationships in polyketides, asymmetric catalysis in the total synthesis of lipids and polyketides, hetercycle construction via asymmetric rhodium-catalyzed cylcoadditions, and dynamic kinetic asymmetric transformations involving carbon-carbon bond cleavage.
Catalytically active metal complexes derived from N-heterocyclic carbenes (NHC) have found increasing interest in the last years, in part due to the unique electronic and steric properties of the ligands.
The original discovery was made by accident two years ago while studying the bonding properties of rhodium complexes of N-heterocyclic carbenes (NHCs).
Rovia I Virgili, Spain), presents 15 papers demonstrating some of these applications, covering transformations such as hydrogenation, hydroamination, hydroboration, C--C bond formation, carbonylation, and cyloadditions, as well as recent catalytic system using iridium nanoparticles and the use of relevant ligands as carbenes and pincer ligands.
The scientists made carbon dioxide react by using N-heterocyclic carbenes (NHCs), a novel organocatalyst.
in organic chemistry from Rutgers University and has several patents in the areas of carbenes, coatings and polymers.
Asphalts are generally constituted of an oily phase composed of saturated hydrocarbons (paraffinics and maltenes), cyclic products (naphthenes and aromatics) and resins (polar aromatics); and a non-oily phase composed of asphaltenes, carbenes, etc.
Chelating carbenes and their ability to block access to a metal center could prove to be useful for catalytic functions.
He describes quantum mechanics for organic chemistry, fundamentals of organic chemistry, pericyclic reactions, diradicals and carbenes, organic reactions of anions, solution-phase organic chemistry, and organic reaction dynamics, all of which he punctuates with personal interviews with leading lights in the field.