Atomic carbon

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Making atomic carbon :C: - The source of light is the electrical arcing between two carbon rods. Liquid nitrogen cools the reaction vessel. The black substance is soot. This photo was taken in the Laboratory of Professor Phil Shevlin at Auburn University.

Atomic carbon in chemistry is single carbon atom with chemical formula :C: - in effect a dicarbene.

The species is very short lived species and is created by passing a large current through two adjacent carbon rods which generates an electric arc. Atomic carbon is generated in the process. Professor Phil Shevlin has done the principle work in the field based at Auburn University in the USA.

The way this species is made is closely related to the formation of fullerenes C60, the chief difference being that a much lower vacuum is used in atomic carbon formation.

This species has been used to generate "true" carbenes by the abstraction of oxygen atoms from carbonyl groups:

R₂C=O + :C: → R₂C: + CO

Carbenes formed in this way will exhibit true carbenic behaviour. Carbenes prepared by other methods such as diazocompounds, might exhibit properties better attributed to the diazocompound used to make the carbene (which mimic carbene behaviour), rather than to the carbene itself. This is important from a mechanistic understanding of true carbene behaviour perspective.

[edit] References

• White G. J., Padman R. (1991). "Images of atomic carbon in the interstellar medium". Nature 354: 511 - 513. DOI:10.1038/354511a0. 

• P. B. Shevlin (1972). "Formation of Atomic Carbon in the Decomposition of 5-tetrazoyldiazonium Chloride". J. Amer. Chem. Soc. 94: 1397. DOI:10.1021/ja00759a069. 

• P. B. Shevlin, "The Preparation and Reaction of Atomic Carbon" in Reactive Intermediates, Vol. 1 R. A. Abramovitch Ed. Plenum Press. New York, 1980, p. 1.

• M. J. S. Dewar, D. J. Nelson, P. B. Shevlin, K. A. Biesida (1981). "An Experimental and Theoretical Investigation of the Mechanism of Deoxygenation of Carbonyl Compounds by Atomic Carbon". J. Amer. Chem. Soc. 103: 2802. DOI:10.1021/ja00400a052. 

• K. A. Biesiada and P. B. Shevlin "The Intramolecular Trapping of an Intermediate in the Deoxygenation of a Carbonyl Compound by Atomic Carbon" J. Org. Chem. 1984, 49, 1151. DOI:10.1021/jo00180a047

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