Atomic carbon

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Atomic carbon
Identifiers
PubChem 5462310
ChemSpider 4575370 YesY
ChEBI CHEBI:27594 YesY
Jmol-3D images Image 1
Properties
Molecular formula C
Molar mass 12.01 g mol−1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Atomic carbon (systematically named λ0-methane and carbon), also called monocarbon, is an inorganic chemical with the chemical formula C. It is a colorless gas that only persists at elevated temperatures or indefinitely in dilution. It is classified as a very strong acid; atomic carbon is highly corrosive.

Nomenclature[edit]

The trivial name monocarbon is the preferred IUPAC name. The systematic names, λ0-methane and carbon, valid IUPAC names, are constructed according to the substitutive and additive nomenclatures, respectively.

In appropriate contexts, atomic carbon can be viewed as methane with all hydrogen atoms removed, and as such, methanediylidene may be used as a context-specific systematic name, according to substitutive nomenclature. By default, this name pays no regard to the radicality of the atomic carbon. Although, in even more specific context, it can also name the non-radical excited states, whereas the diradical ground state is named methanediylylidene.

Chemical properties[edit]

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 diazo compounds, might exhibit properties better attributed to the diazo compound 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.

Amphotericity[edit]

Atomic carbon can accept or donate a pair of electrons into or from the atom, respectively, by adduction:

C + R → CR

Because of this accepting and donating of the electron pair, atomic carbon has Lewis-amphoteric character. Atomic carbon can accept or donate two pairs of electrons.

A hydroxyl centre can also be assimilated into the atom by ionisation:

C + OH
CO
+ H

or...

C + OH
CHO

Because of this capture of a hydroxide (OH
), atomic carbon has Arrhenius-acidic character. Atomic carbon can capture two hydroxides. Atomic carbon does not form stable aqueous solutions due to hydration.

C + 2 H
2
O
→ CHO(OH) + 2 H

or...

C + 2 H
2
O
CH
2
(OH)
2

Production[edit]

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.

This very short lived species is created by passing a large current through two adjacent carbon rods, generating an electric arc. Atomic carbon is generated in the process. Professor Phil Shevlin has done the principal 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.

References[edit]

  • White G. J., Padman R. (1991). "Images of atomic carbon in the interstellar medium". Nature 354 (6354): 511–513. Bibcode:1991Natur.354..511W. doi:10.1038/354511a0. 
  • P. B. Shevlin (1972). "Formation of Atomic Carbon in the Decomposition of 5-tetrazoyldiazonium Chloride". J. Amer. Chem. Soc. 94 (4): 1379. doi:10.1021/ja00759a069. 
  • P. B. Shevlin (1980). "The Preparation and Reaction of Atomic Carbon". In R. A. Abramovitch. Reactive Intermediates, 1. New York: Plenum Press. 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 (10): 2802. doi:10.1021/ja00400a052. 
  • Biesiada, Keith A.; Shevlin, Philip B. (1984). "Intramolecular trapping of an intermediate in the deoxygenation of a carbonyl compound by atomic carbon". The Journal of Organic Chemistry 49 (6): 1151. doi:10.1021/jo00180a047. 
  • Moss, Robert A; Jones, Maitland (2004). "Atomic carbon". Reactive intermediate chemistry. pp. 463–500. ISBN 978-0-471-23324-4.