Letter | Published:

Some Chemical Reactions of Sulphur Hexafluoride

Naturevolume 193page473 (1962) | Download Citation



SULPHUR hexafluoride has customarily been considered to be chemically inert. It is unaffected by aqueous or fused alkali, ammonia or oxygen. The earliest report1 states that sulphur hexafluoride is reductively degraded by sulphur and selenium, vapours, and hydrogen sulphide at elevated temperatures, but these reactions have never been reinvestigated. The only substantiated chemical reaction of sulphur hexafluoride is that with a hot alkali metal, reaction with a film of sodium commencing at 200° 2. The great stability of sulphur hexafluoride is kinetic rather than thermodynamic in origin since it is thermodynamically unstable with respect to water3. The inability of nucleophilic reagents to attack the sulphur hexafluoride molecule can be ascribed to their failure to form an SN2 type transition state because the sulphur atom has no orbital of sufficiently low energy to permit its coordination with the unshared electron pair of the entering nucleophile. Attack by a nucleophilic reagent on a fluorine atom of sulphur hexafluoride is improbable for the same reason. However, there still remains the possibility of reaction with an electrophilic reagent, for example, a strong Lewis acid, the transition state of which is formed by co-ordination of the reagent with a fluorine atom using one of its lone electron pairs. This possibility does not appear to have been investigated until now.

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  1. 1

    Moissan, H., and Lebeau, P., C.R. Acad. Sci., Paris, 130, 869 (1900).

  2. 2

    Cowen, H. C., Riding, F., and Warhurst, E., J. Chem. Soc., 4168 (1953).

  3. 3

    Roberts, H. L., Quart. Rev. Chem. Soc., 15, 30 (1961).

  4. 4

    Gross, P., Hayman, C., and Levi, D. L., Intern. Symp. Fluorine Chemistry, Birmingham (1959).

  5. 5

    National Bureau of Standards, Circ. 500.

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  1. Imperial Chemical Industries, Ltd., Research Department, Alkali Division, Northwich, Cheshire

    • J. R. CASE
    •  & F. NYMAN


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