The functionalization of saturated hydrocarbons .35. on the intermediates in an Fe-III catalase model in pyridine. Relevance to the catalase enzyme.

Ferric chloride in pyridine behaves as an efficient model for the catalase enzyme. It converts H2O2 nearly quantitatively into water and oxygen (2 H2O2 --> 2 H2O + O-2) The addition of Ph(2)S to the model system affords Ph(2)SO, the amount which increases with the Ph(2)S added. The inverse relationship between oxygen and Ph(2)SO formation proves that there is an intermediate in the model catalase reaction. When di-n-butyl, di-t-butyl and diphenyl sulfides are reacted in pairs in competition for the intermediate a large steric effect of over 600 is found for the di-n-butyl versus dit-butyl sulfoxide formation. In contrast the same number for per-acid oxidation is 8. It is concluded from this and other evidence that the intermediate is and Fe-V oxenoid, or equivalent, which reacts competitively with H2O2 to give oxygen and with sulfides to furnish sulfoxides. Comparison is made with the catalase enzyme in water and in water-acetonitrile. An unexpected by-product of this study is an efficient and economic procedure for the oxidation of sulfides to sulfoxides without further significant oxidation to sulfones. Copyright (C) 1996 Elsevier Science Ltd