Free Radical Terminology

Abstract

SOME confusion appears to be creeping into the literature with regard to the designation of molecules which function as free radicals. Some authors, for example, describe methylene H₂C = as a diradical, and the next step presumably will be to term methine HC= a triradical. This is certain to lead to confusion, since methylene contains a carbon atom with an electron sextet, while a diradical, such as–CR₂–CR₂–CR₂–, contains two carbon atoms with an electron septet or free valence. Accordingly, methylene with its electron sextet should be regarded as a bivalent radical. It is true that oxygen, in virtue of its high paramagnetism, is considered to be a diradical, but this refers to the oxygen molecule,–O–O–, with each atom carrying a free valence.