Investigation of photolysis of o-nitrophenols by electron spin resonance spectroscopy. Characterisation of 1,2-benzoquinone monohydroxyimine free radicals

Abstract

The photolysis of tetrahydrofuran (THF) solutions containing o-nitrophenols and di-t-butyl peroxide (DTBP) has been examined by e.s.r. spectroscopy. In carefully degassed solutions a series of 1,2-benzoquinone monohydroxyimine free radicals are formed, the structures of which have been confirmed using an unambiguous synthesis by oxidation of appropriate nitrosophenols in a flow system. The origin of hyperfine splittings is such radicals has been evaluated. Structures are tentatively proposed for free radicals observed during the photolysis of inefficiently degassed THF solutions of o-nitrophenols and DTBP; the same radicals are obtained when analogous nitrosophenols are photolysed under identical conditions.