Semiquinone free radicals and oxygen. Pulse radiolysis study of one electron transfer equilibria

Abstract

The absorption characteristics and acid dissociation constants of the semiquinone radicals of several methyl derivatives of benzoquinone and naphthoquinone have been determined by pulse radiolysis.Absolute rate constants for electron transfer from the superoxide-ion O–2 to mono- and di-methyl benzoquinones have been determined. In the case of duroquinone, evidence has been obtained for the occurrence of the equilibrium reaction: O–2+ duroquinone ⇌ O2+ durosemiquinone with Kc= 2.3 ± 0.2 × 10–2.