Electron transfer (oxidation) of complexes between bifunctional phenols and DMSO in non-polar surroundings

Pulse-radiolysis reactions were performed to study the effect of hydrogen bonding to dimethyl sulfoxide (DMSO) on the oxidation of dihydroxy benzene and biphenyl diols to phenoxyl radicals. It was observed that with DMSO as the hydrogen-bond acceptor, the oxidation process proceeds via proton-coupled electron transfer in the case of hydroquinone. For resorcinol, DMSO acts in a similar way as in the case of hydroquinone. For other biphenols, viz., 2,2′- and 4,4′-biphenyl diols, it was found that DMSO had no effect on the electron transfer. The results are explained based on the ionization potential and structure of the phenol derivatives which probably depends on the rotation of the OH bond causing different electron distribution in the transient conformation.