ELECTROCHEMISTRY OF 2-THIO-PYRIMIDINES AND 2-OXO-PYRIMIDINES IN DIMETHYL FORMAMIDE IN THE PRESENCE OF DIOXYGEN

Electrocatalysis of dioxygen reduction to superoxide ion in dimethylfo rmamide is afforded by a reversible interaction with thiol or hydroxo forms of pyrimidine which takes place only on the mercury surface elec trode even in the absence of transition metal ions. The interaction is revealed by a polarographic wave and by a voltammetric peak which can be recorded only in the presence of dioxygen in the pyrimidines solut ion. The polarographic wave and voltammetric peak are attributed to th e reduction of the oxygenated pyrimidine. In the range of concentratio n where the polarographic limiting currents due to the reduction of th e oxygenated and unoxygenated pyrimidine are of the same order of magn itude, the stoichiometric ratio dioxygen/pyrimidine is determined to b e 1. The electrode process probably involves the formation of a comple x of mercury with the thiol or the hydroxo form of the pyrimidine on t he electrode surface. Adsorption or coadsorption of the reactants seem s to be involved. (C) 1998 Elsevier Science S.A.