Polarographic study of bis(2-pyridyl)disulphide di- N-oxide and bis(2-quinolyl)disulphide di- N-oxide in aqueous ethanol

Abstract

The polarographic reduction of bis(2-pyridyl)- and of bis(2-quinolyl)disulphide di- N-oxide in aqueous alcohol yields aryl mercaptans. The electrode reaction is kinetically controlled by an initial one-electron transfer step, and values for the transfer coefficients and the specific heterogeneous rate constants for the forward reactions are presented. The polar N-oxide function in the α-position withdraws electrons from the disulphide bond, making the half-wave potential less negative than that of the diphenyl disulphide. The p k a values of the mercapto compounds formed have been evaluated and the low values obtained for the heterocyclic N-oxides are further evidence for tautomerism in these compounds.