Formation of stable aryldisulphide ions in dimethylacetamide from the reaction of sulphur with thiolate ions

Abstract

The conditions for the formation of aryldisulphide ions, RS₂^– during the direct reaction of sulphur with thiolate ions RS^– have been studied by the use of spectroelectrochemistry in dimethylacetamide. The series of derivatives examined was R =p-tolyl (1), phenyl (2), 8-quinolyl (3), 2- and 4-pyridyl (4), (5), N-oxido 4-pyridyl (6), 2- and 4-nitrophenyl (7), (8), and 2-(5-nitropyridyl)(9). Sulphur reaction leads to RS₂^– ions and precedes the oxidation to diaryldisulphide RS₂R and polysulphide ions S_x^2–. With derivatives (1)–(3), both reactions are successive and practically stoicheiometric, while for derivatives containing electron-withdrawing groups (6)–(9), the equilibrium constants have been measured. Analysis of the reaction products by methylation of several solutions of thiolate ions [(2), (7), (8)] in the presence of sulphur confirmed the possibility of obtaining aryldisulphide ions stabilized in aprotic dipolar media.