Reduction potentials of thiuram disulfide/dithiocarbamate couples in acetone/water

Abstract

Reduction potentials relative to the saturated calomel electrode, Eº, of a series of thiuram disulfide/ dithiocarbamate couples have been measured in 30% v/v water in acetone and at ,μ 0.2 moll^-1 (NaNO₃) by a combination of potentiometric measurements and equilibrium constant determinations for thiolate/disulfide interchange reactions. Eº values lie in the range -250 to -340 mV which place dithiocarbamates as intermediate between thiophenolate (Eº - 540 mV) and ethylxanthate (Eº -206 mV) in reducing properties. The significant effect on EO of varying the substituents on the nitrogen in the dithiocarbamates correlates with the substituent effects on the acid dissociation constants of the parent dithiocarbamic acid and with trends in the half-wave potentials for metal-based oxidation and reduction of transition metal dithiocarbamate complexes.