Oxidation of Thiols. IV. The Effect of Substituents on Ionization and Hexacyanoferrate (III) Oxidation of Monothiodiacylmethane

Abstract

Ionization constants, pK_a, for a set of six monothiodiacylmethanes have been determined in 50 vol% ethanol-water mixture at 25°±0.1. Excellent linear correlations are obtained when pK_a values are plotted against the substituent constant, σ_x, and the polar substituent constant, σ^*_xC6H4, for substituted phenyl groups. The regression lines are : pK_a=8.00-1.47 σ_x and pK_a=8.92-1.195 σ^*_xC6H4, respectively. The pK_a values are also correlated with the extended Hammett equation. The correlation follows the equation : pK_a=7.717-1.330σ_{I, x}-1.248σ_{R, x} The rate of the oxidation of (Ie) with hexacyanoferrate (III) was discussed at different pH values.