Equilibria in thiol–disulphide interchanges. Part V. Reaction of some aminoethanethiols with 4,4′-dithiobis(benzenesulphonic acid)

Abstract

Thiol–disulphide interchange reactions generally involve two consecutive competitive equilibria. Equations have been developed that relate the composition of the equilibrium mixture to the equilibrium constants, both for simple interchange and for the case in which the thiol formed in the reaction is ionised. Various relationships are made evident. Determination of only one thiol in the equilibrium mixture does not permit calculation of the constants for the two equilibria, but these constants can be obtained from the concentration of a single thiol species in two equilibrium mixtures derived from different initial concentrations. The equations are applied to the determination of approximate equilibrium constants for the interchange of 2-aminoethanethiol, and of eight derivatives, with 4,4′-dithiobis(benzenesulphonate). There appears to be no obvious correlation between these constants and the radioprotective ability of the substances.