Thallous–thallic exchange in solutions of the chloroacetic acids

Abstract

The two-electron exchange between thallous and thallic ions has been studied to determine the effect of complex formation of thallic ion with the chloroacetate ions. This work confirms and extends earlier results by Brubaker and Andrade, and shows that the rate, R, of the exchange can be described by the equation (1) where the rate R//_{[Tl^I][Tl^III]}=k₀+k₁K₁[HA]//_{1 +K1[HA]}(1), constants k₁ are 0·22 × 10^–4, 0·68 × 10^–4, 2·50 × 10^–4, and 6·25 × 10^–4 l. mole^–1 sec.^–1, respectively, for acetic acid and mono-, di-, and tri-chloroacetic acids. The value of k₀ is 4·50 × 10^–4 l. mole^–1 sec.^–1. Thus, the first three ligands retard the exchange, while the fourth accelerates the reaction. Spectrophotometric confirmation of the existence and of the composition of the acetato- and the several chloroacetato-complexes of Tl^III was obtained by the method of continuous variation. Values are derived for the equilibrium constants, K₁, for the formation of the 1 : 1 complexes.