Dissociation kinetics of the solvated electron species in methylamine and methylamine–ammonia mixtures

Abstract

Potential-sweep voltammetric and potential-step chronoamperometric experiments were made at −50 °C with solvated electrons in methylamine containing LiCl, KI, or CsI. The dissociation rate constants of the ion pairs, (M+•es−), M being alkali metal and es− free solvated electron, were greater than 103 s−1. The pseudo-first-order rate constant of the dissociation of K− into the one-electron species, es− and (K+•es−) in rapid equilibrium, was determined as 40 s−1 by chronoamperometry with 0.5 M KI solutions. The formation constants of K− from the one-electron species determined by chronoamperometry and voltammetry were 4.5 × 104 M−1 and 5.6 × 104 M−1, respectively. An addition of a small amount of ammonia to methylamine caused a decrease in the formation constant of K− and an increase in its dissociation rate constant. The appendix deals with a theoretical treatment of chronoamperograms for an electrode process preceded by the dissociation of a dimer. The boundary value problem was solved by the explicit finite difference method and the analytical method which was based on the concept of reaction layer.