Kinetic study of the dissociation of Ba 2+-C222 cryptate in binary demethylsulfoxide-acetonitrile mixtures

Abstract

The dissociation rates of the Ba 2+-C222 cryptate in different dimethylsulfoxide-acetonitrile mixtures have been studied spectrophotometrically using murexide as a suitable metallochromic indicator. The activation parameters E a, ΔH ‡ and ΔS ‡ for the dissociation of the cryptate were determined from the temperature dependence of the dissociation rate constants (ka). The correlation of the dissociation rate constant with the stability constant (K s) of the barium cryptate was investigated. There is a linear relationship between log K s and the activation parameters E a, ΔH ‡ and ΔS ‡ and the mole fraction of acetonitrile in the mixed solvent.