Kinetics of complexation of transition metal ions with some organic acids in various media

Abstract

Kinetic study of formation of 1:2 complex between chromium (III) and nicotinic acid in weak acid aqueous solution was investigated spectrophotometrically at λ=575 nm. Experimental results showed that the reaction took place in multiple steps. Increasing hydrogen ion concentration led to a decreasing in the reaction rate. The rate constants k1obs and k2obs increased with decreasing the dielectric constant of the reaction medium indicating that the reaction is an ion pair type. The kinetics of oxidation of chromium nicotinate complex by NaIO4 to Cr(VI) have been studied spectrophotometrically. The reactions exhibited biphasic kinetic behavior through which an intra molecular electron transfer process took place. The kinetics of substitution of aquo-ligand from hydroxopenta-aquo Ferric (III) by N-Phthaloylglycine in aqueous medium has been studied spectrophotometrically. The rate law involving the formation of ion-pair has been established in the pH 2.8 and 50ºC.