Kinetic studies on the complexation of aqua chromium (III) with DL-leucine in aqueous acidic media

Kinetics of formation of 1:2 complex between chromium (III) and DL-leucine was studied spectrophotometrically at λmax =540 nm. The reaction was found to be first order in both reactants. Increasing hydrogen ion concentration from 2.5×10- à 10-3 mol.dm-3 decreased the reaction rate: kobs =a + b[H+]-1. Activation parameters were evaluated to be 38 kJ.mol-1 and -159 JK-1.mol-1, for the enthalpy and entropy of activation respectively. A value of log K = 2.9 at 42 ○C was obtained for the formation constant of the complexe ()