Kinetic Studies on the Complexation of Chromium(III) with some Amino Acids in Aqueous Acidic Medium

Abstract

The kinetics of the formation of the 1:3 complex of chromium(III) with L-glutamic acid and DL-lysine were studied spectrophotometrically at γmax= 550 and 550 nm. The reaction was found to be first order in both reactants. Increasing the hydrogen ion concentration from 3.2 × 10-5to 1.0 × 10-3mol · dm-1retarded the reaction rate which is of the form kobs= a + b[H4]-1. Values of 28.8 and 63.6 kJ · mol-1were obtained for the energy of activation and -184 and -116J-K-I· mol-1for the entropy of activation for L-glutamic acid and DL-lysine. The logarithms of the formation constants of the two complexes were found to be 5.9 and 5.1.