Kinetic studies on the complexation of chromium(III) with some amino acids in aqueous acidic medium

The kinetics of the formation of the 1:3 complex of chromium(III) with L-glutamic acid and DL-lysine were studied spectrophotometrically at lambda(max) = 550 and 550 nm. The reaction was found to be first order in both reactants. Increasing the hydrogen ion concentration from 3.2 x 10(-5) to 1.0 x 10(-3) mol dm 3 retarded the reaction rate which is of the form k(obs) = a + b[H-dagger](-1). Values of 28.8 and 63.6kJ . mol(-1) were obtained for the energy of activation and -184 and -116J . K-1 . mol(-1) fur 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.