Investigation of the kinetics of formation of 1 : 1 complex between chromium(III) with 1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate ion in aqueous acidic media

Abstract

The kinetics of formation of the 1: 1 complex of chromium(III) with 1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate (1,3-pddadp) were followed spectrophotometrically at λmax= 557 nm The reaction was first-order in chromium(III) Increasing the 1,3-pddadp concentration from 2.2 × 10-2to 0.11 mol dm-3accelerated the reaction rate Increasing the hydrogen ion concentration from 1.995 × 10-5to 6.31 × 10-4mol dm-3retarded the reaction rate The reaction rate was also retarded by increasing ionic strength and dielectric constant of the reaction medium A mechanism was suggested to account for the results obtained which involves ion-pair formation between the various reactants Values of 22 kJ mol-1and -115 J K-1mol-1were obtained for the energy and the entropy of activation, respectively, which indicate an associative mechanism The logarithm of the formation constant of the 1: 1 complex formed was 11.3 © 2013 Taylor & Francis.