Kinetics and Mechanism of Interaction between Chromium(III) and Ethylenediaminetetra-3-Propinate in Aqueous Acidic Media

Abstract

The kinetics of the formation of 1:1 complex of chromium(III) with ethylenediaminetetra-3-propinate (EDTP) was fol-lowed spectrophotometrically at  max = 557 nm. The reaction was found to be first order in chromium(III) and was ac-celerated by EDTP. Increasing the pH from 3.3 to 4.7 accelerated the reaction rate, the reaction rate was 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 species of the reactants. Values of the activation parameters obtained indicate an associative mechanism.