Kinetics of reaction of iron(III) with some aliphatic acids in aqueous solution at 20°C

Abstract

The temperature-jump relaxation technique has been used to study the kinetics of the reaction of iron(III) with acetic, propionic, and chloroacetic acids in aqueous solution at 20°C and I= 1.0 M over the acidity range 0.010 M ⩽[H⁺]⩽0.95 M. The kinetic data show that the formation of the iron(III) acetate and propionate complexes occur via an acid-independent path, and, simultaneously, via a second path dependent on the hydrogen ion concentration. A third path, inversely proportional to the hydrogen ion concentration, also contributes to the formation of the ferric chloroacetate complex. The estimated rate constants are similar to those previously found for analogous reactions of complex formation of iron(III). This provides additional support to the hypothesis that the rate-determining step is the loss of a water molecule coordinated to the iron(III).