The kinetic activation volumes for the binding of chloride to iron(III), studied by means of a high pressure laser temperature jump apparatus

Abstract

The volumes of activation for the kinetics of the reaction of Cl − with Fe 3+ and FeOH 2+ have been determined by a laser temperature jump relaxation method at pressures up to 2.76 kbar. The results indicate that the two species, FeOH 2+ and Fe 3+ , react with Cl − by different mechanisms. The activation volume for the binding of Cl − to FeOH 2+ is positive (7.8 ± 1.0 cm 3 mol −1 ), which is consistent with a dissociative interchange mechanism. The activation volume for the binding of Cl −1 to Fe 3+ is negative (–4.5 ± 1.1 cm 3 mol −1 ), which is consistent with an associative interchange mechanism.