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 Fe3+ and FeOH2+ have been determined by a laser temperature jump relaxation method at pressures up to 2.76 kbar. The results indicate that the two species, FeOH2+ and Fe3+, react with Cl− by different mechanisms. The activation volume for the binding of Cl− to FeOH2+ is positive (7.8 ± 1.0 cm3 mol−1), which is consistent with a dissociative interchange mechanism. The activation volume for the binding of Cl−1 to Fe3+ is negative (–4.5 ± 1.1 cm3 mol−1), which is consistent with an associative interchange mechanism.