Kinetics and mechanism of electron-transfer in the aquaethylene-diaminetetraacetatochromium(iii)/n-bromosuccinimide reaction

Summary The oxidation of aquaethylenediaminetetraacetatochromium(III) [Cr(HEDTA)(H₂O)] with N-bromosuccinimide (NBS) to yield chromium(VI) has been studied spectrophotometrically over the 20–40° C range. The rate is first order with respect to both reactants and increases with decreasing [H⁺] between pH 6.0 and 6.8. The thermodynamic activation parameters were calculated. The experimental rate law is consistent with a mechanism in which the deprotonated [Cr(EDTA)(OH)]^2- and protonated [Cr(EDTA)(H₂O)]^- are the reactive species. It is proposed that electron transfer proceeds via an inner sphere mechanism.Abstracted from the PhD thesis of Alaa El-Din M. Abdel-Hady.