Kinetics and mechanism of oxidation of aquaethylenediaminetetraacetatocobaltate(II) by N-bromosuccinimide in aqueous acidic solution

The oxidation of aquaethylenediaminetetra-acetatocobaltate(II) [Co(EDTA)(H2O)](-2) by N-bromosuccinimide (NBS) in aqueous solution has been studied spectrophotometrically over the pH 6.10-7.02 range at 25 degrees C. The reaction is first-order with respect to complex and the oxidant, and it obeys the following rate law: Rate = kEK(2)K(3) [Co-II(EDTA)(H2O)(-2)](T)[NBS]/([H+]+K-2) It is proposed that the electron transfer proceeds via an inner-sphere mechanism due to the formation of the initial cobalt(III), which is converted slowly to the final product.