Kinetics and mechanism of oxidation of chromium(III)-L-glutamic acid complex by periodate

Abstract

410-414The kinetics of oxidation of the chromium(III)-L-glutamic acid complex, [CrIII(L)2(H2O)2]+ , by periodate in aqueous solutions has been found to obey the following-equation: d[CrVI]/dt=k2K5[CrIII]T[IVII] T /{1+([H+]/K1)+K5[IVII] T} where k2 is the rate constant for the electron transfer process, K1the equilibrium constant for dissociation of [CrIII(L)2 (H2O)2+] to of [CrIII(L)2 (H2O)(OH)] + H+, and K5 the pre-equilibrium formation constant. Values of k2 = 2.93×10-3 s-1,K1 = 6.26 ×10-4 mol dm-3 and K5 = 88.41 dm3 mol-1 have been obtained at 30°C and I= 0.2 mol dm-3 . Thermodynamic activation parameters have been calculated. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of IO4- to chromium(III)