Abstract
The kinetics of cerium(TV) oxidation of D-fructose in aqueous H 2 so 4 medium has been studied spectrophotometrically. The reaction is first order in [Ce(IV)] in the presence of excess [D-fructose]. The effect of H,SO 4 on the UV-vis. spectrum of cerium(IV) is discussed. The overall process shows first order dependence on [D-fructose] whereas that in [H2SO4] is complex. The oxidation kinetics of D-fructose with cerium(IV) has indicated a rate-limiting bimolecular reaction between cerium(IV) and D-fructose leading to the formation of a free radical and Ce(III). Increase in [H2SO4] accelerates the reaction rate. The active oxidant (cerium(IV)sulphato) and reductant species are H4Ce(SO4)(4) and beta-D-fructopyranose, respectively. The proposed mechanism corresponds to the rate law
d[Ce(IV)(T)/dt = k(1)K(c)K(4)K(3)K(2)K(1)[H+](4) [D-fructose] [Ce(SO4)(4)(4-)] / 1 + K-1 [H+] (1 + K-2 [H+]) + K1K2K3 [H+](3)(1 + K-4 [H+])
The reactivity of cerium(IV) has also been compared with chromium(VI) and vanadium(V).