Long-lived intermediates in the reduction of chromium(VI) by D-ribose

Abstract

One of the reaction pathways in the reduction of chromium(VI) by D-ribose in aqueous perchloric acid follows the sequence Cr(VI) → I_a → I_b → Cr(III), where I_a and I_b are long-lived intermediates. A kinetic study of the reactivity of those intermediates with different substances revealed that I_a is a complex of Cr(IV) with D-ribose (or one of its partially oxidized forms), whereas I_b is a complex of Cr(II) with an organic free radical. The formation of the latter suggests that in the reduction of the intermediate Cr(IV) by the organic substrate both hydride-ion transfer and hydrogen-atom transfer are involved.