Abstract
The kinetics of the reduction of chromium(VI) to chromium(III) by L-sorbose in HClO4 was studied between 30 and 80degreesC at various concentrations of reactants and acidities in both aqueous and micellar sodium dodecyl sulfate (SDS)/TritonX-100(TX-100) solutions. Under pseudo-first-order conditions the reaction rate is fractional-order in [L-sorbose] and [H+], and first-order in [Cr-VI] both in the absence and in the presence of surfactant micelles. The reaction is accelerated by addition of manganese(II) and is routed through the same mechanism as shown by the kinetic studies in the absence and presence of surfactants. The rate enhancement in presence of SDS/TX-100 micelles indicates that essentially all the reactive species are bound to micelles under the experimental conditions. The observed catalyses are explained with the modified Menger and Portnoy model. Inorganic salts (NaBr, LiBr, NH4Br) inhibit the reaction in presence of SDS micelles, which confirms exclusion of the reactive species of chromium(VI) from the reaction site. (C) 2003 Wiley Periodicals, Inc.