A kinetic study of oxidation of β-cyclodextrin by permanganate in aqueous media

Kinetic data for the permanganate-p-cyclodextrin redox system are reported for the first time. Conventional spectroscopic method was used to monitor the progress of the reaction. The reaction is first order in both [MnO4-] and [beta-cyclodextrin]. The [H+] markedly increase the oxidation rate. Formation of an intermediate (Mn(IV)) observed during the course of reaction at 420 nm. Mn(III) is also formed in a rapid step by reaction of beta-cyclodextrin and Mn(IV). Increase in [F-] causes the rate to decrease. One of the primary -OH group of alpha-D-glucopyranose unit of beta-cyclodextrin is responsible for the oxidation. An autocatalytic effect has been observed due to Mn(II) ions formed as a product of the reaction. The rate of oxidation of D-glucose is higher in comparison to beta-cyclodextrin for the same concentration. Reduction of mercuric chloride indicates free radical mechanism operates during the course of reaction. The energy, enthalpy and entropy of activation have been calculated and mechanism agreement with the observation is suggested. (c) 2007 Elsevier B.V. All rights reserved.