OXIDATION OF THREOSE-SERIES PENTOSES AND HEXOSES BY SODIUM N-CHLORO-P-TOLUENESULFONAMIDE

The kinetics and mechanism of oxidation of threose-series hexoses and pentoses by chloramine-T in alkaline medium was investigated. Kinetic studies with D-galactose, D-sorbose, D-xylose, and D-lyxose showed tha t the rate of the reaction was first order with respect to sugar and c hloramine-T, and second order with respect to hydroxide ion. p-Toluene sulfonamide and chloride ions, the reduced products of chloramine-Tr, have no effect on the reaction rate. The rate increases with increase in ionic strength of the medium, and the dielectric effect is negative . Proton inventory studies in H2O-D2O mixtures suggested a single tran sition state. Product analysis for D-gulose, D-idose, L-sorbose, D-gal actose, D-talose, D-tagatose, D-xylose, and D-lyxose revealed that all lyxose-series hexoses gave mainly mixtures of lyxonic and threonic ac ids with minor proportions of hexonic, xylonic and glyceric acids, whe reas all xylose-series hexoses gave mixtures of lyxonic, threonic and glyceric acids with minor amounts of xylonic and hexonic acids. Xylose and lyxose gave mixtures consisting mainly of lyxonic, threonic, and glyceric acids with minor proportions of xylonic acid. From the result s of kinetic studies, reaction stoichiometry, and product analysis, a possible mechanism for the oxidation of threose-series sugars with chl oramine-T is suggested. (C) 1998 Elsevier Science Ltd. All rights rese rved.