Kinetics and mechanism of oxidation monosaccharides by sodium-N-bromobenzenesulphonamide in alkaline medium

Abstract

Kinetic studies of the oxidation of <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-fructose, <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-glucose, <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-galactose, <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-mannose, <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-xylose, <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-ribose, <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-lyxose and <img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-arabinose by bromamine-B (sodium-N-bromobenzene sulphonamide, BAB) have been carried out in alkaline medium at 30°. The reaction shows a zero order dependence on [BAB] and fraction orders in [sugar]₀ and [HO^-]₀. The rates tend to level off at higher [sugar]₀ and [HO^-]₀.Variation in ionic strength of the medium, and the addition of benzene sulphonamide, Cl^- and Br^- ions do not alter the rate while lowering the dielectric constant of the medium increases the rate slightly. Solvent isotope and proton-inventory studies have been made. Enolization rate coefficients and activation parameters for rate limiting step have been determined from Michaelis-Menten type of plots. A probable scheme for oxidation of monosaccharides through a common intermediate, 1,2-enediol has been proposed.