Oxidation of some monosaccharides by hexavalent manganese in aqueous alkaline medium: A kinetic and mechanistic study

✍ Scribed by K. Venkateswara Rao; M. Thirupathi Rao; M. Adinarayana

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 335 KB
• Volume: 27
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550270605

✦ Synopsis

Abstract

The kinetics of oxidation of some monosaccharides viz., D‐ribose, D‐xylose, and D‐arabinose, D‐glucose, D‐fructose, D‐galactose, 2‐deoxyglucose, and α‐methyl glucopyranoside by MnO~4~^2−^ in aqueous alkaline medium have been studied. The rate of oxidation has been found to be first‐order both with respect to [oxidant] and [sugar]. The rate is independent of [OH^−^] under experimental conditions of [OH^−^] > 0.5 M where the oxidant is stable. The effect of ionic strength is negligible on the rate. A mechanism involving the formation of a 5‐membered cyclic intermediate complex between MnO~4~^2−^ and 1,2‐enediol form of the sugar is proposed. The intermediate complex decomposes to give products in the subsequent slow step. The involvement of 1,2‐enediol form receives support from the reaction of α‐methyl glucopyranoside, which exists in ring structure in alkaline solution reacting much slower than glucose with MnO~4~^2−^ under similar conditions. Second‐order rate constant k″ and activation parameters have been evaluated. The series of reactions exhibits a clear demonstration of applicability of isokinetic phenomenon where Arrhenius plots for all the reactions are found to intersect at a common point (295 K). © 1995 John Wiley & Sons, Inc.