Kinetics of oxidation of some monosaccharides by pyridinium chlorochromate (PCC)

Abstract

The oxidation kinetics of glucose, considered as a model compound for reducing sugars, with pyridinium chlorochromate in perchloric acid medium has revealed a linear correlation between the observed rate constant <i>k</i>_obs and [glucose],[H⁺]. A comparison of <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-glucose oxidation with its various C-l and C-2 substituted derivatives shows that inductive, steric and shielding effects may all be important which explains the reactivity as 2-deoxy-<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>-glucose > 1=<i>o</i>-methyl-α-<img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-glucopyranoside > 2-amino-2- deoxy-<img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-glucose hydrochloride. A comparison between <i>α</i> and <i>β</i> anomers of some monosaccharides reveals that b anomer is oxidised faster than a-anomers. Further, activation energy and thermodynamic parameters have been evaluated for <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-glucose oxidation and mechanism consistent with experimental observation is attempted.