ON THE ELECTROCHEMICAL REACTIVITY OF ANOMERS - ELECTROCATALYTIC OXIDATION OF ALPHA-D-GLUCOSE AND BETA-D-GLUCOSE ON PLATINUM-ELECTRODES IN ACID AND BASIC-MEDIA

Polarimetric studies of D-glucose solutions were carried out at low te mperature (2 degrees C). This procedure allowed us to stabilize the so lutions of D-glucose and to differentiate the behaviour of the two mai n dissolved anomeric forms (alpha or beta). In particular, the depende nce of their stability on the pH of the electrolytic solutions was fol lowed and their electrochemical reactivity was tested. Using cyclic vo ltammetry it was possible to demonstrate that, of the two possible pyr anic forms of D-glucose, only beta-D-glucose exhibited an appreciable reactivity at platinum electrodes, i.e. alpha-D-glucose was almost unr eactive at low temperature. This difference in reactivity between anom ers has never been shown clearly in any of the previous electrochemica l studies of glucose. Long-term electrolysis was also performed. Ionic chromatography as well as in situ IR spectroscopic experiments allowe d us to conclude that the oxidation of D-glucose in basic media at low temperature leads selectively to formation of the delta-gluconolacton e, which later undergoes hydrolysis forming D-gluconate as a final pro duct. Mechanisms are proposed and discussed.