Stopped flow ESR study of the action of carbohydrates on ascorbic acid oxidation in aqueous solution.

The influence of added carbohydrate on the decay kinetics of the ascorbic acid free radical generated in deaerated aqueous solutions by the action of potassium ferricyanide on ascorbic acid has been studied. Addition of carbohydrate (less than or equal to 0.5M) generally leads to a small decrease in radical decay rate. In our system this probably arises from reduced reactant diffusion in solutions of increased viscosity rather than the preferential chelation previously suggested to explain inhibition in the copper (II) catalyzed oxidation. The ascorbic acid free radical shows negligible tendency to react with glucose, sorbitol or maltose. The decrease in its decay rate observed on addition of carbohydrate is probably caused by the increase in solvent viscosity.