Kinetics and mechanism of the oxidation of some substituted aldonitrones by quinolinium chlorochromate in aqueous DMF medium in the absence and presence of oxalic acid

The kinetics of the oxidation of aldonitrones (nitrone) by quinolinium chlorochromate (QCC) was determined in 50 % DMF-water in the absence and presence of oxalic acid in order to study the effect of oxalic acid. It was considered worthwhile to investigate whether it undergoes co-oxidation or just functions as a catalyst in the reaction. The reaction was followed iodometri- cally. Under the employed experimental conditions, the reaction is first order each with respect to concentration of nitrone, QCC, and oxalic acid and frac- tional order with respect to H + concentration. There was no discernible effect with increasing in ionic strength but the rate of oxidation decreased with de- creasing dielectric constant of the medium. Addition of MnSO4 had a signi- ficant and acrylonitrile no effect on the reaction rate. A mechanism involving protonated nitrone and QCC as the reactive oxidant is proposed. The activation parameters were calculated and are presented.