Kinetics and mechanism of the reaction between dimethylformamide and chromium(VI)

The kinetics of oxidation of N,N-dimethylformamide by chromium(VI) has been studied spectrophotometrical ly in aqueous perchloric acid media at 20 deg rees C. The rate showed a first-order dependence on both [Cr(VI)] and [DMF] , and increased markedly with increasing [H+]. The order with respect to [H ClO4] was found to lie between 1 and 2. The rate was found to be independen t of ionic strength as well as of any inhibition effect of Mn(II). The form ation of superoxochromium(III) ion was detected in an aerated solution of c hromium(VI), DMF and HClO4. The proposed mechanism, involving two reaction pathways, leads to the rate law, rate = K-a1 [HCrO4-] [DMF] (k(I) K-a2 [H+] (2) + k(II)[H+]). The first pathway, with rate constant k(I), involves the formation of chromium(V) and a free radical. The second pathway, with rate constant k(II), involves the formation of Cr(IV), CO2 and dimethylamine. (C ) 1999 John Wiley & Sons, Inc.