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 degrees 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 [HClO4] was found to lie between 1 and 2. The rate was found to be independent of ionic strength as well as of any inhibition effect of Mn(II). The formation of superoxochromium(III) ion was detected in an aerated solution of chromium(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.