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

✍ Scribed by Zaheer Khan; Kabir-Ud-Din

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 136 KB
• Volume: 31
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/(sici)1097-4601(1999)31:6<409::aid-kin2>3.0.co;2-8

✦ Synopsis

The kinetics of oxidation of N,N-dimethylformamide by chromium(VI) has been studied spectrophotometrically in aqueous perchloric acid media at 20ЊC. The rate showed a first-order dependence on both [Cr(VI)] and [DMF], and increased markedly with increasing [H ϩ ]. The order with respect to [HClO 4 ] 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 HClO 4 . The proposed mechanism, involving two reaction pathways, leads to the rate law,

[DMF] (k I K a2

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), CO 2 and dimethylamine.