Stopped-flow Kinetic Study of the Formation and Decay of the 4,4'-(Dimethylamino)diphenylmethane Radical Cation in Aqueous Solution

Article abstract of DOI:10.1039/ft9959102743

The oxidation kinetics of 4,4'-(dimethylamino)diphenylmethane (DMADPM) by Ce(IV), by the oxoanions, MnO4(1-) and Cr2O7(2-), by peroxides, namely, peroxomonosulfate, peroxodisulfate and H2O2, and by halogens viz., Cl2, Br2 and I2, to the radical cation, DMADPM^.(1+) along with further oxidation to the product monocation DMADPM(1+) have been studied by the stopped-flow technique.The first- and second-stage oxidations have been followed by monitoring the formation and decay of DMADPM^.(1+) via the absorption at 610 nm.Both formation and decay of DMADPM^.(1+) obey total second-order kinetics, first-order each with respect to or .(1+)> and .The effects of pH and temperature have also been investigated on the formation and decay of DMADPM^.(1+) and the kinetic and transition-state parameters have been evaluated and discussed with suitable reaction mechanisms.DMADPM^.(1+) was converted back into the DMADPM by the following reducing agents; ascorbic acid, dithionite, metabisulfite, sulfite and thiosulfate.The rate constants for these reactions were estimated.The experimentally determined rate constants for the oxidative electron-transfer reactions were correlated theoretically using Marcus theory and the observed and calculated rate constants show good agreement.

Full text of DOI:10.1039/ft9959102743

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