Kinetics and Mechanism of Electron Transfer to Heptavalent Manganese byDL-Aspartic Acid in Alkaline Aqueous and Micellar Media

Abstract

The kinetics and mechanism of the electron transfer ofdl-Aspartic acid (Asp) by Mn (VII) in alkaline medium has been studied spectrophotometrically over the range2.0≤103[Asp]≤5.0 mol dm−3;0.01≤[OH-]≤0.05 mol dm−3;298≤T≤318 K andI=0.05 mol dm−3(KNO3). The reaction exhibits first-order dependence in[MnO4-]Tbut shows fractional-order dependence in both[Asp]Tand[OH−]T. The reaction was studied in the presence of sodium dodecyl sulfate (SDS); an increase in the rate with the increase in the micellar concentration was observed. The products were characterized by spectral analysis. A mechanism involving free radicals is proposed. Asp bindsMnO4-to form a complex that subsequently decomposes to products. Activation parametersΔH° (kJ mol−1) andΔS° (JK−1 mol−1) for the reaction are5.62±0.35and−227.65±1.1, respectively. The negative value ofΔS° indicates that oxidation occurs via inner sphere mechanism.