Kinetics and Mechanism of the Oxidation of Formate and Malonate with (trans-1,2-Cyclohexanediamine-N,N,N',N'-tetraacetato)manganate(III) in Aqueous Medium

Article abstract of DOI:10.1246/bcsj.65.517

The kinetics of the reduction of (trans-1,2-cyclohexanediamine-N,N,N',N'-tetraacetato)manganate(III) by formate and malonate have been investigated in the pH regions 3.6-5.25 and 4.5-8.30 respectively at constant ionic strength and temperature.In the oxidation of formate slight initial increase in absorbance was observed, whereas for malonate oxidation no such indication was noted.Both the reactions are overall second-order with first-order on both the oxidant and reductants.A general rate law for the oxidation of formate and malonate can be given as -d/dt = k * , where k is the electron-transfer rate constant.The reactivity of HCOO^- is (3.26 +/- 0.16) * 10^-5 dm³ mol^-1 s^-1 (kK') and that of Hmal^- and mal^2- are (4.28 +/- 0.12) * 10^-5 (k₁) and (6.05 +/- 0.12) * 10^-4 (k₂) dm³ mol^-1 s^-1 respectively at 40 deg C.A plausible inner-sphere mechanism has been suggested for the formate oxidation, whereas malonate oxidation has been interpreted by an outer-sphere mechanism.