Kinetic and mechanistic investigations and thermodynamic quantities for different steps involved in the mechanism of oxidation of procainamide by hexacyanoferrate(III) in aqueous alkaline medium: a spectrophotometric study

Abstract

The kinetics of oxidation of procainamide by alkaline hexacyanoferrate(III) at a constant ionic strength of 1.10 mol dm−3 has been studied spectrophotometrically at 25 °C. The stoichiometric analysis indicates that one mole of procainamide requires two moles of hexacyanoferrate(III). The reaction products are identified and confirmed by IR, NMR, and GC–MS spectral studies. The reaction is first order with respect to oxidant, Fe(CN) 6 3− and less than unit order with respect to procainamide and alkali concentrations. Increasing ionic strength and decreasing dielectric constant of the medium increases the rate of reaction. The added products did not have any significant effect on the rate of reaction. Based on the experimental results, a suitable mechanism is proposed and the following rate law is derived and verified. Activation parameters are evaluated with respect to the slow step of the mechanism and thermodynamic quantities are also calculated. Voltammetric behavior of procainamide is also made.