Kinetics of Acidic Mn(VII) Oxidation of Acetaldehyde in Aqueous and 5% Ethanol-Water Solvents

Abstract

Kinetics of acidic Mn(VII) oxidation of acetaldehyde in aqueous and 5% ethanol-water solvents were studied via pseudo-first order condition at λmax 525nm. The reaction showed a first order dependence with respect to acetaldehyde concentration, [Mn(VII)], fractional order to [H+] and independent on the ionic strength of the solution. Michaelis-Menten plot showed the existence of an intermediate complex and dependence on hydrogen ion is in the form kobs= a + b[H+]. However, oxidation reaction is generally faster in non-aqueous solvent than in aqueous solvent. Product analysis revealed the presence of carboxylic acid and stoichiometric study suggests the consumption of 2 moles of MnO4-by 3 moles of acetaldehyde in both solvents. Thermodynamic parameters of activation were obtained from Arrhenius and Erying's equations. A plausible associative mechanism in agreement with kinetic and spectroscopic results was proposed.