Kinetics of oxidation of β-isophorone to keto-isophorone catalyzed by manganese Schiff base complex using molecular oxygen

Abstract

Kinetic investigations were carried out on the oxidation of β-isophorone (β-IP) to keto-isophorone (KIP) catalyzed by [LMn(III)(Cl)], (where, L=bis-salicylaldehydeethylenedi-imine, salen) at temperature in the range 10–27°C and partial pressure 0.2–3 atm of molecular oxygen. β-IP gave mainly KIP as the oxidation product under the reaction conditions studied. Initial rate approach was adopted to evaluate kinetic parameters of the reaction. From the kinetic investigations, it was found that the rate of oxidation of β-IP showed a first-order dependence with respect to catalyst and substrate concentrations, and half-order dependence on the partial pressure of oxygen. The effect of temperature on the rates of oxidation was also investigated and from the Arrhenius plot of −ln rate vs. 1/ T, the activation energy estimated is 16.12 kcal mol −1. Thermodynamic activation parameters such as enthalpy, entropy and free energy of the reaction were calculated from the known thermodynamic equations. Based on the kinetic investigations, a plausible mechanism for manganese salen complex catalyzed oxidation of β-IP to KIP has been proposed.