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

Kinetic investigations were carried out on the oxidation of beta-isophorone (beta-IP) to keto-isophorone (KIP) catalyzed by [LMn(III)(Cl)], (where, L = bis-salicylaldehydeethylenedi-imine, salen) at temperature in the range 1 0-27 degrees C and partial pressure 0.2-3 atm of molecular oxygen. beta-IP gave mainly KIP as the oxidation product under the reaction conditions stud ied. Initial rate approach was adopted to evaluate kinetic parameters of th e reaction. From the kinetic investigations, it was found that the rate of oxidation of beta-IP showed a first-order dependence with respect to cataly st and substrate concentrations, and half-order dependence on the partial p ressure 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 acti vation energy estimated is 16.12 kcal mol(-1). Thermodynamic activation par ameters such as enthalpy, entropy and free energy of the reaction were calc ulated from the known thermodynamic equations. Based on the kinetic investi gations, a plausible mechanism for manganese salen complex catalyzed oxidat ion of beta-IP to KIP has been proposed. (C) 2000 Elsevier Science B.V. All rights reserved.