Influence of microwave irradiation in the cyclohexane oxidation catalyzed by Fe(III) complexes

In this work we have studied the effect of microwave irradiation in cyclohexane oxidation catalyzed by the Fe(III) complexes: [Fe(BMPA)Cl3] 1, [Fe(MPBMPA)Cl3] 2, [Fe(PBMPA)Cl2] 3 and [Fe(PABMPA)Cl2](ClO4) 4, in acetonitrile as solvent and with H2O2 or t-BuOOH as oxidant. The system was studied in presence and absence of solvent, in open and closed vessel and in homogeneous and heterogeneous catalytic conditions. In the later case the complexes were impregnated in alumina. The complexes were able to oxidize cyclohexane under microwave irradiation in cyclohexanol, cyclohexanone, cyclohexyl hydroperoxide, tert-butyl cyclohexyl peroxide and adipic acid, with yields from 1.4% to 17.0%. The best results were obtained in closed vessel, where the temperature reached in the reaction medium was greater than in the reactions in open vessel. The use of the complexes impregnated in alumina led to lower yields compared to the free complexes. The reaction volume also influenced the yield, with an optimum volume of 15 mL. Reactions under conventional heating were carried out for the sake of comparison, yielding better results than reactions under MW irradiation.