An Efficient Aerobic Oxidation For P-xylene To P-toluic Acid By Unsymmetrical Schiff Base Manganese(III) Complexes With Pendant Benzo-10-Aza-Crown Ether Or Morpholino-Groups
Unsymmetrical Schiff base Mn(III) complexes with pendant aza-crown or morpholino groups have been synthesised and studied as catalysts in aerobic oxidation of p-xylene to p-toluic acid (PTA). The oxidation of p-xylene to p-toluic acid with air at 120 °C under normal atmospheric pressure occurred efficiently in the presence of aza-crown ether substituted unsymmetrical Schiff base Mn(III) complexes. Significant selectivity (up to ~90%) and conversion levels (up to ~40%) were obtained. The effect of the pendant aza-crown ether group in Mn(III) Schiff base complexes on the oxidation of p-xylene was also investigated by comparison with the pendant morpholino-group analogues. The addition of Na+ cation accelerated the rate of conversion of p-xylene to p-toluic acid.