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

Abstract

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.

Progress in the biosynthesis of bio-based PET and PEF polyester monomers

“…The addition of Na + significantly accelerates the conversion of p -xylene to p -methylbenzoic acid. 16 Subsequently, the group synthesized four asymmetric salicylaldehyde amine bis-Schiff bases as catalysts with 90% selectivity and 70% conversion in the aerobic oxidation of p -xylene to p -methylbenzoic acid. 17…”

“…The addition of Na + significantly accelerates the conversion of p-xylene to p-methylbenzoic acid. 16 Subsequently, the group synthesized four asymmetric salicylaldehyde amine bis-Schiff bases as catalysts with 90% selectivity and 70% conversion in the aerobic oxidation of p-xylene to p-methylbenzoic acid. 17 Similarly, the oxidation of terephthalic benzene to TPA was achieved using catalysts containing cobalt acetate, manganese acetate, CoBr 2 and MnBr 2 , and the maximum yield of TPA (93.5%) was determined to be obtained at a reaction temperature of 100 °C and a Br/Co atomic ratio of 3.…”