STUDIES OF THE CATALYTIC ACTIVITY OF SOME PORPHYRIN AND PHTHALOCYANINE COMPLEXES FOR ACTIVATING THE OXIDATION OF SOME PHENOL DERIVATIVES BY OXYGEN

Abstract

Abstract The present work involves the following studies: 1- Autoxidation of 2,6-di-tert-butylphenol catalyzed by 5,10,15,20• tetraarylporphinatocobalt (II) complexes 67-70. Tetraphenylporphinatocobalt (II) complex 67 and tetra-(p-substituted• phenyl)porphinatocobalt (II) complexes 68-70 were prepared and their activities for catalyzing the autoxidation of 2,6-di-tert-butylphenol in dimethylformamide were investigated. AU porphyrin complexes were found to enhance the rate of autoxidation of 2,6-di-tert-butylphenol 13. The reaction products were identified as the oxidative-coupling product 3,5,3,5'-tetra-tert-butyl-4,4'-diphenoquinone (DPQ) and 2,6-di-tert• butylbenzoquinone BQ. The reaction rates and the product distributions were found to be affected by the nature of substitutents on the phenyl rings of the porphyrin ligand. Electron-donating groups favored higher conversions and higher yields of DPQ while electron-withdrawing groups gave lower reaction rates and higher yields of BQ. Gas burette measurements of dioxygen consumption were used to follow the kinetics of the autoxidation reaction.

The reaction rate constant showed linear dependence on catalyst concentration. The dependence of rate constant on both 2,6-di-tert• butylphenol concentration and pressure of dioxygen showed saturation kinetics.