Oxidation of 2,6-Di-tert-butylphenol by dioxygen catalyzed by tetrasodium phthalocyaninatocobalt(II) tetrasulfonate in aqueous micellar media

Abstract

The oxidation of 2,6-di-tert-butylphenol by dioxygen has been investigated in aqueous micellar aggregates of cetyltrimethylammonium bromide (CTAB) using tetrasodium phthalocyaninatocobalt(II) tetrasulfonate (CoPcTsNa 4 ) as catalyst. The CTAB/CoPcTsNa 4 system showed enhanced catalytic activity in the oxidation of 2,6-di-tert-butylphenol compared to that observed in the oxidation reaction in the absence of CTAB. 2,6-Di-tert-butyl-1,4-benzoquinone and 3,5,3',5'-tetra-tert-butyl-4,4-diphenoquinone were identified as reaction products. The initial rate constants of auto-oxidation reaction was found to increase with increasing the pH range from 7.0 to 13.0. The rate constants k obs of auto-oxidation reaction showed linear dependence on catalyst concentration. The rate of auto-oxidation reaction was found to fit a Michealis-Menten kinetic model for the saturation of catalyst sites with increasing 2,6-di-tert-butylphenol concentration and dioxygen pressure. Tetrasodium phthalocyaninatocobalt(II) tetrasulfonate in aqueous micellar solution of CTAB was found to be mainly monomeric.

Oxidative C–C coupling of 2,6-di-tert-butylphenol in aqueous media via catalytically active molybdate surfactants

“…The oxidation of DTBP to DPQ is a relatively wellknown reaction, 11 and it is precisely for this reason that it is an excellent candidate for the following proof-of-concept studies. On the other hand, published examples of this transformation occurring in water are few 12,13 and do not involve catalytic surfactants, but rather transition metal catalysts dissolved within the micelle. 12 Slight modifications to published procedures were used to obtain the long chain N-alkyliminodiacetic acids (H 2 C n IDA, where n = 10, 12, 14).…”

“…On the other hand, published examples of this transformation occurring in water are few 12,13 and do not involve catalytic surfactants, but rather transition metal catalysts dissolved within the micelle. 12 Slight modifications to published procedures were used to obtain the long chain N-alkyliminodiacetic acids (H 2 C n IDA, where n = 10, 12, 14). 14 Upon reaction with 1 equiv.…”

“…As the oxidant concentration was increased, the amount of DPQ decreased, suggesting perhaps the formation of the over-oxidized benzoquinone (BQ) derivative. [11][12][13] When the identical larger-scale reaction was performed with 10 equiv. H 2 O 2 , the residue isolated by extraction displayed a product distribution of 85% DPQ and 7% BQ by NMR, with an additional 8% DTBP remaining unreacted.…”