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Iron tetrasulfophthalocyanine (FePcTs) catalyzes oxidation of 3,4-dimethoxybenzyl alcohol (DMBA) to ≤ 11% 3,4-dimethoxybenzaldehyde (DMBAL), ≤ 7% 2-hydroxymethyl-5-methoxy-1,4-benzoquinone (HMBQ) and other unidentified products in aqueous hydrogen peroxide at 30–40°C. The FePcTs is unstable under the reaction conditions, as UV-visible spectra show its complete decomposition in 2 min. Immobilization of the FePcTs on an anion exchange resin gave oxidation and catalyst decomposition results similar to those in homogeneous solutions. In contrast, potassium monopersulfate gave 75% conversion of DMBA to 11–13% DMBAL and at least 8 other products at 30°C using either free or immobilized FePcTs, and 71% conversion in absence of FePcTs. Potassium monopersulfate also oxidized 2,4,6-trichlorophenol to 100% conversion in 6 min at 30°C in the presence of FePcTs and 75% conversion in the absence of FePcTs. Potassium monopersulfate bleaches FePcTs within seconds at 30°C. Thus FePcTs is not a useful catalyst for DMBA oxidation because of its oxidative instability, and potassium monopersulfate is a powerful oxidant even without a catalyst. |
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