Oxidation of aromatic aldehydes and ketones by H2O2/CH3ReO3 in ionic liquids: a catalytic efficient reaction to achieve dihydric phenols

Nitrobenzene was regioselectively oxidized to 2-nitrophenol with oxygen in a reaction catalyzed by the H5PV2Mo10O40 polyoxometalate. The reaction was first order in oxygen and catalyst. 15N NMR showed the interaction between nitrobenzene and the polyoxometalate. Use of labeled 18O2, H218O, a competitive kinetic isotope experiment, and use of phenyl-tert-butylnitrone as a spin-trap and identification by EPR provided evidence for formation of a radical intermediate involving a selective intramolecular interaction at the ortho position due to formation of a H5PV2Mo10O40−nitrobenzene complex.

Selective ortho hydroxylation of nitrobenzene with molecular oxygen catalyzed by the H5PV2Mo10O40 polyoxometalate.

One-step production of phenol by selective oxidation of benzene in a biphasic system

Benzene and mesitylene (1,3,5-trimethylbenzene) are oxidized to phenol and to the corresponding aldehyde (3,5-dimethylbenzaldehyde), respectively, in CH 3 CN at room temperature, by aqueous hydrogen peroxide, in acidic medium, in reactions catalyzed by vanadium(IV or V) compounds with N , O -ligands (such as Amavadine models and related ones), namely of the types triethanolamine and (hydroxyimino)dicarboxylic acid (basic forms) or comparable ligands. The effects of the ligands, of the relative amounts of reagents and of the temperature are also reported.

Peroxidative oxidation of benzene and mesitylene by vanadium catalysts

The treatment of volatile organic compounds (VOC) emissions is a necessity of today The catalytic treatment has already proven to be environmentally and economically sound technology for the total oxidation of the VOCs However, in certain cases, it may also become economical to utilize these emissions in some profitable way Currently, the most common way to utilize the VOC emissions is their use in energy production However, interesting possibilities are arising from the usage of VOCs in hydrogen and syngas production Production of chemicals from VOC emissions is still mainly at the research stage However, few commercial examples exist This review will summarize the commercially existing VOC utilization possibilities, present the utilization applications that are in the research stage and introduce some novel ideas related to the catalytic utilization possibilities of the VOC emissions In general, there exist a vast number of possibilities for VOC utilization via different catalytic processes, which creates also a good research potential for the future

Utilization of Volatile Organic Compounds as an Alternative for Destructive Abatement

The hydroxylation of a series of aromatic hydrocarbons with hydrogen peroxide, catalyzed by iron complexes with pyrazine-3-carboxylic acid N-oxide, was investigated, operating in a biphasic reaction medium.

The new catalyst showed a high selectivity to the corresponding phenols, minimizing the over-oxidation reactions to polyoxygenated derivatives and tars which, along with dimers formation, are the major limitations of the classical Fenton’s reagent for a practical synthetic application.

In the case of alkylbenzenes, the competitive side chain oxidation at the benzylic positions also occurred. Electron rich substrates, such as anisole, were oxidized with very poor selectivity.

The reactions were carried out in a biphasic system that allows a convenient recovery and recycling of the catalyst by phase separation techniques. The catalyst showed a complete retention of activity after six consecutive reaction cycles.

The new catalyst appears as a promising tool for the direct synthesis of phenols, in alternative to the conventional multi-step methods.

Marcello Bertoli

Papers

Direct synthesis of phenols by iron-catalyzed biphasic oxidation of aromatic hydrocarbons with hydrogen peroxide