Conditional oxidation

Benzene with no alkyl side chain and no benzyhc hydrogens undergoes a different reaction under these conditions Oxidation of the ring occurs to convert benzene to its epoxide... 

Halophenols without 2,6-disubstitution do not polymerize under oxidative displacement conditions. Oxidative side reactions at the ortho position may consume the initiator or intermpt the propagation step of the chain process. To prepare poly(phenylene oxide)s from unsubstituted 4-halophenols, it is necessary to employ the more drastic conditions of the Ullmaim ether synthesis. A cuprous chloride—pyridine complex in 1,4-dimethoxybenzene at 200°C converts the sodium salt of 4-bromophenol to poly(phenylene oxide) (1) ... 

Oxidative stability is highly important because it deals with the degradation of polymers under actual performance conditions. Oxidative stability, as applied to urethanes, refers to the combination of oxygen and heat or oxygen and light that causes degradation of urethanes. 

When cast iron is exposed to high temperatures under oxidising conditions, oxidation of the metal results, with the formation of a surface scale. In addition, the dimensions of the component become distorted. Although such dimensional changes can occur also in inert atmospheres or in vacuum, the evidence available suggests that this growth is frequently associated with oxidation, and accordingly it is appropriate to consider it as an aspect of the corrosion of the iron. 

In acid conditions oxide films are not usually present on the metal surface and the cathodic reaction is primarily that of hydrogen discharge rather than oxygen reduction. Thus, inhibitors are required that will adsorb or bond directly onto the bare metal surfaces and/or raise the overpotential for hydrogen ion discharge. Inhibitors are usually organic compounds... 

A practical method of modification of polysaccharides by clean oxidation using H2O2 as oxidant and cheap iron phthalocyanine as catalyst has been developed. Since no acids, bases or buffers and no chlorinated compounds were used, a pure product can be recovered without additional treatment. Importantly, this flexible method provides materials with a wide range of DScho and DScooh just by an appropriate choice of the reaction conditions. Oxidized polysaccharides thus obtained possess various, tailormade hydrophihc/hydrophobic properties which have been tested successfully in cosmetic and other apphcations. 

Precipitation may result from incompatible brine. Hydrolysis may detoxify wastes. Complexation may increase or decrease mobility depending on condition. Oxidation or reduction of wastes may occur. 

Care must be used in selecting the adsorbent. Some are also good catalysts, and under the right conditions oxidation or tires could occur. Also, when there are unsaturated compounds, polymerization could occur. When that happens regeneration is usually impossible.27... 

Chand et al. [88] degraded phenol under sonication at different frequencies with H2O2 and O3 in presence of zero valent iron and copper. The effectiveness of 300 kHz sonochemical reactor was found to be the maximum for the generation of OH radicals among 20, 300 and 520 kHz. The complete removal of phenol was achieved when sonicated with 300 kHz frequency with zero valent iron compared to zero valent copper. In their mechanism it was supposed that at first iron metal was corroded in the presence of hydrogen peroxide, under acidic conditions, oxidizing Fe° to Fe2+, which on further reaction with H202 produce OH radicals and Fe3+. The Fe° then reduces the Fe3+ back to Fe2+ and the chain was maintained as... 

The oxidation of some anhydroaldopento-benzimidazoles13 was found to entail uptake of more than the calculated amount of oxidant per mole. This apparent anomaly was further explored by Huebner, Ames and Bubl,14 and their work culminated in the discovery that periodate, under the usual conditions, oxidizes certain methylene carbon atoms, namely, those activated by two flanking carbonyl groups. This type of oxidation (a-hydrogen oxidation) was simultaneously observed (by Fleury and Courtois16) to occur on the periodate oxidation of malonic acid. A satisfactory reaction was obtained under the following conditions. 

Under suitable conditions, oxidation of /V-alkyl-a-amino acids, accompanied by decarboxylation, has made it possible to carry out regioselective syntheses of nitrones which were utilized in the synthesis of 1-azabicyclic alkaloids (Scheme 2.6) (48, 49). 

Autoxidation of secondary acetonitriles under phase-transfer catalytic conditions [2] avoids the use of hazardous and/or expensive materials required for the classical conversion of the nitriles into ketones. In the course of C-alkylation of secondary acetonitriles (see Chapter 6), it had been noted that oxidative cleavage of the nitrile group frequently occurred (Scheme 10.7) [3]. In both cases, oxidation of the anionic intermediate presumably proceeds via the peroxy derivative with the extrusion of the cyanate ion [2], Advantage of the direct oxidation reaction has been made in the synthesis of aryl ketones [3], particularly of benzoylheteroarenes. The cyanomethylheteroarenes, obtained by a photochemically induced reaction of halo-heteroarenes with phenylacetonitrile, are oxidized by air under the basic conditions. Oxidative coupling of bromoacetonitriles under basic catalytic conditions has been also observed (see Chapter 6). 

Halogens are frequently used as oxidation agents and, under two-phase conditions, they can either be employed as ammonium complex halide salts [3], or in the molecular state with or without an added quaternary ammonium catalyst [4]. Stoichiometric amounts of tetra-n-butylammonium tribromide under pH controlled conditions oxidize primary alcohols and low-molecular-weight alkyl ethers to esters, a,cyclic ethers produce lactones [3], and secondary alcohols yield ketones. Benzoins are oxidized to the corresponding benzils (80-90%) by the tribromide salts in acetonitrile in the presence of benzoyl peroxide [5]. 

In the usual experiment for the electrochemical oxidation of methanol, this reactant is added to a supporting electrolyte. When an electrochemical measurement is executed under this condition, oxidation of both bulk methanol and adsorbed species are mixed up and analyses are difSciiit... 

Although CY-diketones are only rarely isolated from aqueous permanganate oxidations there is conclusive proof that they are intermediates in the reaction (16). Of-Diketones are resistant to further oxidation under anhydrous conditions and can thus be isolated in good yields from the phase transfer assisted reactions. Howeverf under aqueous conditions oxidative cleavage takes place rapidly, thus preventing the accumulation of these products. 

Oxidation of phenols and aromatic amines using HRP is generally of little synthetic value, as oligomers and polymers are the main products (5, 260). Under certain conditions oxidative coupling of phenols or naphthols to give biaryls can be achieved, but with low selectivity (262). In contrast, HRP can catalyze a number of useful oxidative N-and 0-deaIkyIation reactions that are relatively difficult to carry out synthetically. This area has been described in detail by Meunier (263). A method for the preparation of optically active hydroperoxides using HRP C has been developed (264). Optically pure (S)-hydroperoxides... 

Alkaline soil conditions exist in most semi-arid to arid conditions. Oxidizing sulfides should produce a change in pH in the surface soil as confirmed by Hamilton et al. (2004), and especially in the soil microlayer where an upward moving front of H" accumulates, as shown nearly 40 years ago. If this soil micro-layer is sampled... 

Antimony is stable in dry air and not readily attacked by moisture slowly oxidized by moist air. Under controlled conditions oxidation may result forming tri-, tetra-, and pentaoxides 86203, 86264 and 86265, respectively. 

Hajipour and coworkers prepared benzyltriphenylphosphonium peroxymonosulfate (BnPhsPHSOs) in a very high yield (95%) and purity (99%). This new oxidizing reagent was applied successfully in various deprotection reactions such as the conversion of oximes, phenylhydrazones, 2,4-dinitrophenylhydrazones and semicarbazones to the corresponding carbonyl compounds in the presence of bismuth chloride under nonaqueous conditions . Oxidative deprotection of trimethylsilyl ethers, tetrahydropyranyl ethers and ethylene acetals with BnPh3PHS05 under microwave irradiation affords the corresponding carbonyl compounds in very high yields (equation 71). The same reaction also proceeds under nonaqueous conditions ". 

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