Oxidation by peroxides

The slow step is thought to be loss of one ligand from the complex. These chelates and those with a series of ring-substituted Schiff bases undergo acid fission at exactly the same rate as oxidation by peroxide. 

Aminoanthracene forms a Schiff base with dimethylacetaldehyde (isobutyral-dehyde). This compound can be oxidized by peroxide under basic conditions to form 9-formamidoanthracene and acetone in dimethylformamide as a solvent [54, 55], CL from this system can be observed in other aprotic solvents as well. A limited amount of work has been done with the CLs of Schiff bases or anthracene derivatives. Presumably, this will change in the future. 

Nitriles are susceptible to hydrolysis via nucleophilic attack of water on the electropositive carbon atom, especially under strongly acidic and basic conditions (Fig. 29). Nitriles hydrolyze to imidic acids, which tautomerize to amides. Amides can be hydrolyzed further to carboxylic acids, although much more slowly. Nitriles are susceptible to oxidation by peroxides under mildly basic conditions (e.g., pH 7.5-8) as has been documented in the case... 

Thiols are susceptible to oxidation by peroxides, molecular oxygen, and other oxidizing processes (e.g., radical-catalyzed oxidation) (Fig. 67). Because thiols easily complex with transition metals, it is believed that most thiol autoxidation reactions are metal-catalyzed (108). Autoxidation of thiols is enhanced by deprotonation of the thiol to the thiolate anion. Thiol oxidation commonly leads to disulfides, although further autoxidation to the sulfinic and, ultimately, sulfonic acid can be accomplished under basic conditions. Disulfides can be reduced back to the thiol (e.g., upon addition of a reducing agent such as dithiothreitol). Thiols are nucleophilic and will readily react with available electrophilic sites. For a more thorough discussion, see Hovorka and Schoneich (108) and Luo et al. (200). 

Bortolini, O., Conte, V., Di Furia, F. and Modena, G. (1986) Metal catalysis in oxidation by peroxides. Part 25. Molybdenum- and tungsten-catalyzed oxidations of alcohols by diluted hydrogen peroxide under phase-transfer conditions. /. Org. Chem., 51, 2661. Barak, G. and Sasson, Y. (1989) Effect of phase-transfer catalysis on the selectivity of hydrogen peroxide oxidation of aniline. /. Org. Chem., 54, 3484. 

DNA binding during aminofluorene catalyzed oxidation by peroxide... 

TABLE II. DNA OR POLYRIBONUCLEOTIDE ADDUCT FORMATION WITH AMINOFLUORENE FOLLOWING OXIDATION BY PEROXIDES... 

Another consequence of these findings is that the same adduct can be formed by a free radical mediated pathway from MAB following a one electron oxidation by peroxides as that formed from methylol or me thimine by a two electron oxidation catalyzed by cytochrome P450. Clearly identification of the GSH adducts of carcinogens in vivo may not distinguish both metabolic activation systems. It is also still not clear whether cytochrome P450 and peroxidases form common intermediates during N-demethylation reactions (22-24). 

Ferrihydrite catalysis of hydroxyl radical formation from peroxide has also shown experimental results consistent with a surface reaction [57]. The yield of hydroxyl radical formation was lower for ferrihydrite than for dissolved iron, resulting in a higher peroxide demand to degrade a given amount of pollutant. As mentioned above, although ferrihydrite exhibited a faster rate of peroxide decomposition than goethite or hematite, the rate of 2-chlorophenol degradation with these catalysts was fastest for hematite [55], In other studies, quinoline oxidation by peroxide was not observed when ferrihydrite was used as catalyst [53]. 

A15.1.2.3 Nitriles. Nitriles are classihed as carboxylic acid derivatives because they are converted to carboxylic acids on hydrolysis. Like the hydrolysis of amides, nitrile hydrolysis is irreversible in the presence of acids or bases. Acid hydrolysis yields an ammonium ion and a carboxylic acid, e.g., cimeti-dine [15]. Nitriles are also susceptible to oxidation by peroxides under mildly basic conditions (e.g., pH 7.5 to 8). 

Thiols are susceptible to oxidation by peroxides, molecular oxygen, and other oxidizing processes (e.g., radical-catalyzed oxidation). Thiol oxidation commonly leads to disulfides (R—S—S—R), although further autoxidation to the sulfinic (R—SO2H) and sulfonic acid (RSO3H) may occur under basic conditions. 

Cziczo DJ, Thomson DS, Murphy DM (2001) Ablation, flux, and atmospheric implications of meteors inferred from stratospheric aerosol. Science 291 1772-1775 Dachs J, Eisemeich SJ (2000) Adsorption onto aerosol soot carbon dominates gas-particle partitioning of polycyclic aromatic hydrocarbons. Environ Sci Technol 34 3690-3697 Dalleska NF, Colussi AJ, Hyldahl AM, Hoffmaim MR (2000) Rates and mechanism of carbonyl sulfide oxidation by peroxides in concentrated sulfuric acid. J Phys Chem A 104 10794-10796 D Almeida GA, Schitz L (1983) Number, mass, and volume distributions of mineral aerosol and soils of the Sahara. J Clim Appl Meteorol 22 233-243... 

Yamazaki, 1971), dictates the correct experimental conditions for POase assays POase is divalently oxidized by peroxide to Compound I, which is, in turn, reduced to the initial state by 2 successive univalent interactions with H-donors. Compound II is the one-electron oxidized, intermediate form. Some H-donors, e.g. o-dianisidine, produce a direct, two-electron transfer reduction (Claiborne and Fridovich, 1979a). Nitrogenous compounds (nucleophilic catalysts pyridine, imidazole), may stimulate this transfer (Claiborne and Fridovich, 1979b). 

These results testify that the /0-diketonates of europium are not always passive and may significantly contribute to the production of CL as a result of their oxidation by peroxides. This circumstance should be taken into account when lanthanide complexes are used as inert activators for studying of chemi- or bioluminescent reactions. 

Because of this difference between the two bases Kuhn and Wasser-mann concluded that the reduction of ferric to ferrous cannot be the ratecontrolling step in the formation of the complex. They suggested that after ferrous ion has been formed in this way, it can either be oxidized by peroxide or react with the base to give the complex. If the rate of the latter reaction is faster with dipyridyl than with phenanthroline this will lead to the observed difference between them. Simon and Haufe (67) do not agree with this and hold the view that the production of ferrous ion by the reaction... 

This is rapidly established from the left-hand side, and therefore the position is independent of the time of illumination. The reverse reaction occurs slowly in the dark and in the absence of hydrogen peroxide. Aquo-pentacyanoferrite formed in this way decomposes peroxide catalytically by a reaction which is not specified. At the same time it is oxidized by peroxide to aquopentacyanoferrate... 

Terminal alcohols. The alkylzirconium (IV) complexes (CsHs)2Zr(R)Cl are oxidized by peroxides or peracids to alcohols in about 40-70% yield. The only by-products are alkanes arising from protonolysis of the C—Zr bond. Actually, in many cases oxygen (dry) is the best reagent (60-80% yield). 

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