Catalysis hydrogen peroxide

Under acid catalysis, hydrogen peroxide adds 1,4 to mesityl oxide (1) to form the hydroperoxide (2) this cyclizes to the peroxide (3), which combines with hydrogen peroxide to give as the final product crystalline mesityl oxide peroxide (4, m.p. 122°). ... 

Keywords Oxidation, green chemistry, heterogeneous, catalysis, hydrogen peroxide... 

Keywords Alkyl C-H oxidation Aminopyridine ligands Bioinspired catalysis Hydrogen peroxide Iron coordination complexes Nonheme oxygenases Selectivity... 

Hydrogen peroxide may react directiy or after it has first ionized or dissociated into free radicals. Often, the reaction mechanism is extremely complex and may involve catalysis or be dependent on the environment. Enhancement of the relatively mild oxidizing action of hydrogen peroxide is accompHshed in the presence of certain metal catalysts (4). The redox system Fe(II)—Fe(III) is the most widely used catalyst, which, in combination with hydrogen peroxide, is known as Fenton s reagent (5). 

The mechanism and rate of hydrogen peroxide decomposition depend on many factors, including temperature, pH, presence or absence of a catalyst (7—10), such as metal ions, oxides, and hydroxides etc. Some common metal ions that actively support homogeneous catalysis of the decomposition include ferrous, ferric, cuprous, cupric, chromate, dichromate, molybdate, tungstate, and vanadate. For combinations, such as iron and... 

Oxidation. Hydrogen peroxide is a strong oxidant. Most of its uses and those of its derivatives depend on this property. Hydrogen peroxide oxidizes a wide variety of organic and inorganic compounds, ranging from iodide ions to the various color bodies of unknown stmcture in ceUulosic fibers. The rate of these reactions may be quite slow or so fast that the reaction occurs on a reactive shock wave. The mechanisms of these reactions are varied and dependent on the reductive substrate, the reaction environment, and catalysis. Specific reactions are discussed in a number of general and other references (4,5,32—35). 

Because the peroxodisulfate salts are all made electrochemicaHy, the electrical energy cost is a significant part of thek manufacturing cost. The 1994 world capacity for peroxodisulfate salts was about 75,000 metric tons, valued at about 30 x 10 . The principal appHcations are in polymerization catalysis and the market broadly tracks the plastics business. The Caro s acid business is difficult to quantify because the product itself is not commercial but made on-site from purchased hydrogen peroxide. 

Enzyme catalysis. An enzyme in the potato is catalyzing the decomposition of a hydrogen peroxide solution, as shown by the bubbles of oxygen. 

An example of a reaction that is subject to homogeneous catalysis is the decomposition of hydrogen peroxide in aqueous solution ... 

Micellar catalysis to enhance or diminish the rate of chemical reactions is well known [97]. Of somewhat greater interest is the influence of micelles on competing reactions, e.g., proton-catalyzed reactions. An example related to the effect of alkanesulfonates is the epoxidation of simple aliphatic olefins. The reaction of olefins and hydrogen peroxide catalyzed by strongly acidic Mo(VI)... 

As mentioned in Sect. 2.2, phosphine oxides are air-stable compounds, making their use in the field of asymmetric catalysis convenient. Moreover, they present electronic properties very different from the corresponding free phosphines and thus may be employed in different types of enantioselective reactions, m-Chloroperbenzoic acid (m-CPBA) has been showed to be a powerful reagent for the stereospecific oxidation of enantiomerically pure P-chirogenic phos-phine-boranes [98], affording R,R)-97 from Ad-BisP 6 (Scheme 18) [99]. The synthesis of R,R)-98 and (S,S)-99, which possess a f-Bu substituent, differs from the precedent in that deboranation precedes oxidation with hydrogen peroxide to yield the corresponding enantiomerically pure diphosphine oxides (Scheme 18) [99]. 

This concerted reduction by two ferrous species eliminates H02- (or O2 ) as an intermediate and explains the weak catalysis by Cu(II) (which is strong for V([II) and V(IV) autoxidations). Weiss has suggested that the species Fe. 02.Fe may be a stable intermediate, but Wells explains the presence of two Fe(Il) species in the rate law in terms of a pre-existing dimeric form of Fe(lf) containing an H2O bridge, for which there is evidence . The reduction is completed via the Fenton reaction vide infra). The hydrogen peroxide dianion is probably never free but is protonated whilst complexed to Fe(III). 

New materials are also finding application in the area of catalysis reiated to the Chemicals industry. For example, microporous [10] materials which have titanium incorporated into the framework structure (e.g. so-calied TS-1) show selective oxidation behaviour with aqueous hydrogen peroxide as oxidizing agent (Figure 5). Two processes based on these new catalytic materials have now been developed and commercialized by ENl. These include the selective oxidation of phenol to catechol and hydroquinone and the ammoxidation of cyclohexanone to e-caproiactam. 

Heteropoly acids can be synergistically combined with phase-transfer catalysis in the so-called Ishii-Venturello chemistry for oxidation reactions such as oxidation of alcohols, allyl alcohols, alkenes, alkynes, P-unsaturated acids, vic-diols, phenol, and amines with hydrogen peroxide (Mizuno et al., 1994). Recent examples include the epoxidations of alkyl undecylenates (Yadav and Satoskar, 1997) and. styrene (Yadav and Pujari, 2000). 

It gives rise to an extremely violent reaction with hydrogen peroxide. This is certainly due to the catalysis of the decomposition of peroxide caused by the phosphoric acid produced by water. 

In contact with fluorine, when it is cold, nickel oxide glows. It reacts violently with hydrogen peroxide (catalysis of its decomposition ). Finally, in contact with a mixture of hydrogen sulphide and air, it glows and causes this gaseous mixture to detonate. 

Indeed, when present in concentrations sufficient to overwhelm normal antioxidant defences, ROS may be the principal mediators of lung injury (Said and Foda, 1989). These species, arising from the sequential one-electron reductions of oxygen, include the superoxide anion radical, hydrogen peroxide, hypochlorous ions and the hydroxyl radical. The latter species is thought to be formed either from superoxide in the ptesence of iron ions (Haber-Weiss reaction Junod, 1986) or from hydrogen peroxide, also catalysed by ferric ions (Fenton catalysis Kennedy et al., 1989). 

Liu HY, Abdalmuhdi I, Chang CK, Anson FC. 1985. Catalysis of the electroreduction of dioxygen and hydrogen peroxide by an anthracene-linked dimeric cobalt porphyrin. J Phys Chem 89 665. 

In the M. capsulatus (Bath) system, all three components are necessary to obtain turnover with NADH as the reductant (57). With the M. trichosporium OB3b system, protein B is apparently not required (27). Instead, in this latter system, protein B increases the initial rates of the catalytic hydroxylation reaction (27). Catalysis can be achieved by means of a shunt pathway with hydrogen peroxide and Hox alone from both organisms (58-60). The efficiency of the shunt pathway, however, varies significantly. With M. trichosporium OB3b, alcohol yields greater than those obtained with the completely reconstituted system have been observed (58). Furthermore, upon addition of protein... 

One of the exciting results to come out of heterogeneous catalysis research since the early 1980s is the discovery and development of catalysts that employ hydrogen peroxide to selectively oxidize organic compounds at low temperatures in the liquid phase. These catalysts are based on titanium, and the important discovery was a way to isolate titanium in framework locations of the inner cavities of zeolites (molecular sieves). Thus, mild oxidations may be run in water or water-soluble solvents. Practicing organic chemists now have a way to catalytically oxidize benzene to phenols alkanes to alcohols and ketones primary alcohols to aldehydes, acids, esters, and acetals secondary alcohols to ketones primary amines to oximes secondary amines to hydroxyl-amines and tertiary amines to amine oxides. 

Metal-ion catalysis of hydrogen peroxide decomposition can generate perhydroxyl and hydroxyl free radicals as in Scheme 10.26 [235]. The catalytic effects of Fe2+ and Fe3+ ions are found to be similar [235]. It is not necessary for the active catalyst to be dissolved [237], as rust particles can be a prime cause of local damage. The degradative free-radical reaction competes with the bleaching reaction, as illustrated in Scheme 10.27 [237]. Two adverse consequences arise from the presence of free radicals ... 

Liao, C.J., Chung, T.L., Chen, W.L. and Kuo, S.L. (2007) Treatment of pentachlorophenol-contaminated soil using nano-scale zero-valent iron with hydrogen peroxide. Journal of Molecular Catalysis A Chemical, 265, 189—194. 

The violent decomposition observed on adding charcoal to cone, hydrogen peroxide is mainly owing to catalysis by metallic impurities present and the active surface of the charcoal, rather than to direct oxidation of the carbon [1], Charcoal mixed with a trace of manganese dioxide ignites immediately on contact with cone, peroxide [2],... 

The electrochemical rate constants for hydrogen peroxide reduction have been found to be dependent on the amount of Prussian blue deposited, confirming that H202 penetrates the films, and the inner layers of the polycrystal take part in the catalysis. For 4-6 nmol cm 2 of Prussian blue the electrochemical rate constant exceeds 0.01cm s-1 [12], which corresponds to the bi-molecular rate constant of kcat = 3 X 103 L mol 1s 1 [114], The rate constant of hydrogen peroxide reduction by ferrocyanide catalyzed by enzyme peroxidase was 2 X 104 L mol 1 s 1 [116]. Thus, the activity of the natural enzyme peroxidase is of a similar order of magnitude as the catalytic activity of our Prussian blue-based electrocatalyst. Due to the high catalytic activity and selectivity, which are comparable with biocatalysis, we were able to denote the specially deposited Prussian blue as an artificial peroxidase [114, 117]. 

V. Mechanism of Catalysis by Tetraamide Macrocyclic Fem-TAML Activators of Hydrogen Peroxide, Functional Catalase-Peroxidase... 

In another procedure [522] the sample of seawater (0.5-3 litres) is filtered through a membrane-filter (pore size 0.7 xm) which is then wet-ashed. The nickel is separated from the resulting solution by extraction as the dimethylglyoxime complex and is then determined by its catalysis of the reaction of Tiron and diphenylcarbazone with hydrogen peroxide, with spectrophotometric measurement at 413 nm. Cobalt is first separated as the 2-nitroso-1-naphthol complex, and is determined by its catalysis of the oxidation of alizarin by hydrogen peroxide at pH 12.4. Sensitivities are 0.8 xg/l (nickel) and 0.04 xg/l (cobalt). 

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