Hydrogen peroxide, formation

As already discussed in Sects. 6.4.5 and 6.4.6, recent developments have stimulated interest in using supported Au catalysts as active oxidation and hydrogenation agents, respectively. H2/O2 mixtures have also been used for the oxidation of propene to propene oxide using Au catalysts [169], and it is considered that a surface hydroperoxy species may be formed as the oxidant (see Sect. 6.4.5) [41,112,470]. Theoretical calculations [470] predicted that formation of H2O2 should be promoted by gold surfaces. 

Results showed that Au/ZnO and Au/Pd/ZnO catalysts exhibit some hydrogen peroxide synthesis at 308 K, although at a low rate. This is an improvement on use of the Pd catalyst that only generated water as a product (see Fig. 6.21). 

It can be concluded, therefore, that supported Au catalysts are effective for the direct synthesis of hydrogen peroxide from hydrogen and oxygen, and they may provide a significant improvement over the Pd catalysts that have been investigated previously [473,482-485]. 

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The beneficial effect of deprenyl in Parkinson s disease was su ested to be in part due to its effect on increasing the levels of SOD activity in several brain regions (Carrillo et al., 1993). Deprenyl is known to inhibit monoamine oxidase type B, which results in a reduction in hydrogen peroxide formation by blockade of the oxidative deamination of dopamine. That is believed to be the major mechanism of action of this drug in inhibiting the progression of Parkinson s disease. 

Frenkel, K. and Chrzan, K. (1987). Hydrogen peroxide formation and DNA base modification by tumor promoter-activated polymorphonuclear leukocytes. Carcinogenesis 8, 455-460. 

Oxatomide (l- 3- [4-(diphenylmethyl)-l-piperazinyl] propyl)-l,3-dihydro-2H-benzimidazol-2-one) is an antiallergy drug. Akamatsu has reported that oxatomide decreases neutrophil-generated superoxide anion and hydrogen peroxide formation in a dose-dependent manner. The authors hypothesize that the drug is inhibiting NADPH-dependent oxygen metabolism within the neutrophil (Akamatsu et al., 1993). 

Sljukic B, Bank CE, Compton RG (2004) The search for stable and efficient sonoelectroca-talysts for oxygen reduction and hydrogen peroxide formation azobenzene and derivatives. Phys Chem Chem Phys 6 4034-4041... 

Where does the hydrogen peroxide originate Many metabolic processes produce hydrogen peroxide as a byproduct. In particular, the degradation of amino acids and fatty acids leads to hydrogen peroxide formation. 

Acids catalyze the hydrolysis of hydroperoxides with hydrogen peroxide formation. 

In earlier studies [5,6] superoxide detection in mitochondria was equated to hydrogen peroxide formation. However, while it is quite possible that superoxide is a stoichiometric precursor of mitochondrial hydrogen peroxide, it is understandable that the level of hydrogen peroxide may be decreased due to the reactions with various mitochondrial oxidants. Moreover, superoxide level can be underestimated due to the reaction with mitochondrial MnSOD. Several authors [7,8] assumed that mitochondrial superoxide production may be estimated through cyanide-resistant respiration, which supposedly characterizes univalent dioxygen reduction. This method was applied for the measurement of superoxide production under in vitro normoxic and hyperoxic conditions, in spite of the finding [7] that cyanide-resistant respiration reflects also the oxidation of various substrates (lipids, amino acids, and nucleotides). Earlier,... 

Highley T. Effect of carbohydrate and nitrogen on hydrogen peroxide formation by wood decay fungi in solid medium. FEMS Microbiol Lett 1987 48 373-378. 

Abele-Oeschger D, Tug H, Rottgers R (1997) Dynamics of UV-driven hydrogen peroxide formation on an intertidal sandflat. Limnol Oceanogr42 1406-1415... 

If an aqueous solution saturated with oxygen is sonicated hydrogen peroxide formation occurs. This is due to hydroxyl ( OH) and hydroperoxyl ( OOH) radical recombination outside the cavitation bubble (Scheme 4.1). These radicals result from HjO and O2 homolytic cleavage inside the bubble and have been observed by spin trapping experiments (Scheme 4.1) [19]. 

Plant leaves, hydrogen peroxide formation, 636 Plant tissue... 

But, in addition, it was shown that the water vapor concentration was without the effect on hydrogen peroxide formation which should be expected from this mechanism. The suggestion was made that the reaction might perhaps be better represented by the mechanism suggested by Taylor and Marshall ... 

We have conducted experiments to improve the selectivity of the reaction for hydrogen peroxide formation, with a special attention to the influence of the reactor will. These experimental results are interpreted by a simplified kinetic model, which is fairly well explained by knowledge of the rate of the free radical reaction. 

V (at oxygen consumption over 90%) indicates that Reactor III gave the highest selectivity (ca. 60% ) as to hydrogen peroxide formation, and the lowest yield of by-products from pyrolysis and combustion. Reactor... 

V gave poorer results than III or IV. The result with Reactor IV fell between those of Reactor III and V. Reactor II gave almost the same yield of hydrogen peroxide as Reactor III with somewhat lower selectivity for propylene formation. Therefore, the effect of reactor pretreatment on selectivity for hydrogen peroxide formation is ... 

The quartz reactor is more suitable for the hydrogen peroxide formation than the stainless steel reactor, the yield of hydrogen peroxide in... 

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