Hydroxyl radical with hydrogen peroxide, reaction

Christensen, H.S., Sehested, K., and Corftizan, H., Reactions of hydroxyl radicals with hydrogen peroxide at ambient temperatures,. Phys. Chem., 86, 15-88, 1982. 

Haber-Weiss A cycle consisting of the reaction of hydroxyl radicals with hydrogen peroxide. 

Effect of pH on the Reaction of Hydroxyl Radicals with Hydrogen Peroxide in 0.05 Atmosphere N20 Solutions... 

The results of Felix et al. are based on competition between Reaction 7 and the reaction of O with 02, taking (3, 16) k(0-+o2> = 2.5 X 109M 1 sec. 1. The study of the reaction between hydroxyl radicals and hydrogen peroxide is important for the understanding of irradiated alkaline solutions, since both species are formed primarily. Besides, OH and O may form hydrogen peroxide by their recombination reactions. We used a direct method to measure the reactivity of hydroxyl radicals with hydrogen peroxide as a function of pH. In addition to Reactions 6 and 7, Reactions 8 and 9 have been considered. 

In 1949 Kolthoff and Medalia (39) showed that hydroxyl radicals from hydrogen peroxide are capable of oxidizing ethanol in accordance with the following chain reaction scheme ... 

Ozonation processes are rather complex, due to the high instability of ozone in aqueous solutions. Ozone absorbs UV photons with the maximal absorption at 253.7 nm. The decomposition of ozone under UV radiation typically occurs through three reactions direct photolysis, direct ozonation, and reactions between hydroxyl radicals and hydrogen peroxide as shown in the following reactions ... 

Figure 2.9. Glucose can enolize and reduce transition metals thereby generating superoxide free radicals (02" ), hydroxyl radicals ( OH), hydrogen peroxide (H202) and reactive dicarbonyl compounds. Adapted with permission from Wolff, S. P. (1996). Free radicals and glycation theory. In The Maillard Reaction. Consequences for the Chemical and Life Sciences, Ikan, R., ed., John Wiley Sons, Chichester, UK, 73-88.

Superoxide radical anion, hydroxyl radical, and hydrogen peroxide are known as prooxidants, whereas substances that neutralize their effects are called antioxidants. Oxidative stress occurs when the prooxidant-antioxidant balance becomes too favorable to the prooxidants. The effects of prooxidants can be neutralized by their direct reaction with small-molecule antioxidants, including glutathione, ascorbate, and tocopherols. In addition, oxidizing radicals are scavenged from a living system by several enzymes, including peroxidase, superoxide dismutase, and catalase. Oxidative lesions on DNA may be repaired by DNA repair enzymes. 

In non-aqueous solutions the Kolbe electrosynthesis takes place with high eflSciency at platinized platinum and gold, as well as at smooth platinum, anodes increase of temperature and the presence of catalysts for hydrogen peroxide decomposition, both of which have a harmful effect in aqueous solution, have relatively little influence. The mechanism of the reaction is apparently quite different in non-aqueous solutions and aqueous solutions in the former no hydroxyl ions are present, and so neither hydroxyl radicals nor hydrogen peroxide can be formed. It is probable, therefore, that direct discharge of acetate ions occurs at a potential which is almost independent of the nature of the electrode material in a given solvent. The resulting radicals probably combine in pairs, as in aqueous solution, to form acetyl peroxide, which subsequently decomposes as already described. ... 

Corrections which were made to Obtain a Precise Rate Constant for the Reaction of Hydroxyl Radicals and Hydrogen Peroxide. (1) Reactions such as 10, 11, 12, 13, and 14 compete with Reactions 6, 7, 8, and 9. 

Hydroxyl-terminated liquid polybutadienes are prepared for reactions with diisocyanates to form elastomeric polyurethanes (see Chap. 6). Such materials can be prepared by anionic polymerizations as living polymers and then quenched at the appropriate molecular weight. These polybutadienes can also be formed by free-radical mechanism. The microstructures of the two products differ, however, and this may affect the properties of the finished products. To form hydroxyl-terminated polymers by free-radical mechanism, the polymerization reactions may be initiated by hydroxyl radicals from hydrogen peroxide. 

A third example of such a reaction, and one of considerable practical importance, is the so-called tendering of fabrics by light. Fabrics dyed with certain dyes disintegrate on exposure to light, a phenomenon which caused some concern to manufacturers of curtains when it was first observed. The effect seems to be due to a photosensitized oxidation of water or hydroxide ion by electron transfer, leading to hydroxyl radicals and hydrogen peroxide which attack the fabric. 

The composition of I, and possibly its structure, may be deduced by identifying Q. Certain examples from peroxide chemistry will illustrate the scope of the method. The reactions of ferrous(nitriloacetate) and ferrous(ethylenediamine-N,N -diacetate) with hydrogen peroxide are complicated processes.1 A particular scavenger T did indeed divert the reaction at high concentrations of T. The required levels of T were, however, much higher than those that would have been needed to trap the hydroxyl radical, HO. It is thereby ruled out. With this and with spectroscopic evidence, a reactive hypervalent iron complex was suggested as the intermediate. 

Figure 4-13 shows an example from a three-dimensional model simulation of the global atmospheric sulfur balance (Feichter et al, 1996). The model had a grid resolution of about 500 km in the horizontal and on average 1 km in the vertical. The chemical scheme of the model included emissions of dimethyl sulfide (DMS) from the oceans and SO2 from industrial processes and volcanoes. Atmospheric DMS is oxidized by the hydroxyl radical to form SO2, which, in turn, is further oxidized to sulfuric acid and sulfates by reaction with either hydroxyl radical in the gas phase or with hydrogen peroxide or ozone in cloud droplets. Both SO2 and aerosol sulfate are removed from the atmosphere by dry and wet deposition processes. The reasonable agreement between the simulated and observed wet deposition of sulfate indicates that the most important processes affecting the atmospheric sulfur balance have been adequately treated in the model. 

The transformation of isoquinoline has been studied both under photochemical conditions with hydrogen peroxide, and in the dark with hydroxyl radicals (Beitz et al. 1998). The former resulted in fission of the pyridine ring with the formation of phthalic dialdehyde and phthalimide, whereas the major product from the latter reaction involved oxidation of the benzene ring with formation of the isoquinoline-5,8-quinone and a hydroxylated quinone. 

Ferrous iron, by its reaction with hydrogen peroxide in the Fenton reaction, can yield the toxic hydroxyl radical, OH, which will further potentiate oxygen toxicity. 

Dilling, W.L., Gonsior, S.J., Boggs, G.U., Mendoza, C.G. (1988) Organic photochemistry. 20. A method for estimating gas-phase rate for reactions of hydroxyl radicals with organic compounds from their relative rates of reaction with hydrogen peroxide under photolysis in 1,1,2-trichlorotrifluoroethane solution. Environ. Sci. Technol. 22, 1447-1453. 

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