Hydroxyl radical water

Oxygen Superoxide Hydrogen peroxide Hydroxyl radical Water... 

Sedlak DL, Andren AW. The effect of sorption on the oxidation of polychlorinated-biphenyls (PCBs) by hydroxyl radical. Water Res 1994 28 1207-1215. 

WesterhofF P, Aiken G, Amy G, DeBroux J. Relationship between the structure of natural organic matter and its reactivity towards molecular ozone and hydroxyl radical. Water Res 1999 33 2265-2276. 

The reduction potential for the hydroxyl/water couple was not precisely known until recently [106,107]. Based on older values for the hydroxyl radical/water couple one will find higher values of 0.8 V [108] or 0.46 V [34] in earlier papers by the present author. The implication of the value of 0.32 V for the reduction... 

The diffusion kinetic analysis of spur-decay processes requires a model of the initial distribution of reactive species produced by radiolysis. These reactants are able to diffuse from their original location and, if they encounter another reactant, reaction can occur. Most work on spur-decay processes has been with water as the solvent and with such solute species as N2O, HCOO as electron scavenging solutes, OH as a proton scavenger, and alcohols to scavenge hydroxyl radicals. Water is so polar that coulomb interactions may be disregarded and the reactants treated as uncharged radical species. Most of the reactions thought to be important were listed in Sect. 4.2. Many of these reactions occur at or close to the diffusion-limited rate and most of the rate coefficients have been measured. It should be recalled that a spur is a localised cluster of... 

Sonoelectrochemistry has been employed in a number of fields such as in electroplating for the achievement of deposits and films of higher density and superior quality, in the deposition of conducting polymers, in the generation of highly active metal particles and in electroanalysis. Furtlienuore, the sonolysis of water to produce hydroxyl radicals can be exploited to initiate radical reactions in aqueous solutions coupled to electrode reactions. 

Products other than hydroperoxides are formed in oxidations by reactions such as those of equations 11 and 12. Hydroxyl radicals (from eq. 4) are very energetic hydrogen abstractors the product is water (eq. 11). 

A third source of initiator for emulsion polymerisation is hydroxyl radicals created by y-radiation of water. A review of radiation-induced emulsion polymerisation detailed efforts to use y-radiation to produce styrene, acrylonitrile, methyl methacrylate, and other similar polymers (60). The economics of y-radiation processes are claimed to compare favorably with conventional techniques although worldwide iadustrial appHcation of y-radiation processes has yet to occur. Use of y-radiation has been made for laboratory study because radical generation can be turned on and off quickly and at various rates (61). 

In the presence of water vapor, oxygen atoms formed by uv radiation react to form hydroxyl radicals (35), which can destroy ozone catalyticaHy. 

The stability of the alkali metal ozonides increases from Li to Cs alkaline-earth ozonides exhibit a similar stability pattern. Reaction of metal ozonides with water proceeds through the intermediate formation of hydroxyl radicals. 

Effect of Hydroxyl Radicals on Ozone Depletion. Hydroxyl radicals, formed by reaction of ( D) oxygen atoms with water or CH, can destroy ozone catalyticahy (11,32) as shown in the following reactions. 

A chlorohydrin has been defined (1) as a compound containing both chloio and hydroxyl radicals, and chlorohydrins have been described as compounds having the chloro and the hydroxyl groups on adjacent carbon atoms (2). Common usage of the term appHes to aUphatic compounds and does not include aromatic compounds. Chlorohydrins are most easily prepared by the reaction of an alkene with chlorine and water, though other methods of preparation ate possible. The principal use of chlorohydrins has been as intermediates in the production of various oxitane compounds through dehydrochlorination. 

The attack on the aromatic nucleus by hydroxyl radicals is probably analogous to that by phenyl and methyl radicals, Eq. (34a,b). Evidence that the first step is the addition of hydroxyl radical to benzene, rather than abstraction of a hydrogen atom, has recently been adduced from a study of the radiolysis of water-benzene mixtures. The familiar addition complex may undergo two reactions to form the phenolic and dimeric products respectively, Eq. (34a,b). Alternative mechanisms for the formation of the dimer have been formulated, but in view of the lack of experimental evidence for any of the mechanisms further discussion of this problem is not justified. 

Irradiation of dilute aqueous solutions results in the interaction ofthe ionizing radiation with water molecules. The radiolysis of water produces hydrated electrons (eaq ", G = 2.8), hydrogen atoms (G = 0.6) and hydroxyl radicals (G = 2.8) which react with the molecules of the solutes. The use of special scavengers can convert one species to another, e.g. 

At elevated temperatures, methylene carbons cleave from aromatic rings to form radicals (Fig. 7.44). Further fragmentation decomposes xylenol to cresols and methane (Fig. 7.44a). Alternatively, auto-oxidation occurs (Fig. 1.44b ). Aldehydes and ketones are intermediates before decarboxylation or decarbonylation takes place to generate cresols and carbon dioxide. These oxidative reactions are possible even in inert atmospheres due to the presence of hydroxyl radicals and water.5... 

Most of the trichloroethylene used in the United States is released into the atmosphere by evaporation primarily from degreasing operations. Once in the atmosphere, the dominant trichloroethylene degradation process is reaction with hydroxyl radicals the estimated half-life for this process is approximately 7 days. This relatively short half-life indicates that trichloroethylene is not a persistent atmospheric compound. Most trichloroethylene deposited in surface waters or on soil surfaces volatilizes into the atmosphere, although its high mobility in soil may result in substantial percolation to subsurface regions before volatilization can occur. In these subsurface environments, trichloroethylene is only slowly degraded and may be relatively persistent. 

In broad terms, the following types of reactions are mediated by the homolytic fission products of water (formally, hydrogen, and hydroxyl radicals), and by molecular oxygen including its excited states—hydrolysis, elimination, oxidation, reduction, and cyclization. 

Brezonik PL, J Fulkerson-Brekken (1998) Nitrate-induced photoysis in natural waters controls on concentrations of hydroxyl radical photo-intermediates by natural scavenging agents. Environ Sci Technol 32 3004-3010. 

Vaughan PP, NV Blough (1998) Photochemical formation of hydroxyl radicals by constituents of natural waters. Environ Sci Technol 32 2947-2953. 

Gas-phase reactions have been carried out in 160 mL quartz vessels, and the products analyzed online by mass spectrometry (Brubaker and Hites 1998). Hydroxyl radicals were produced by photolysis of ozone in the presence of water ... 

Ascorbate is known to act as a water-soluble antioxidant, reacting rapidly with superoxide, hydroxyl and peroxyl radicals. However, reduced ascorbate can react non-enzymatically with molecular oxygen to produce dehydroascorbate and hydrogen peroxide. Also, ascorbate in the presence of light, hydrogen peroxide and riboflavin, or transition metals (e.g. Fe, Cu " ), can give rise to hydroxyl radicals (Delaye and Tardieu, 1983 Ueno et al., 1987). These phenomena may also be important in oxidative damage to the lens and subsequent cataract formation. 

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