Formation of Hydroxyl

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. 

Sodium bicarbonate is generally added to increase alkalinity and muriatic acid (HCl) or sodium bisulfate (NaHSO ) to reduce it. In general, with acidic sanitizers such as chlorine gas or trichloroisocyanuric acid, ideal total alkalinity should be in the 100—120 ppm range, whereas, with alkaline products such as calcium, lithium, or sodium hypochlorite, a lower ideal total alkalinity of 80—100 ppm is recommended (14). Alkalinity is deterrnined by titration with standard sulfuric acid using a mixed bromcresol green—methyl red indicator after dechlorination of the sample with thiosulfate. Dechlorination with thiosulfate causes higher readings due to formation of hydroxyl ion (32) ... 

The lithium oxide-promoted barium oxide also functions as a catalyst for the methane coupling reaction, but the mechanism is not clearly understood at the present time. The only comment that might be offered here is that the presence of ions on the surface of this material might etdrance the formation of methyl radicals drrough the formation of hydroxyl groups thus... 

Peroxytnfluoroacetic acid is used tor numerous oxidations of saturated hydrocarbons and aromatic compounds It oxidizes alkanes, alkanols, and carboxylic acids with formation of hydroxylation products [29] Oxidation of cyclohexane with peroxytnfluoroacetic acid proceeds at room temperature and leads to cyclohexyl trifluoroacetate in 75% yield, 1-octanol under similar conditions gives a mixture of isomeric octanediols in 59% yield, and palmitic acid gives a mixture of hydroxypalmitic acids in 70% yield [29]... 

Coordinated phosphate programs These programs are formulated to avoid the formation of hydroxyl alkalinity (free caustic). They tend to be employed in higher pressure WT boilers and require very careful control. Variants include congruent control and equilibrium phosphate treatment. 

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

Sun G-X, J-J Zhong (2006) Mechanism of augmentation of organotin decomposition by ferripyochelin formation of hydroxyl radical and organotin-iron ternary complex. Appl Environ Microbiol 72 7264-7269. 

Mahoney, L.R (1970). Evidence for the formation of hydroxyl radicals in the isomerisation of pemittous acid to nitric acid in aqueous solutions. J. Am. Chem. Soc. 92, 5262-5263. 

Puppo, A. and Halliwell, B. (1988). Formation of hydroxyl radicals from hydrogen peroxide in the presence of iron. Biochem. J. 249, 185-190. 

Rowley, D.A. and Halliwell, B. (1983b). Superoxide-dependent and ascorbate-dependent formation of hydroxyl radicals in the presence of copper salts a physiologically significant reaction. Arch. Biochem. Biophys. 225, 279-284. 

Gutteridge, J.M.C., Richmond, R, and HaUiweU, B. (1979). Inhibition of the iron-catalysed formation of hydroxyl radicals from superoxide and of lipid peroxidation by desferrioxamine. Biochem. J. 184, 469-472. 

The principal abiotic processes affecting americium in water is the precipitation and complex formation. In natural waters, americium solubility is limited by the formation of hydroxyl-carbonate (AmOHC03) precipitates. Solubility is unaffected by redox condition. Increased solubility at higher temperatures may be relevant in the environment of radionuclide repositories. In environmental waters, americium occurs in the +3 oxidation state oxidation-reduction reactions are not significant (Toran 1994). 

It is usually difficult to discuss unambiguously on the role of the formation of sulphate, which may explain the deactivation. Their formation can equally occur on the support and on the noble metals. The poisoning effect of S02 has been reported by Qi el al. on Pd/Ti02/Al203 [112], However, in the presence of water, the stabilisation of hydroxyl groups could inhibit the adsorption of S02 [113], Burch also suggested a possible redispersion of palladium oxide promoted by the formation of hydroxyl species [114], Such tentative interpretations could correctly explain the tendencies that we observed irrespective to the nature of the supports, which indicate an improvement in the conversion of NO into N2 at high temperature. Nevertheless, the accentuation of those tendencies particularly on prereduced perovskite-based catalysts could be in connection with structural modifications associated with the reconstruction of the rhombohedral structure of... 

H20 islands (H2Oahydroxyl group as the reaction intermediate and reveal the atomic details of hydrogen oxidation catalyzed by Pt(l 1 1). 

The reduction of Fe(III) by carotenoids may have deleterious consequences. The reduced iron Fe(II) can react with hydrogen peroxide leading to the formation of hydroxyl radical, the most reactive free radical encountered in biological systems (Equation 15.10) ... 

Shankaran, M., Yamamoto, B.K., and Gudelsky, G.A., Mazindol attenuates the 3,4-methylene-dioxymethamphetamine-induced formation of hydroxyl radicals and long-term depletion of serotonin in the striatum, J. Neurochem. 72(6), 2516-2522, 1999. 

Regarding the reductive debromination as the first step of deca-BDE degradation in mammals, Huwe and Smith [54] detected the formation of different PBDEs (three nona-BDEs, four octa-BDEs and one hepta-BDE) from deca-BDE degradation in rats, which also suggests the existence of a reductive debromination process as the first step in deca-BDE degradation in mammals. In this case, it was not identified whether the specific enzymatic system responsible for the reductive debromination and the corresponding analyses to detect the formation of hydroxylated metabolites were not carried out. 

Biological degradation of different PBDE compounds in aerobic conditions reported the formation of hydroxylated PBDEs of lower bromination than the original pollutant [26-28, 30]. There is only one report about PBDEs degradation... 

The uncatalysed p-coumaric acid oxidation led to the formation of intermediates (not shown here) almost similar to those of the catalysed reaction, without formation of dihydroxylated aromatic compounds, such as 3,4- dihydroxybenzaldehyde. This result shows that the catalyst may promote the hydroxylation of aromatic ring by enhancing the formation of hydroxyl radicals in the reaction mixture. 

The rate constant for Reaction (3) is in the range of 108 to 1091 mol-1s-1 [20]. Therefore, Reactions (3) and (4) may significantly enhance the concentration of ferrous ions and make Fenton reaction a better competitor with the peroxynitrite-inducible damage [21]. The formation of hydroxyl radicals in the reaction of superoxide with mitochondrial aconitase has... 

Formation of hydroxyl radicals has been suggested in many studies, which are considered in subsequent chapters in connection with the mechanisms of lipid peroxidation and protein and DNA destruction as well as the mechanisms of free radical pathologies. Furthermore, hydroxyl radical generation occurs under the conditions of iron overload and is considered below. 

This conclusion is partly true because superoxide is unable to abstract hydrogen atom even from the most active bisallylic positions of unsaturated compounds, while perhydroxyl radical abstracts H atom from linoleic, linolenic, and arachidonic fatty acids with the rate constants of 1-3 x 1031 mol-1 s-1 [24], However, the superoxide damaging activity does not originate from hydrogen atom abstraction reactions but from one-electron reduction processes, leading to the formation of hydroxyl radicals, peroxynitrite, etc, and in these reactions perhydroxyl cannot compete with superoxide. 

The formation of hydroxyl or hydroxyl-like radicals in the reaction of ferrous ions with hydrogen peroxide (the Fenton reaction) is usually considered as a main mechanism of free radical damage. However, Qian and Buettner [172] have recently proposed that at high [02]/ [H202] ratios the formation of reactive oxygen species such as perferryl ion at the oxidation of ferrous ions by dioxygen (Reaction 46) may compete with the Fenton reaction (2) ... 

It has been proposed [2] (Figure 24.1) that after binding to cytochrome, the substrates such as epoxides, A-oxides, nitro compounds, and lipid hydroperoxides accept two electrons and are reduced to the compounds RH(H)2. In contrast, the oxidizable substrates react with the oxygenated P-450 complex (RH)Fe2+02 (RH)Fe3+ 02 -. After transfer the second electron substrate RH is hydroxylated to ROH and cytochrome P-450 is oxidized to the starting Fe3+ state, completing the catalytic cycle. It is possible that hydroxylation proceeds through the formation of hydroxyl and carbon radicals [3], but a true role of free radicals at the final stages of hydroxylation is still obscure. 

If the mechanism of superoxide production in microsomes by NADPH-cytochrome P-450 reductase, NADH-cytochrome b5 reductase, and cytochrome P-450 is well documented, it cannot be said about microsomal hydroxyl radical production. There are numerous studies, which suggest the formation of hydroxyl radicals in various mitochondrial preparations and by isolated microsomal enzymes. It has been shown that the addition of iron complexes to microsomes stimulated the formation of hydroxyl radicals supposedly via the Fenton... 

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