Hypochlorous anion

Chlorate is the most important halate and is produced, on an industrial scale, by electrolysis of a halide solution in a diaphragmless cell, which promotes efficient mixing. This arrangement allows the chlorine produced at the anode to react with the hydroxyl anion at the cathode, forming the hypochlorous anion, which is then further oxidized to chlorate, whether by oxidation at the anode or through... 

Solutions of available chlorine bleaches decompose on standing at a rate that depends on the conditions described below. Hypochlorous acid [7790-92-3] and hypochlorite anions decompose according to equations 6 and 7 (20,21) ... 

An acid that forms from a polyatomic anion whose name ends in -ite has a name ending in -ous. For example, HNO2 forms by adding a proton to the nitrite polyatomic anion, so HNO2 is nitrous acid. Likewise, HCIO is hypochlorous acid from the h T)ochlorite anion. 

The value of x is three orders of magnitude smaller than 0.67, so the approximation is valid. We know that the hypochlorite anion is the conjugate base of hypochlorous acid, so a pH > 7 is a reasonable result. 

Alpha-l-antiprotease (ai-AP) limits tissue damage arising from the actions of the leucocyte protease, elastase (Carrell and Travis, 1985), and there is much evidence available for the oxidative inactivation of this protein by oxygen-derived free-radical species and hypochlorous acid/hypochlorite anion (HOCl/OCP). The mechanism of this inactivation appears to involve the oxidation of a critical methionine residue (Met-358) to its corresponding sulphoxide and methionine sulphoxide has been detected in ai-AP samples isolated from the lungs of cigarette smokers (Carp et al., 1982) and rheumatoid synovial fluids (Wong and Travis, 1980). 

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). 

In addition to influencing the rate of a reaction, pH may also control the products where alternate or sequential pH-dependent reactions take place. An example of this type of reaction is the chlorination of phenol. Lee and Morris (37) have shown that the chlorination of phenol proceeds by the stepwise substitution at the 2, 4, and 6 positions of the aromatic ring. The rate of each of these reactions depends on the product of phenate or chlorophenate anion and the hypochlorous acid concentrations. Since each phenolic compound has a slightly different acid dissociation constant, the species of chlorophenols that are formed depend on the pH of the solution. 

Candeias LP, Patel KB, Stratford MRL, Wardman P (1993) Free hydroxyl radicals are formed on reaction between the neutrophil-derived species superoxide anion and hypochlorous acid. FEBS Lett 333 151-153... 

Fig. 7.3 Reactions showing the generation of ROS during lipid peroxidation and oxidative stress. Hydroxyl radical ( OH) lipid radical ( lipid), peroxyl radical (lipid-OO ) lipid peroxide (lipid-OOH) nitric oxide ( NO) nitrogen dioxide (N02) peroxynitrite anion (ONOO-) hypochlorous acid (HOC1), and hydrogen peroxide (H202)...

Oxidation of oxalic acid with dimethyl-V,V-dichlorohydantoin and dichloroisocya-nuric acid is of first order with respect to the oxidant. The order with respect to the reductant is fractional. The reactions are catalysed by Mn(II). Suitable mechanisms are proposed.129 A mechanism involving synchronous oxidative decarboxylation has been suggested for the oxidation of a-amino acids with l,3-dichloro-5,5-dimethylhydantoin.130 Kinetic parameters have been determined and a mechanism has been proposed for the oxidation of thiadiazole and oxadiazole with trichloroiso-cyanuric acid.131 Oxidation of two phenoxazine dyes, Nile Blue and Meldola Blue, with acidic chlorite and hypochlorous acid is of first order with respect to each of the reductant and chlorite anion. The rate constants and activation parameters for the oxidation have been determined.132... 

In the oxidation of alkanethiols to disulfides with chloramine-T (CAT), in alkaline solution, the proposed reactive species are hypochlorous acid and TsNCl- anion. A correlation of reaction rate with Taft s dual substituent parameter equation yielded p = -5.28 and 5 = -2.0, indicating the rate-enhancing effect of electron-donating substituents.133 Michaelis-Menten-type kinetics have been observed in the oxidation of atenolol with CAT in alkaline solutions. TsNHCl is assumed to be reactive species. A mechanism has been suggested and the activation parameters for the rate-determining step were calculated.134 The Ru(III)-catalysed oxidation of diphenyl... 

Hypochlorous acid and its anion are stronger oxidants than 02 and thus subject to decomposition in water. The only stable chlorine species in water is Cl-. 

The prefixes hypo- and per- remain as part of the acid name. For example, the acid of the perchlorate anion, CIO4", is perchloric acid, HCIO4. The acid of the hypochlorite anion, CIO", is hypochlorous acid, HCIO. 

Figure 27.10. Conversion of superoxide anion (02 ) to hydroxyl radical ( OH) in the presence of iron, or to hydrogen peroxide (H202) by superoxide dismutase (SOD), which is converted to hypochlorous acid by myeloperoxidase (MPO).

The addition of silver or mercury oxide precipitates the metal halide, leaving behind the aqueous solution, which is very reactive and is used for bleaching and sterilizing purposes. Solutions of hypohalites can be made by introducing the appropriate halogen into basic solutions (equation 113), but these will also contain some halide anions. To obtain pure hypochlorites, it is necessary to carefully neutralize pure hypochlorous acid. The most stable hypochlorites are those of Li, Ca, Sr, and Ba, although some others are also known but are not as stable, or are not sufficiently pure. 

The common denominator among the different chronic diseases that are hypothesized to be ameliorated by polyphenol intakes is oxidative stress. Polyphenols are believed to have antioxidant activity both in plants and in those that consume them. Tissue oxidants are produced by inflammatory cells. The first oxidant is superoxide anion radical (O2 ), generated by NADPH oxidase. This free radical is converted to hydrogen peroxide by superoxide dismutase. In activated neutrophils, hydrogen peroxide and chloride are converted to hypochlorous acid (HOCl) by the enzyme myeloperoxidase. ... 

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