hypochlorous+acid


 * Hypochlorous acid** is a weak acid with the chemical formula HClO. It forms when chlorine dissolves in water. It cannot be isolated in pure form due to rapid equilibration with its precursor. HClO is an oxidizer, and as its sodium salt sodium hypochlorite, (NaClO), or its calcium salt calcium hypochlorite, (Ca(CIO) 2 ) is used as a bleach a deodorant, and a disinfectant.

in organic synthesis, HClO converts to alkenes to chlorohydrins. In biology, acid is generated in activated neutrophils by myelperoxidase-mediated peroxidation of chloride ions, and contributes to the destruction of bacteria. In water treatment, this acid is the active sanitizer in hypochlorite-based products. (Swimming pools). In food services, and water distribution, specialized equipment to generate weak solutions of HOCl form water and salt sometimes is used to generate adequate quantities of __safe__ (unstable) disinfectant to treat food preparation surfaces and water supplies. In bleaching, hypochlorous acid acts to oxidize the agents which cause stains. This strong oxidating power can also make the chemical very dangerous, because it can become explosive in certain settings. Adding acids to a hypochlorous acid solution will precipitate this __process__, making the mixture unstable, releasing chlorine gas, and potentially causing an explosive chemical reaction.
 * ~ ===Uses===



In disinfecting, a solution with a pH __balance__ of around five to six is usually optimal. The compound needs to be handled carefully because it can release dangerous chlorine gas if it is mixed with the wrong chemicals. Chlorine gas can cause considerable health problems or death, especially in a space which is poorly ventilated, which is one reason why it is inadvisable to mix household chemicals at random.  Hypochlorous acid should be stored in a sealed container in a cool dry place out of the reach of children and pets. It is a good idea to mark the container to make sure that people are aware of the contents, and to add a warning that it should not be used with acids.

Hypochlorous acid ||
 * [[image:http://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/Hypochlorous-acid-2D-dimensions.svg/150px-Hypochlorous-acid-2D-dimensions.svg.png width="210" height="127" link="http://en.wikipedia.org/wiki/File:Hypochlorous-acid-2D-dimensions.svg"]] ||
 * [[image:http://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Hypochlorous-acid-3D-vdW.png/150px-Hypochlorous-acid-3D-vdW.png width="195" height="151" link="http://en.wikipedia.org/wiki/File:Hypochlorous-acid-3D-vdW.png"]] ||
 * Other names:Hydrogen hypochlorite, Chlorine hydroxide ||
 * Other names:Hydrogen hypochlorite, Chlorine hydroxide ||

Formation, stability and reactions
Addition of chlorine to water gives both hydrochloric acid (HCl) and hypochlorous acid:[8 ] Cl2 + H2O HClO + HCl When acids are added to aqueous salts of hypochlorous acid (such as sodium hypochlorite in commercial bleach solution), the resultant reaction is driven to the left, and chlorine gas is evolved. Thus, the formation of stable hypochlorite bleaches is facilitated by dissolving chlorine gas into basic water solutions, such as sodium hydroxide. The acid can also be prepared by dissolving dichlorine monoxide in water; under standard aqueous conditions, anhydrous hypochlorous acid is impossible to prepare due to the readily reversible equilibrium between it and its anhydride [9 ] : 2 HOCl Cl2O + H2O K(0°C) = 3.55×10−3 dm3mol−1 The presence of light or transition metal oxides of copper, nickel, or cobalt accelerates the exothermic decomposition into hydrochloric acid and oxygen:[9 ] 2 Cl2 + 2 H2O → 4 HCl + O2

Chemical reactions
In aqueous solution, hypochlorous acid partially dissociates into the anion //hypochlorite// OCl−: HClO OCl− + H+  [|Salts] of hypochlorous acid are called hypochlorites. One of the best-known hypochlorites is NaClO, the active ingredient in bleach. HClO is a stronger oxidant than chlorine under standard conditions. 2 HClO(//aq//) + 2 H+ + 2 //e//− Cl2(//g//) + 2 H2O E = +1.63 V  HClO reacts with HCl to form chlorine gas: HClO + HCl → H2O + Cl2

** Reaction with protein sulfhydryl groups **
Knox //et al.// [|[23]] first noted that HClO is a sulfhydryl inhibitor that, in sufficient quantity, could completely inactivate proteins containing sulfhydryl groups. This is because HClO oxidises sulfhydryl groups, leading to the formation of disulfide bonds [26 ] that can result in crosslinking of proteins. The HClO mechanism of sulfhydryl oxidation is similar to that of chloramine, and may only be bacteriostatic, because, once the residual chlorine is dissipated, some sulfhydryl function can be restored. [|[22]] One sulfhydryl-containing amino acid can scavenge up to four molecules of HOCl. [|[25]] Consistent with this, it has been proposed that sulfhydryl groups of sulfur-containing amino acid can be oxidized a total of three times by three HClO molecules, with the fourth reacting with the α-amino group. The first reaction yields sulfenic acid (R-SOH) then sulfinc acid (R-SO2H) and finally R-SO3H. Each of those intermediates can also condense with another sulfhydryl group, causing cross-linking and aggregation of proteins. Sulfinic acid and R-SO3H derivatives are produced only at high molar excesses of HClO, and disulfides are formed primarily at bacteriocidal levels. [|[12]] Disulfide bonds can also be oxidized by HClO to sulfinic acid. [|[26]] Because the oxidation of sulfhydryls and [|disulfides] evolves [|hydrochloric acid], [|[12]] this process results in the depletion HClO.

** Reaction with protein amino groups **
Hypochlorous acid reacts readily with amino acids that have [|amino group] side-chains, with the chlorine from HClO displacing a hydrogen, resulting in an organic chloramine. [|[27]] Chlorinated [|amino acids] rapidly decompose, but [|protein] chloramines are longer-lived and retain some oxidative capacity. [|[4]][|[25]] Thomas //et al.// [|[4]] concluded from their results that most organic chloramines decayed by internal rearrangement and that fewer available [|NH 2] groups promoted attack on the [|peptide bond], resulting in cleavage of the [|protein]. McKenna and Davies [|[28]] found that 10 mM or greater HClO is necessary to fragment proteins in vivo. Consistent with these results, it was later proposed that the chloramine undergoes a molecular rearrangement, releasing [|HCl] and [|ammonia] to form an [|amide]. [|[29]] The [|amide group] can further react with another [|amino group] to form a [|Schiff base], causing cross-linking and aggregation of proteins. [|[16]]

** Reaction with DNA and nucleotides **
Hypochlourous acid reacts slowly with DNA and RNA as well as all nucleotides in vitro. [|[10]][|[30]] [|GMP] is the most reactive because HClO reacts with both the heterocyclic NH group and the amino group. In similar manner, [|TMP] with only a heterocyclic NH group that is reactive with HClO is the second-most reactive. [|AMP] and [|CMP], which have only a slowly reactive amino group, are less reactive with HClO. [|[30]] [|UMP] has been reported to be reactive only at a very slow rate. [|[5]][|[10]] The heterocyclic NH groups are more reactive than amino groups, and their secondary chloramines are able to donate the chlorine. [|[12]] These reactions likely interfere with DNA base pairing, and, consistent with this, Prütz [|[30]] has reported a decrease in viscosity of DNA exposed to HClO similar to that seen with heat denaturation. The sugar moieties are nonreactive and the DNA backbone is not broken. [|[30]] NADH can react with chlorinated TMP and UMP as well as HClO. This reaction can regenerate UMP and TMP and results in the 5-hydroxy derivative of NADH. The reaction with TMP or UMP is slowly reversible to regenerate HClO. A second slower reaction that results in cleavage of the pyridine ring occurs when excess HClO is present. NAD+ is inert to HClO. [|[12]][|[30]] ** Reaction with lipids ** Hypochlorous acid reacts with [|unsaturated bonds] in [|lipids], but not [|saturated bonds] , and the [|OCl−] ion does not participate in this reaction. This reaction occurs by [|hydrolysis] with addition of [|chlorine] to one of the carbons and a [|hydroxyl] to the other. The resulting compound is a chlorhydrin. [|[13]] The polar chlorine disrupts [|lipid bilayers] and could increase permeability. [|[14]] When chlorhydrin formation occurs in lipid bilayers of red blood cells, increased permeability occurs. Disruption could occur if enough chlorhydrin is formed. [|[13]][|[19]] The addition of preformed chlorhydrins to red blood cells can affect permeability as well. [|[15]] [|Cholesterol] chlorhydrins have also been observed, [|[14]][|[17]] but do not greatly affect permeability, and it is believed that [|Cl2] is responsible for this reaction. [|[17]]