Hypochlorite

In chemistry, hypochlorite is an ion with the chemical formula ClO−. It combines with a number of cations to form hypochlorites, which may also be regarded as the salts of hypochlorous acid. Common examples include sodium hypochlorite (household bleach) and calcium hypochlorite (a component of bleaching powder, swimming pool 'chlorine'). In chemistry, hypochlorite is an ion with the chemical formula ClO−. It combines with a number of cations to form hypochlorites, which may also be regarded as the salts of hypochlorous acid. Common examples include sodium hypochlorite (household bleach) and calcium hypochlorite (a component of bleaching powder, swimming pool 'chlorine'). The name can also refer to esters of the hypothetical hypochlorous acid, namely organic compounds with a ClO– group covalently bound to the rest of the molecule. Examples include methyl hypochlorite and t-butyl hypochlorite. Most hypochlorite salts are unstable in their pure forms, and are normally handled as aqueous solutions. Their primary applications are as bleaching, disinfection, and water treatment agents but they are also used in chemistry for chlorination and oxidation reactions. Acidification of hypochlorites generates hypochlorous acid. This exists in an equilibrium with chlorine gas, which can bubble out of solution. The equilibrium is subject to Le Chatelier's principle; thus a high pH drives the reaction to the left by consuming H+ ions, promoting the disproportionation of chlorine into chloride and hypochlorite, whereas a low pH drives the reaction to the right, promoting the release of chlorine gas. Hypochlorous acid also exists in equilibrium with its anhydride; dichlorine monoxide. Hypochlorites are generally unstable and many compounds exist only in solution. Only lithium hypochlorite LiOCl, calcium hypochlorite Ca(OCl)2 and barium hypochlorite Ba(ClO)2 have been isolated as pure anhydrous compounds, all of which are solids. A few more can be produced as aqueous solutions. In general the greater the dilution the greater their stability. The hypochlorite ion is unstable with respect to disproportionation. Upon heating, it degrades to a mixture of chloride, oxygen and other chlorates: This reaction is exothermic and in the case of concentrated hypochlorites, such as LiOCl and Ca(OCl)2, can lead to a dangerous thermal runaway and potentially explosions. The alkali metal hypochlorites decrease in stability down the group. Anhydrous lithium hypochlorite is stable at room temperature; however, sodium hypochlorite has not be prepared drier than the pentahydrate (NaOCl·(H2O)5). This is unstable above 0 °C; although the more dilute solutions encountered as household bleach possesses better stability. Potassium hypochlorite (KOCl) is known only in solution.