Hypohalous

Hypohalous refers to a class of chemical species that contain the hypohalite functional group. In salts, this corresponds to the hypohalite anion XO−, where X is a halogen such as chlorine, bromine, or iodine. In the corresponding acids, the neutral hypohalous acids have the form HOX. The best-known example is hypochlorous acid HOCl, with related acids HOBr and HOI being studied and used to varying extents. These species are typically strong oxidants and play important roles in disinfection, bleaching, and oxidative chemistry.

Chemistry and examples

Hypohalites and hypohalous acids are derived from halogens reacting with water or protons in solution. Hypochlorous acid HOCl forms from chlorine gas in water, HOCl ⇌ H+ + OCl−, and can further equilibrate with hypochlorite in basic conditions to give the ClO− ion. Salts such as sodium hypochlorite NaOCl, sodium hypobromite NaOBr, and sodium hypoiodite NaOI exist and are used in various applications. The corresponding hypohalites are powerful oxidants and can react with acids to release halogen gases (for example, HOCl releasing Cl2 under strongly acidic conditions).

Reactions and properties

Hypohalites are capable of oxidizing organic and inorganic substrates. They may undergo disproportionation or conversion to higher-oxidation-state species (such as halates) under certain conditions, especially with changes in pH and temperature. In aqueous solutions, HOCl and related species are sometimes in dynamic equilibria with Cl−, ClO−, and Cl2, which underpins their practical use in disinfection and water treatment. Stability and reactivity vary with the halogen and the solution environment.

Applications and safety

Hypohalites are widely used as disinfectants and bleaching agents. Sodium hypochlorite solutions are common household bleaches and are used in water treatment, sanitation, and food processing. Hypohalous species can be corrosive and generate reactive oxygen species; they can release halogen gases when acidified, so handling requires appropriate safety precautions.

See also

Hypohalites

Hypohalous acids

Disinfection chemistry