The hypobromite

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

, also called alkaline

bromine Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...

water, is BrO⁻. Bromine is in the +1

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons ...

. The Br–O bond length is 1.82 Å. Hypobromite is the bromine compound analogous to

hypochlorite In chemistry, hypochlorite, or chloroxide is an oxyanion with the chemical formula ClO−. It combines with a number of cations to form hypochlorite salts. Common examples include sodium hypochlorite (household bleach) and calcium hypochlorite ...

s found in common bleaches, and in immune cells. In many ways, hypobromite functions in the same manner as hypochlorite, and is also used as a germicide and antiparasitic in both industrial applications, and in the immune system.

Preparation

Hypobromite salts form upon treating bromine with aqueous alkali, such as sodium or potassium hydroxide. At 20 °C the reaction is rapid. : Br₂ + 2 OH⁻(aq) → Br⁻ + BrO⁻ + H₂O In this reaction the bromine

disproportionates In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation state. The reverse of disproportionatio ...

(some undergoes reduction and some oxidation) from oxidation state 0 (Br₂) to oxidation state −1 (Br⁻) and oxidation state +1 (BrO⁻).

Sodium hypobromite Sodium hypobromite is an inorganic compound with the chemical formula . It is a sodium salt of hypobromous acid. It consists of sodium cations and hypobromite anions . It is usually obtained as the pentahydrate, so the compound that is usually c ...

can be isolated as an orange solid. A secondary reaction, where hypobromite spontaneously disproportionates to

bromide A bromide ion is the negatively charged form (Br−) of the element bromine, a member of the halogens group on the periodic table. Most bromides are colorless. Bromides have many practical roles, being found in anticonvulsants, flame-retard ...

(bromine oxidation state −1) and

bromate The bromate anion, , is a bromine-based oxoanion. A bromate is a chemical compound that contains this ion. Examples of bromates include sodium bromate () and potassium bromate (). Bromates are formed many different ways in municipal drinking w ...

(bromine oxidation state +5) takes place rapidly at 20 °C and slowly at 0 °C. : 3 BrO⁻ → 2 Br⁻ + Hence, in reaction 2, the formation and proportions of the −1, +1 and +5 bromine oxidation state products can be controlled by temperature. Hypobromite is not thermodynamically stable at any pH (see Pourbaix diagram for bromine at http://www.eosremediation.com/download/Chemistry/Chemical%20Properties/Eh_pH_Diagrams.pdf ), but it is kinetically locked toward a further disproportion into bromate and bromide above the pKa of HBrO. These reactions of bromine are analogous to those of chlorine forming

and

chlorate Chlorate is the common name of the anion, whose chlorine atom is in the +5 oxidation state. The term can also refer to chemical compounds containing this anion, with Chlorate#Compounds (salts), chlorates being the salt (chemistry), salts of chlo ...

. The corresponding chlorine reaction 1 (to form ClO⁻) is fast at 20 °C and reaction 2 (to form ) is slow at 20 °C and fast at 70 °C.

Compounds

A hypobromite is a compound that contains this anion. Examples include

sodium hypobromite Sodium hypobromite is an inorganic compound with the chemical formula . It is a sodium salt of hypobromous acid. It consists of sodium cations and hypobromite anions . It is usually obtained as the pentahydrate, so the compound that is usually c ...

and

potassium hypobromite Potassium is a chemical element; it has symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to form flaky white pot ...

In nature and industry

Bromide from the diet, naturally present in the blood, is used by

eosinophils Eosinophils, sometimes called eosinophiles or, less commonly, acidophils, are a variety of white blood cells and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. Along wi ...

, white blood cells of the granulocyte class, specialized for dealing with multi-cellular parasites. These cells react the bromide with peroxide to generate hypobromite by the action of

eosinophil peroxidase Eosinophil peroxidase is an enzyme found within the eosinophil granulocytes, innate immune cells of humans and mammals. This oxidoreductase protein is encoded by the gene ''EPX'', expressed within these myeloid cells. EPO shares many similarities ...

, a

haloperoxidase Haloperoxidases are peroxidases that are able to mediate the oxidation of halides by hydrogen peroxide. Both halides and hydrogen peroxide are widely available in the environment. Mechanistic and thermodynamic considerations Halogenations of orga ...

enzyme which preferentially uses bromide over chloride for this purpose. Simple bromide salts (such as sodium bromide) are also sometimes used in

hot tub A hot tub is a large tub full of water used for hydrotherapy, relaxation or pleasure. Some have powerful jets for massage purposes. Hot tubs are sometimes also known as "spas" or by the trade name Jacuzzi. Hot tubs may be located outdoors or ...

s and spas as mild germicidal agents, using the action of an added oxidizing agent (such as hydrogen peroxide) to generate ''in situ'' hypobromite, in a similar fashion to the action of peroxidase on bromide in eosinophils. Hypobromite has been proposed to be a reactive intermediate in the

Hofmann rearrangement The Hofmann rearrangement (Hofmann degradation) is the organic reaction of a primary amide to a primary amine with one less carbon atom. The reaction involves oxidation of the nitrogen followed by rearrangement of the carbonyl and nitrogen to gi ...

References

{{reflist Hypobromites

Preparation

Compounds

In nature and industry

See also

References