Hypobromous acid

Hypobromous acid is a weak, unstable acid with chemical formula of HOBr. It is mainly produced and handled in an aqueous solution. It is generated both biologically and commercially as a disinfectant. Salts of hypobromite are rarely isolated as solids.

Hypobromous acid
Names
IUPAC name
hypobromous acid, bromic(I) acid, bromanol, hydroxidobromine
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.119.006
UNII
Properties
HOBr
Molar mass 96.911
Density 2.470 g/cm3
Boiling point 20–25 °C (68–77 °F; 293–298 K)
Acidity (pKa) 8.65
Conjugate base Hypobromite
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Synthesis and properties

Addition of bromine to water gives hypobromous acid and hydrobromic acid (HBr) via a disproportionation reaction.

Br2 + H2O HOBr + HBr

In nature, hydrobromous acid is produced by bromoperoxidases, which are enzymes that catalyze the oxidation of bromide with hydrogen peroxide:[1]

Br− + H2O2 HOBr + OH−

Hypobromous acid has a pKa of 8.65 and is therefore only partially dissociated in water at pH 7. Like the acid, hypobromite salts are unstable and undergo a slow disproportionation reaction to yield the respective bromate and bromide salts.

3 BrO−(aq) → 2 Br−(aq) + BrO−
3(aq)

Its chemical and physical properties are similar to those of other hypohalites.

Uses

HOBr is used as a bleach, an oxidizer, a deodorant, and a disinfectant, due to its ability to kill the cells of many pathogens. The compound is generated in warm-blooded vertebrate organisms especially by eosinophils, which produce it by the action of eosinophil peroxidase, an enzyme which preferentially uses bromide.[2] Bromide is also used in hot tubs and spas as a germicidal agent, using the action of an oxidizing agent to generate hypobromite in a similar fashion to the peroxidase in eosinophils. It is especially effective when used in combination with its congener, hypochlorous acid.

References
  1. Butler, Alison.; Walker, J. V. (1993). "Marine haloperoxidases". Chemical Reviews. 93 (5): 1937–1944. doi:10.1021/cr00021a014.
  2. Mayeno, AN; Curran, AJ; Roberts, RL; Foote, CS (1989). "Eosinophils preferentially use bromide to generate halogenating agents". The Journal of Biological Chemistry. 264 (10): 5660–8. PMID 2538427. Retrieved 2008-01-12.
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