Hypobromous acid
Space-filling model of hypobromous acid
IUPAC name
hypobromous acid, bromic(I) acid, bromanol, hydroxidobromine
3D model (JSmol)
ECHA InfoCard 100.119.006 Edit this at Wikidata
  • InChI=1S/BrHO/c1-2/h2H checkY
  • InChI=1S/BrHO/c1-2/h2H
  • InChI=1/BrHO/c1-2/h2H
  • OBr
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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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.

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, hypobromous acid is produced by bromoperoxidases, which are enzymes that catalyze the oxidation of bromide with hydrogen peroxide:[1][2]

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

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


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.[3] 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.


  1. ^ Ximenes, V. F., Morgon, N. H., & de Souza, A. R. (2015). Hypobromous acid, a powerful endogenous electrophile: Experimental and theoretical studies. Journal of inorganic biochemistry, 146, 61-68.
  2. ^ Butler, Alison.; Walker, J. V. (1993). "Marine haloperoxidases". Chemical Reviews. 93 (5): 1937–1944. doi:10.1021/cr00021a014.
  3. ^ 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. doi:10.1016/S0021-9258(18)83599-2. PMID 2538427. Archived from the original on 2009-05-26. Retrieved 2008-01-12.