Hypobromous acid

Hypobromous acid
Names
	IUPAC name hypobromous acid, bromic(I) acid, bromanol, hydroxidobromine
Identifiers
CAS Number	13517-11-8 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:29249 ;
ChemSpider	75379 ;
ECHA InfoCard	100.119.006
PubChem CID	83547;
UNII	GHT9BV419J ;
CompTox Dashboard (EPA)	DTXSID6021614 ;
	InChI InChI=1S/BrHO/c1-2/h2H Key: CUILPNURFADTPE-UHFFFAOYSA-N ; InChI=1S/BrHO/c1-2/h2H Key: CUILPNURFADTPE-UHFFFAOYSA-N; InChI=1/BrHO/c1-2/h2H Key: CUILPNURFADTPE-UHFFFAOYAL;
	SMILES OBr;
Properties
Chemical formula	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

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

{\ce {<=>>}}

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

{\ce {<=>>}}

HOBr + OH^-

Hypobromous acid has a pK_a 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.

3BrO⁻(aq) → 2Br⁻(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

Butler, Alison.; Walker, J. V. (1993). "Marine haloperoxidases". Chemical Reviews. 93 (5): 1937–1944. doi:10.1021/cr00021a014.
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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[1] Butler, Alison.; Walker, J. V. (1993). "Marine haloperoxidases". Chemical Reviews. 93 (5): 1937–1944. doi:10.1021/cr00021a014.

[titleEosinophils_preferentially_use_bromide_to_generate_halogenating_agents_--_Mayeno_et_al._264_(10):_5660_--_Journal_of_Biological_Chemistry-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.