Bromic acid

Bromic acid
Names
	IUPAC name Bromic acid
	Other names Bromic(V) acid; Hydrogen bromate
Identifiers
CAS Number	7789-31-3 ;
3D model (JSmol)	Interactive image; Interactive image;
ChEBI	CHEBI:49382 ;
ChEMBL	ChEMBL1161635 ;
ChemSpider	22853 ;
ECHA InfoCard	100.029.235
EC Number	232-158-3;
Gmelin Reference	25861
MeSH	Bromic+acid
PubChem CID	24445;
UNII	908X3OZ87J ;
CompTox Dashboard (EPA)	DTXSID7064861 ;
	InChI InChI=1S/BrHO3/c2-1(3)4/h(H,2,3,4) Key: SXDBWCPKPHAZSM-UHFFFAOYSA-N ; InChI=1/BrHO3/c2-1(3)4/h(H,2,3,4) Key: SXDBWCPKPHAZSM-UHFFFAOYAE;
	SMILES O[Br+2]([O-])[O-]; O=Br(=O)O;
Properties
Chemical formula	HBrO3
Molar mass	128.91 g/mol
Acidity (pKa)	−2
Conjugate base	Bromate
	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

Bromic acid, also known as hydrogen bromate, is an oxoacid with the molecular formula HBrO₃. It only exists in aqueous solution.[1][2] It is a colorless solution that turns yellow at room temperature as it decomposes to bromine.[1][3] Bromic acid and bromates are powerful oxidizing agents and are common ingredients in Belousov–Zhabotinsky reactions.[3][4] Belousov-Zhabotinsky reactions are a classic example of non-equilibrium thermodynamics.

Dissociation

Low concentrations dissociate completely to hydronium and bromate while high concentrations decompose to form bromine. Bromic acid's high instability can be explained because the positively charged hypervalent bromine is connected to the electronegative OH group.[5]

Structure

There are several isomers of HBrO₃.[5][6] The calculated bond lengths are listed below based on three high level theories G2MP2, CCSD(T), and QCISD(T).[5]

Species	HOOOBr	HOOBrO	HOBrO₂	HBrO₃
Br–O bridged (Å)	1.867	1.919	1.844	—
Br–O terminal (Å)	—	1.635	1.598	1.586

The large energy barriers between these structures do not make isomerization possible. HOBrO₂ is the most stable isomer and is the one pictured above.[6]

Synthesis

Bromic acid is the product of a reaction of barium bromate and sulfuric acid.[1]

Ba(BrO
₃)
₂ + H
₂SO
₄ → 2 HBrO
₃ + BaSO
₄

Barium sulfate is insoluble in water and forms a precipitate. The aqueous bromic acid can be decanted removing the barium sulfate.

References

The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals. 14th Edition. 2006.
Van Nostrand's Scientific Encyclopedia. Glenn D. Considine. Ninth Edition. Volume 1. p 554
Recipes for Belousov–Zhabotinsky reagents. J. Chem. Educ., 1991, 68 (4), 320. DOI: 10.1021/ed068p320
The Source of the Carbon Monoxide in the Classical Belousov–Zhabotinsky Reaction. J. Phys. Chem. A., 2007, 111 (32), 7805–12 DOI: 10.1021/jp073512+
Theoretical investigation of halogen-oxygen bonding and its implications in halogen chemistry and reactivity. Bioinorganic Chemistry and Applications, 2007, 1, 11/1–11/9
A Theoretical Examination of the Isomerization Pathways for HBrO3 Isomers. J. Phys. Chem. A, 2000, 104 (41), 9321-27. DOI: 10.1021/jp001604s

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[merck-1] The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals. 14th Edition. 2006.

[nostrand-2] Van Nostrand's Scientific Encyclopedia. Glenn D. Considine. Ninth Edition. Volume 1. p 554

[recipe-3] Recipes for Belousov–Zhabotinsky reagents. J. Chem. Educ., 1991, 68 (4), 320. DOI: 10.1021/ed068p320

[4] The Source of the Carbon Monoxide in the Classical Belousov–Zhabotinsky Reaction. J. Phys. Chem. A., 2007, 111 (32), 7805–12 DOI: 10.1021/jp073512+

[halogen-5] Theoretical investigation of halogen-oxygen bonding and its implications in halogen chemistry and reactivity. Bioinorganic Chemistry and Applications, 2007, 1, 11/1–11/9

[isomer-6] A Theoretical Examination of the Isomerization Pathways for HBrO3 Isomers. J. Phys. Chem. A, 2000, 104 (41), 9321-27. DOI: 10.1021/jp001604s