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	{{chembox		{{chembox
	| verifiedrevid = 443428416		| verifiedrevid = 443429816
	| ImageFile = Bromige saeure.png		| ImageFile = Bromige saeure.png
	| ImageSize =		| ImageSize =
			| ImageFile2 = Bromous_acid_molecule_ball.png
			| ImageSize2 = 160
			| ImageFile1 = Bromous acid molecule spacefill.png
			| ImageSize1 = 160
			| ImageAlt1 = Space-filling model of the bromous acid molecule
			| ImageAlt2 = Ball and stick model of the bromous acid molecule
	| IUPACName = hydroxy-λ<sup>3</sup>-bromanone<br />hydroxidooxidobromine<br />bromous acid		| IUPACName = hydroxy-λ<sup>3</sup>-bromanone<br />hydroxidooxidobromine<br />bromous acid
		⚫	|Section1={{Chembox Identifiers
	| OtherNames =
			| CASNo =37691-27-3
⚫	| Section1 = {{Chembox Identifiers
	| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}		| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
	| ChemSpiderID = 145144		| ChemSpiderID = 145144
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	| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}		| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
	| StdInChIKey = DKSMCEUSSQTGBK-UHFFFAOYSA-N		| StdInChIKey = DKSMCEUSSQTGBK-UHFFFAOYSA-N
	| CASNo =
	| PubChem = 165616		| PubChem = 165616
	| ChEBI_Ref = {{ebicite|correct|EBI}}		| ChEBI_Ref = {{ebicite|correct|EBI}}
	| ChEBI = 29247		| ChEBI = 29247
	| SMILES = O=BrO		| SMILES = O
	}}		}}
	| Section2 = {{Chembox Properties		|Section2={{Chembox Properties
	| Formula = HBrO<sub>2</sub>		| Formula = HBrO<sub>2</sub>
	| MolarMass = 112.911 g/mol		| MolarMass = 112.911 g/mol
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	| MeltingPt =		| MeltingPt =
	| BoilingPt =		| BoilingPt =
	| Solubility = }}		| Solubility =
			| ConjugateBase = Bromite}}
	| Section3 = {{Chembox Hazards		|Section3={{Chembox Hazards
	| MainHazards =		| MainHazards =
	| FlashPt =		| FlashPt =
	| Autoignition = }}		| AutoignitionPt = }}
	| Section4 = {{Chembox Other		|Section4={{Chembox Related
	| OtherAnions = ]; ]; ]; ]}}		| OtherAnions = ]; ]; ]; ]}}
	}}		}}
	'''Bromous acid''' with the formula HBrO<sub>2</sub> has bromine in the +3 ]. The salts of bromous acid are called bromites. The acid is not stable and only occurs as an intermediate, for example in the oxidation of ]s.<ref name = "Wiberg&Holleman">Egon Wiberg, Arnold Frederick Holleman (2001) ''Inorganic Chemistry'', Elsevier ISBN 0-12-352651-5</ref>		'''Bromous acid''' is the ] with the formula of HBrO<sub>2</sub>. It is an unstable compound, although salts of its conjugate base – bromites – have been isolated. In acidic solution, bromites decompose to bromine.<ref name="Wiberg&Holleman">{{cite book |chapter=Oxygen Acids of Bromine |pages=449–451 |chapter-url={{GBurl|Mtth5g59dEIC|p=449}} |editor1-first=Nils |editor1-last=Wiberg |editor2-first=A. F. |editor2-last=Holleman |editor3-first=Egon |editor3-last=Wiberg |title=Inorganic Chemistry |date=2001 |publisher=Academic Press |isbn=978-0-12-352651-9 }}</ref>
	== Chemistry ==		== Discovery ==
			In 1905, Richards A. H. proved the existence of bromous acid through a series of experiments involving ] (AgNO<sub>3</sub>) and bromine.<ref name=":3">{{cite journal |last1=Richards |first1=A. H. |title=The existence of bromous acid ({{chem|H|Br|O|2}}) |journal=Journal of the Society of Chemical Industry |volume=25 |issue=1 Suppl |date=15 January 1906 |pages=4–5 |hdl=2027/mdp.39015030318508?urlappend=%3Bseq=144%3Bownerid=13510798902008078-170 |hdl-access=free }}</ref> The reaction of excess cold aqueous to form ] (HBrO), ] (AgBr) and ] (HNO<sub>3</sub>):
	Bromous acid can be produced by classical chemical or electrochemicals method via ] oxidation.{{Fact|date=January 2009}}
			:Br<sub>2</sub> + AgNO<sub>3</sub> + H<sub>2</sub>O → HBrO + AgBr + HNO<sub>3</sub>
			Richards discovered that the effect of adding excess liquid bromine in a concentrated ] (AgNO<sub>3</sub>) resulted in a different reaction mechanism. From numbers of equivalent portions of acid bromine formed from the previous reaction, the ratio between oxygen and bromine was calculated, with the exact value of O:Br (0.149975:0.3745), suggesting the acid compound contains two oxygen atom to one bromine atom. Thus, the chemical structure of the acid compound was deducted as HBrO<sub>2</sub>.<ref name=":3" />
			According to Richards, ] (HBrO) arises by the reaction of bromine and silver nitrate solution:<ref name=":3" />
⚫	:HBrO + HClO &rarr; HBrO<sub>2</sub> + HCl
			:Br<sub>2</sub> + AgNO<sub>3</sub> + H<sub>2</sub>O → HBrO + AgBr + HNO<sub>3</sub>
			:2&nbsp;AgNO<sub>3</sub> + HBrO + Br<sub>2</sub> + H<sub>2</sub>O → HBrO<sub>2</sub> + 2&nbsp;AgBr + 2 HNO<sub>3</sub>
			== Isomerism ==
	Also disproportioning of hypobromous acid will give bromous acid and ].{{Fact|date=January 2009}}
			The molecule HBrO<sub>2</sub> has a bent structure with ∠(H−O−Br) angles of 106.1°. HOBrO also adopts a non-planar conformation with one isomer structure (2a) adopting a dihedral angle ∠(H−O−Br−O) of 74.2°. Moreover, the planar structures of two other isomers (2b-''cis'' and 2c-''trans'') are transition state for fast enantiomerization.<ref>{{cite journal |last1=Glaser |first1=Rainer |last2=Jost |first2=Mary |title=Disproportionation of Bromous Acid HOBrO by Direct O-Transfer and via Anhydrides O(BrO)<sub>2</sub> and BrO-BrO<sub>2</sub>. An Ab Initio Study of the Mechanism of a Key Step of the Belousov–Zhabotinsky Oscillating Reaction |journal=The Journal of Physical Chemistry A |date=16 August 2012 |volume=116 |issue=32 |pages=8352–8365 |doi=10.1021/jp301329g |pmid=22871057 |bibcode=2012JPCA..116.8352G }}</ref>
			<!-- Deleted image removed: ] -->
			Another study identified three isomers: HOOBr, HOBrO, and HBr(O)O.<ref>{{cite journal |last1=de Souza |first1=Gabriel L. C. |last2=Brown |first2=Alex |title=The ground and excited states of HBrO<sub>2</sub> and HBrO<sub>3</sub> (HOOOBr and HOOBrO) isomers |journal=Theoretical Chemistry Accounts |date=July 2016 |volume=135 |issue=7 |doi=10.1007/s00214-016-1931-8 }}</ref>
⚫	:2 HBrO &rarr; HBrO<sub>2</sub> + HBr
			<!-- Deleted image removed: ] -->
			== Synthesis ==
	Lastly, a synproportion reaction of bromic acid and hydrobromic acid gives bromous acid.{{Fact|date=January 2009}}
			A oxidation reaction between ] (HBrO) and ] (HClO) can be used to produce bromous acid (HBrO<sub>2</sub>) and ] (HCl).{{cn|date=September 2023}}
		⚫	:HBrO + HClO → HBrO<sub>2</sub> + HCl
			A redox reaction of ] (HBrO) can form bromous acid (HBrO<sub>2</sub>) as its product:{{cn|date=September 2023}}
⚫	:2 HBrO<sub>3</sub> + HBr &rarr; 3 HBrO<sub>2</sub>
			:HBrO + H<sub>2</sub>O − 2e<sup>−</sup> → HBrO<sub>2</sub> + 2H<sup>+</sup>
			The ] of two equivalents ] (HBrO) results in the formation of both bromous acid (HBrO<sub>2</sub>) and ] (HBr):{{cn|date=September 2023}}
	==Compounds==
		⚫	: 2&nbsp;HBrO → HBrO<sub>2</sub> + HBr
			A rearrangement reaction, which results from the syn-proportion of ] (HBrO<sub>3</sub>) and ] (HBr) gives bromous acid (HBrO<sub>2</sub>):{{cn|date=September 2023}}
	Several bromites are stable and have been isolated. For example NaBrO<sub>2</sub>· 3H<sub>2</sub>O and Ba(BrO<sub>2</sub>)<sub>2</sub>·H<sub>2</sub>O.<ref name = "Wiberg&Holleman"/>
		⚫	:2&nbsp;HBrO<sub>3</sub> + HBr → 3&nbsp;HBrO<sub>2</sub>
	==Use==		==Salts==
			]
			The salts ] and ] have been crystallized. Upon treatment of these aqueous solutions with salts of Pb<sup>2+</sup>, Hg<sup>2+</sup>, and Ag<sup>+</sup>, the corresponding heavy metal bromites precipitate as solids.<ref name = "Wiberg&Holleman"/>
			== Belousov–Zhabotinsky reaction ==
⚫	Bromites can be used for the reduction of ]s to ]s.<ref name = "Wiberg&Holleman"/>
			Bromous acid is a product of the ] resulting from the combination of potassium bromate, cerium(IV) sulfate, propanedioic acid and citric acid in dilute sulfuric acid. Bromous acid is an intermediate stage of the reaction between bromate ion ({{chem|BrO|3|−}} ) and bromine (Br<sup>−</sup>):<ref name=":0">{{cite journal |last1=Vassalini |first1=Irene |last2=Alessandri |first2=Ivano |title=Spatial and Temporal Control of Information Storage in Cellulose by Chemically Activated Oscillations |journal=ACS Applied Materials & Interfaces |date=30 December 2015 |volume=7 |issue=51 |pages=28708–28713 |doi=10.1021/acsami.5b11857 |pmid=26654462 |url=https://figshare.com/articles/journal_contribution/2093821 }}</ref><ref name=":1">{{cite journal |last1=Field |first1=Richard J. |last2=Koros |first2=Endre |last3=Noyes |first3=Richard M. |title=Oscillations in chemical systems. II. Thorough analysis of temporal oscillation in the bromate-cerium-malonic acid system |journal=Journal of the American Chemical Society |date=December 1972 |volume=94 |issue=25 |pages=8649–8664 |doi=10.1021/ja00780a001 |bibcode=1972JAChS..94.8649F }}</ref>
			* {{chem|BrO|3|−}} + 2&nbsp;Br<sup>−</sup> → HBrO<sub>2</sub> + HBrO
			Other relevant reactions in such oscillating reactions are:
⚫	:2MnO{{su|b=4|p=−}} + BrO{{su|b=2|p=−}} + OH<sup>−</sup> → 2MnO{{su|b=4|p=2−}} + BrO{{su|b=3|p=−}} + H<sub>2</sub>O
			* HBrO<sub>2</sub> + {{chem|BrO|3|−}} + H<sup>+</sup> → 2&nbsp;{{chem|BrO|2|•}} + H<sub>2</sub>O
			* 2&nbsp;HBrO<sub>2</sub> → {{chem|BrO|3|−}} + HOBr + H<sup>+</sup>
		⚫	Bromites reduce ]s to ]s (VI):<ref name="Wiberg&Holleman" />
		⚫	* 2&nbsp;{{chem|MnO|4|−}} + {{chem|BrO|2|−}} + OH<sup>−</sup> → 2&nbsp;{{chem|MnO|4|2−}} + {{chem|BrO|3|−}} + H<sub>2</sub>O
			== p''K''<sub>a</sub> measurement ==
			The acid dissociation constant of bromous acid, ''K''<sub>a</sub> = <big>{{sfrac||}}</big>, was determined using different methods.
			The value of the p''K''<sub>a</sub> for bromous acid was estimated in research studying the decomposition of bromites. The research measured the rate of bromite decomposition as a function of hydrogen and bromite ion concentrations. The experimental data of the log of the initial velocity were plotted against pH. Using this method, the estimated p''K''<sub>a</sub> value for bromous acid was 6.25.<ref>{{cite journal |last1=Massagli |first1=A. |last2=Indelli |first2=A. |last3=Pergola |first3=F. |title=Kinetic investigation of the decomposition of bromite |journal=Inorganica Chimica Acta |date=1970 |volume=4 |pages=593–596 |doi=10.1016/S0020-1693(00)93357-7 }}</ref>
			Using another method, the pK<sub>a</sub> for bromous acid was measured based on the initial velocity of the reaction between sodium bromites and potassium iodine in a pH range of 2.9–8.0, at 25&nbsp;°C and ionic strength of 0.06&nbsp;M. The first order dependence of the initial velocity of this ] on in a pH range of 4.5–8.0. The value of acid dissociation constant measured by this method is ''K''<sub>a</sub> = {{val|3.7|0.9|e=-4|u=M}} and p''K''<sub>a</sub> = {{val|3.43|0.05}}.<ref>{{cite journal |last1=Faria |first1=R. B. |last2=Epstein |first2=Irving R. |last3=Kustin |first3=Kenneth |title=Kinetics of Disproportionation and pKa of Bromous Acid |journal=The Journal of Physical Chemistry |date=January 1994 |volume=98 |issue=4 |pages=1363–1367 |doi=10.1021/j100055a051 }}</ref>
			== Reactivity ==
			In comparison to other oxygen-centered oxidants (hypohalites, anions of peroxides) and in line with its low basicity, bromite is a rather weak nucleophile.<ref>{{cite journal |last1=Mayer |first1=Robert J. |last2=Ofial |first2=Armin R. |title=Nucleophilic Reactivities of Bleach Reagents |journal=Organic Letters |date=18 May 2018 |volume=20 |issue=10 |pages=2816–2820 |doi=10.1021/acs.orglett.8b00645 |pmid=29741385 }}</ref> Rate constants of bromite towards carbocations and acceptor-substituted olefins are by 1–3 orders of magnitude lower than the ones measured with hypobromite.
	==References==		==References==
	{{reflist}}		{{reflist}}
			==Further reading==
			* {{cite book |doi=10.1002/0471238961.0218151321110512.a01 |chapter=Bromine, Inorganic Compounds |title=Kirk-Othmer Encyclopedia of Chemical Technology |date=2002 |last1=Ukeles |first1=S.D. |last2=Freiberg |first2=M. |isbn=978-0-471-48494-3 }}
	{{Hydrogen compounds}}		{{Hydrogen compounds}}
	]		]
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	]
	{{Inorganic-compound-stub}}
	]
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