hypoiodous acid

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| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 477003468

| ImageFile1 = Hypoiodige-Säure.png

| ImageFileL1 = Hypoiodous-acid-3D-vdW.png

| ImageCaptionL1 = {{legend|white|Hydrogen, H}}{{legend|red|Oxygen, O}}{{legend|rgb(128, 0, 104)|Iodine, I}}

| ImageFileR1 = Hypoiodous-acid-3D-balls.png

| IUPACName = Hypoiodous acid

| OtherNames =

|Section1={{Chembox Identifiers

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 109942

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChI = 1S/HIO/c1-2/h2H

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = GEOVEUCEIQCBKH-UHFFFAOYSA-N

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo = 14332-21-9

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 2PYC923C5W

| PubChem = 123340

| RTECS =

| ChEBI_Ref = {{ebicite|correct|EBI}}

| ChEBI = 29231

| SMILES = IO}}

|Section2={{Chembox Properties

| Formula = HOI

| H=1|I=1|O=1

| Appearance =

| Density =

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| BoilingPt_notes =

| pKa = 10.5 (in water, estimate){{cite book|title=Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution|editor-first=D. D.|editor-last=Perrin|edition=2nd|series=IUPAC Chemical Data|issue=29|publisher=Pergamon|location=Oxford|year=1982|publication-date=1984|orig-date=1969|lccn=82-16524|isbn=0-08-029214-3|at=Entry 119}}

| Viscosity =

| ConjugateBase = Hypoiodite

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|Section7={{Chembox Hazards

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|Section9={{Chembox Related

| OtherCompounds = {{ubl|Hypofluorous acid|Hypochlorous acid|Hypobromous acid}}

}}

}}

Hypoiodous acid is an inorganic compound with the chemical formula {{chem2|HIO|auto=1}}. It forms when an aqueous solution of iodine is treated with mercuric or silver salts. It rapidly decomposes by disproportionation:{{cite book|last1=Holleman|first1=A.F.|title=Inorganic chemistry|date=2001|publisher=Academic Press, W. de Gruyter.|location=San Diego, Calif. : Berlin|isbn=0-12-352651-5|edition=1st English|editor-first=Nils|editor-last=Wiberg}}

:{{chem2|5 HIO → HIO3 + 2 I2 + 2 H2O}}

Hypoiodous acid is a weak acid with a pK_a of about 11. The conjugate base is hypoiodite ({{chem2|IO−}}). Salts of this anion can be prepared by treating iodine with alkali hydroxides. They rapidly disproportionate to form iodides and iodates, but an iodine–hydroxide mixture can be used an in situ preparation of hypoiodite for other reactions.{{cite journal |doi=10.1021/ja01308a043 |title=The Haloform Reaction. XVI. The Action of Hypoiodite on Hindered Ketones¹ |date=1935 |last1=Johnson |first1=Robert |last2=Fuson |first2=Reynold C. |journal=Journal of the American Chemical Society |volume=57 |issue=5 |pages=919–920 |bibcode=1935JAChS..57..919J }}

Ammonium hypoiodites can be formed by oxidation of the analogous iodide salts. These and also sodium hypoiodite are useful as oxidizing agents for a various types of organic compounds and also for a reaction analogous to the haloform reaction.

Hypoiodite is one of the active oxidizing agents generated by lactoperoxidase as part of the mammalian innate immune system.{{cite journal |doi= 10.1002/pro.4230 |title= Structural evidence of the oxidation of iodide ion into hyper-reactive hypoiodite ion by mammalian heme lactoperoxidase |date= 2022 |last1= Singh |first1= Prashant K. |last2= Ahmad |first2= Nayeem |last3= Yamini |first3= Shavait |last4= Singh |first4= Rashmi P. |last5= Singh |first5= Amit K. |last6= Sharma |first6= Pradeep |last7= Smith |first7= Michael L. |last8= Sharma |first8= Sujata |last9= Singh |first9= Tej P. |journal= Protein Science |volume= 31 |issue= 2 |pages= 384–395 |pmid= 34761444 |pmc= 8819834 }}{{cite journal | doi = 10.1021/bi026326x | title = Reaction of Lactoperoxidase Compound I with Halides and Thiocyanate | date = 2002 | last1 = Furtmüller | first1 = Paul Georg | last2 = Jantschko | first2 = Walter | last3 = Regelsberger | first3 = Günther | last4 = Jakopitsch | first4 = Christa | last5 = Arnhold | first5 = Jürgen | last6 = Obinger | first6 = Christian | journal = Biochemistry | volume = 41 | issue = 39 | pages = 11895–11900 | pmid = 12269834 }}