Hypoiodous acid

Hypoiodous acid
Hydrogen, H Oxygen, O Iodine, I
Names
	IUPAC name Hypoiodous acid
Identifiers
CAS Number	14332-21-9 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:29231 ;
ChemSpider	109942 ;
PubChem CID	123340;
UNII	2PYC923C5W ;
CompTox Dashboard (EPA)	DTXSID8042050 ;
	InChI InChI=1S/HIO/c1-2/h2H Key: GEOVEUCEIQCBKH-UHFFFAOYSA-N ;
	SMILES IO;
Properties
Chemical formula	HOI
Molar mass	143.911 g·mol−1
Acidity (pKa)	10.5 (in water, estimate)
Conjugate base	Hypoiodite
Related compounds
Related compounds	Hypofluorous acid; Hypochlorous acid; Hypobromous acid;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Hypoiodous acid is an inorganic compound with the chemical formula H I O. It forms when an aqueous solution of iodine is treated with mercuric or silver salts. It rapidly decomposes by disproportionation:^[2]

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 (IO⁻). Salts of this anion can be prepared by treating iodine with alkali hydroxides. They rapidly disproportionate to form iodides and iodates,^[2] but an iodine–hydroxide mixture can be used an in situ preparation of hypoiodite for other reactions.^[3]

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.^[3]

Hypoiodite is one of the active oxidizing agents generated by lactoperoxidase as part of the mammalian innate immune system.^[4]^[5]

Other oxyacids

Hypoiodous acid is part of a series of oxyacids in which iodine can assume oxidation states of −1, +1, +3, +5, or +7. A number of neutral iodine oxides are also known.

Iodine oxidation state	−1	+1	+3	+5	+7
Name	Hydrogen iodide	Hypoiodous acid	Iodous acid	Iodic acid	Periodic acid
Formula	HI	HIO	HIO₂	HIO₃	HIO₄ or H₅IO₆

References

^ Perrin, D. D., ed. (1982) [1969]. Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2nd ed.). Oxford: Pergamon (published 1984). Entry 119. ISBN 0-08-029214-3. LCCN 82-16524.
^ ^a ^b Holleman, A.F. (2001). Wiberg, Nils (ed.). Inorganic chemistry (1st English ed.). San Diego, Calif. : Berlin: Academic Press, W. de Gruyter. ISBN 0-12-352651-5.
^ ^a ^b Johnson, Robert; Fuson, Reynold C. (1935). "The Haloform Reaction. XVI. The Action of Hypoiodite on Hindered Ketones¹". Journal of the American Chemical Society. 57 (5): 919–920. Bibcode:1935JAChS..57..919J. doi:10.1021/ja01308a043.
^ Singh, Prashant K.; Ahmad, Nayeem; Yamini, Shavait; Singh, Rashmi P.; Singh, Amit K.; Sharma, Pradeep; Smith, Michael L.; Sharma, Sujata; Singh, Tej P. (2022). "Structural evidence of the oxidation of iodide ion into hyper-reactive hypoiodite ion by mammalian heme lactoperoxidase". Protein Science. 31 (2): 384–395. doi:10.1002/pro.4230. PMC 8819834. PMID 34761444.
^ Furtmüller, Paul Georg; Jantschko, Walter; Regelsberger, Günther; Jakopitsch, Christa; Arnhold, Jürgen; Obinger, Christian (2002). "Reaction of Lactoperoxidase Compound I with Halides and Thiocyanate". Biochemistry. 41 (39): 11895–11900. doi:10.1021/bi026326x. PMID 12269834.

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[P82db-1] Perrin, D. D., ed. (1982) [1969]. Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2nd ed.). Oxford: Pergamon (published 1984). Entry 119. ISBN 0-08-029214-3. LCCN 82-16524.

[Wiberg&Holleman-2] Holleman, A.F. (2001). Wiberg, Nils (ed.). Inorganic chemistry (1st English ed.). San Diego, Calif. : Berlin: Academic Press, W. de Gruyter. ISBN 0-12-352651-5.

[haloform-3] Johnson, Robert; Fuson, Reynold C. (1935). "The Haloform Reaction. XVI. The Action of Hypoiodite on Hindered Ketones¹". Journal of the American Chemical Society. 57 (5): 919–920. Bibcode:1935JAChS..57..919J. doi:10.1021/ja01308a043.

[4] Singh, Prashant K.; Ahmad, Nayeem; Yamini, Shavait; Singh, Rashmi P.; Singh, Amit K.; Sharma, Pradeep; Smith, Michael L.; Sharma, Sujata; Singh, Tej P. (2022). "Structural evidence of the oxidation of iodide ion into hyper-reactive hypoiodite ion by mammalian heme lactoperoxidase". Protein Science. 31 (2): 384–395. doi:10.1002/pro.4230. PMC 8819834. PMID 34761444.

[5] Furtmüller, Paul Georg; Jantschko, Walter; Regelsberger, Günther; Jakopitsch, Christa; Arnhold, Jürgen; Obinger, Christian (2002). "Reaction of Lactoperoxidase Compound I with Halides and Thiocyanate". Biochemistry. 41 (39): 11895–11900. doi:10.1021/bi026326x. PMID 12269834.

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[2]

[3]

[4]

[5]

Hypoiodous acid

Other oxyacids

References

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