Iodate
{{Short description|Polyatomic anion (IO3) with charge -1}}
{{Chembox
|ImageFile=File:iodate anion.svg
|ImageCaption=The iodate anion, {{chem2|IO3-}}
|ImageFile1=iodate-3D-vdW.png
|ImageCaption1=Space-filling model of the iodate anion
|Section1={{Chembox Identifiers
| CASNo = 15454-31-6
| ChEBI = 29226
| ChEBI1_Comment=(class of salts)
| ChEBI1 = 24856
| ChemSpiderID = 76615
| Gmelin=1676
| PubChem = 84927
| UNII = 877S7T6EXV
| StdInChI=1S/HIO3/c2-1(3)4/h(H,2,3,4)/p-1
| StdInChIKey = ICIWUVCWSCSTAQ-UHFFFAOYSA-M
| SMILES = [O-]I(=O)=O
}}
|Section2={{Chembox Properties
| I=1|O=3|Formula_Charge=−
}}
|Section8={{Chembox Related
| OtherCompounds=Periodate, Fluoroiodate, Bromate, Chlorate
}}
}}
An iodate is the polyatomic anion with the formula {{chem2|IO3-}}. It is the most common form of iodine in nature, as it comprises the major iodine-containing ores.{{Ullmann|last = Lyday|first = Phyllis A.|year = 2005|title = Iodine and Iodine Compounds|pages = 382–390|doi = 10.1002/14356007.a14_381}} Iodate salts are often colorless. They are the salts of iodic acid.
Structure
Iodate is pyramidal in structure. The O–I–O angles range from 97° to 105°, somewhat smaller than the O–Cl–O angles in chlorate.{{Greenwood&Earnshaw2nd}}
Reactions
=Redox=
Iodate is one of several oxyanions of iodine, and has an oxidation number of +5. It participates in several redox reactions, such as the iodine clock reaction. Iodate shows no tendency to disproportionate to periodate and iodide, in contrast to the situation for chlorate.
:{{chem2|6HSO3- + 2IO3- -> 2I- + 6HSO4-}}
Iodate oxidizes iodide:
:{{chem2|5I- + IO3- + 3H2SO4 -> 3I2 + 3H2O + 3SO4(2-)}}
Similarly, chlorate oxidizes iodide to iodate:
:{{chem2|I- + ClO3- -> Cl- + IO3-}}
Iodate is also obtained by reducing a periodate with a sulfide. The byproduct of the reaction is a sulfoxide.{{cite journal |last=Qiu |first=Chao |author2=Sheng Han |author3=Xingguo Cheng |author4= Tianhui Ren |year=2005 |url=https://pubs.acs.org/doi/abs/10.1021/ie048833b |title=Distribution of Thioethers in Hydrotreated Transformer Base Oil by Oxidation and ICP-AES Analysis |journal=Industrial & Engineering Chemistry Research |volume=44 |issue=11 |pages=4151–4155 |doi=10.1021/ie048833b |quote=Thioethers can be oxidized to sulfoxides by periodate, and periodate is reduced to iodate}}
=Acid-base=
Iodate is unusual in that it forms a strong hydrogen bond with its parent acid:
:{{chem2| IO3- + HIO3 -> H(IO3)2-}}
The anion {{chem2|H(IO3)2-}} is referred to as biiodate.
Principal compounds
- Calcium iodate, Ca(IO3)2, is the principal ore of iodine. It is also used as a nutritional supplement for cattle.
- Potassium iodate, KIO3, like potassium iodide, has been issued as a prophylaxis against radioiodine absorption in some countries.{{cite web|url=http://www.rpii.ie/Site/Media/Press-Releases/Radioactivity-released-from-Wylfa-nuclear-power-pl.aspx |title=Radiological Protection Institute of Ireland | | Media | Press releases | Radioactivity released from Wylfa nuclear power plant is extremely low and of no health significance |access-date=2013-04-08 |url-status=dead |archive-url=https://web.archive.org/web/20131017221002/http://www.rpii.ie/Site/Media/Press-Releases/Radioactivity-released-from-Wylfa-nuclear-power-pl.aspx |archive-date=2013-10-17 }}{{Cite web |url=http://www.dohc.ie/press/releases/2008/20080403c.html |title=Decision to Discontinue the Future Distribution of Iodine Tablets |access-date=2013-05-22 |archive-url=https://web.archive.org/web/20131018013248/http://www.dohc.ie/press/releases/2008/20080403c.html |archive-date=2013-10-18 |url-status=dead }} It is also one of the iodine compounds used to make iodized salt.{{Cite journal |last1=Arroyave |first1=Guillermo |last2=Pineda |first2=Oscar |last3=Scrimshaw |first3=Nevin S. |date=1956 |orig-date=May 1955 |title=The stability of potassium iodate in crude table salt |journal=Bulletin of the World Health Organization |volume=14 |issue=1 |pages=183–185 |pmid=13329845 |pmc=2538103}}
- Potassium hydrogen iodate (or potassium biiodate), KH(IO3)2, is a double salt of potassium iodate and iodic acid, as well as an acid itself.
- When some oxygen is replaced by fluorine, fluoroiodates are produced.
Natural occurrence
Minerals containing iodate are found in the caliche deposits of Chile. The most important iodate minerals are lautarite and brüggenite, but also copper-bearing iodates such as salesite are known.{{cite web |url=http://www.mindat.org/ |title=Home |website=mindat.org}}
Natural waters contain iodine in the form of iodide and iodate, their ratio being dependent on redox conditions and pH. Iodate is the second most abundant form in water. It is mostly associated with alkaline waters and oxidizing conditions.{{cite web |author1=Sweden |title=Iodine (including PVP-iodine) Product types 1, 3, 4, 22 (EU 528/2012 assessment) |url=https://echa.europa.eu/documents/10162/60b4984a-340e-8aac-075f-2bdd1751d64d |pages=29–30 |date=13 December 2013}}