Iodine pentoxide

{{Chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 450595852 | ImageFile1 = Iodine-pentoxide-3D-balls.png | ImageSize1 = 120px | ImageFile2 = Iodine-pentoxide-3D-vdW.png | ImageSize2 = 120px | IUPACName = Iodine pentoxide | OtherNames = Iodine(V) oxide<br>Iodic anhydride | Section1 = {{Chembox Identifiers | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 140179 | InChI = 1/I2O5/c3-1(4)7-2(5)6 | InChIKey = BIZCJSDBWZTASZ-UHFFFAOYAR | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/I2O5/c3-1(4)7-2(5)6 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = BIZCJSDBWZTASZ-UHFFFAOYSA-N | CASNo_Ref = {{cascite|correct|??}} | CASNo = 12029-98-0 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = UPU35C0Q0N | PubChem = 159402 | ChEBI_Ref = {{ebicite|correct|EBI}} | ChEBI = 29914 | SMILES = O=I(=O)OI(=O)=O }} | Section2 = {{Chembox Properties | Formula = {{Chem|I|2|O|5}} | MolarMass = 333.81 g/mol | Appearance = white crystalline solid<ref name=G&E>{{Greenwood&Earnshaw | pages = 851–852 }}</ref> <br> hygroscopic | Density = 4.980 g/cm³<ref name=G&E/> | MeltingPtC = 300 | MeltingPt_notes = (decomposes) | MeltingPt_ref = <ref>{{cite book | author = Patnaik, P. | title = Handbook of Inorganic Chemicals | publisher = McGraw-Hill | year = 2002 | isbn = 0-07-049439-8 }}</ref> | Solubility = | SolubleOther = soluble in water and nitric acid; <br> insoluble in ethanol, ether and CS₂ | MagSus = &minus;79.4·10⁻⁶ cm³/mol }} | Section3 = {{!}} Section4 = {{Chembox Thermochemistry | Thermochemistry_ref = | HeatCapacity = | Entropy = | DeltaHform = −173.0 kJ/mol | DeltaGfree = | DeltaHcombust = | DeltaHfus = | DeltaHvap = | DeltaHsublim = | HHV = | LHV = }} | Section4 = {{Chembox Hazards | MainHazards = oxidizer | FlashPt = | AutoignitionPt = | NFPA-H = 3 | NFPA-F = 0 | NFPA-R = 0 | NFPA-S = OX }} | Section8 = {{Chembox Related | OtherAnions = iodine pentafluoride }} }} alt=Iodine pentoxide|thumb|Fresh iodine pentoxide '''Iodine pentoxide''' is the chemical compound with the formula I₂O₅. This iodine oxide is the anhydride of iodic acid, and one of the few iodine oxides that is stable. It is produced by dehydrating iodic acid at 200&nbsp;°C in a stream of dry air:<ref name=G&E/>

:2HIO₃ → I₂O₅ + H₂O

This dehydration proceeds through the hydrogen bonded adduct {{chem2|I2O5*HIO3}} (HI₃O₈), which is present in commercial "HIO₃."<ref>{{cite journal |last1=Fischer |first1=Andreas |title=Redetermination of HI₃O₈, an adduct of formula HIO₃·I₂O₅ |journal=Acta Crystallographica Section E |date=15 December 2005 |volume=61 |issue=12 |pages=i278–i279 |doi=10.1107/S1600536805037037}}</ref>

:{{chem2|3 HIO3 -> HI3O8 + H2O}}<ref>{{cite journal |last1=Smith |first1=Dylan K. |last2=McCollum |first2=Jena |last3=Pantoya |first3=Michelle L. |title=Effect of environment on iodine oxidation state and reactivity with aluminum |journal=Physical Chemistry Chemical Physics |date=2016 |volume=18 |issue=16 |pages=11243–11250 |doi=10.1039/C5CP06998J}}</ref>

== Structure == I₂O₅ is bent with an I–O–I angle of 139.2°, but the molecule has no mirror plane so its symmetry is C₂ rather than C_2v. The terminal I–O distances are around 1.80&nbsp;Å and the bridging I–O distances are around 1.95&nbsp;Å.<ref>{{cite journal |author1=Selte, K. |author2=Kjekshus, A. | year = 1970 | title = Iodine Oxides: Part III. The Crystal Structure of I₂O₅ | journal = Acta Chemica Scandinavica | volume = 24 | issue = 6 | pages = 1912–1924 | doi = 10.3891/acta.chem.scand.24-1912 | url = http://actachemscand.org/pdf/acta_vol_24_p1912-1924.pdf | doi-access = free }}</ref>

== Reactions == Iodine pentoxide easily oxidises carbon monoxide to carbon dioxide at room temperature:

:5&nbsp;CO + I₂O₅ → I₂ + 5&nbsp;CO₂

This reaction can be used to analyze the concentration of CO in a gaseous sample.

I₂O₅ forms iodyl salts, [IO₂⁺], with SO₃ and S₂O₆F₂, but iodosyl salts, [IO⁺], with concentrated sulfuric acid.{{dubious|date=February 2026}}

Iodine pentoxide decomposes to iodine (vapor) and oxygen when heated to about 350&nbsp;°C.<ref>G. Baxter and G. Tilley, "A Revision of the Atomic Weights of Iodine and Silver," ''The Chemical News and Journal of Industrial Science; Volumes 99-100'', Royal Society Anniversary Meeting, December 3, 1909, p. 276. ([https://books.google.com/books?id=Rco_AQAAIAAJ&dq=decomposition+of+iodine+pentoxide&pg=PA323-IA375 Google Books])</ref>

==References== {{reflist}}

{{Iodine compounds}} {{Iodides}}{{oxygen compounds}} {{DEFAULTSORT:Iodine Pentoxide}} Category:Iodine(V) compounds Category:Iodine oxides Category:Acidic oxides Category:Oxidizing agents