Iodine oxide
{{Short description|Class of chemical compounds}}
Image:Iodine-pentoxide-3D-balls.png (I2O5)]]
Iodine oxides are chemical compounds of oxygen and iodine. Iodine has only two stable oxides which are isolatable in bulk, iodine tetroxide and iodine pentoxide, but a number of other oxides are formed in trace quantities or have been hypothesized to exist.
The chemistry of these compounds is complicated with only a few having been well characterized. Many have been detected in the atmosphere and are believed to be particularly important in the marine boundary layer.{{cite journal|last1=Kaltsoyannis|first1=Nikolas|last2=Plane|first2=John M. C.|title=Quantum chemical calculations on a selection of iodine-containing species (IO, OIO, INO3, (IO)2, I2O3, I2O4 and I2O5) of importance in the atmosphere|journal=Physical Chemistry Chemical Physics|date=2008|volume=10|issue=13|pages=1723–33|doi=10.1039/B715687C|pmid=18350176|bibcode=2008PCCP...10.1723K}}
Molecular compounds
Diiodine monoxide has largely been the subject of theoretical study,{{cite journal|last1=Novak|first1=Igor|title=Theoretical study of I2O|journal=Heteroatom Chemistry|date=1998|volume=9|issue=4|pages=383–385|doi=10.1002/(SICI)1098-1071(1998)9:4<383::AID-HC6>3.0.CO;2-9}} but there is some evidence that it may be prepared in a similar manner to dichlorine monoxide, via a reaction between HgO and I2.{{cite journal|last1=Forbes|first1=Craig P.|last2=Goosen|first2=André|last3=Laue|first3=Hugh A. H.|title=Hypoiodite reaction: kinetic study of the reaction of 1,1-diphenyl-ethylene with mercury(II) oxide iodine|journal=Journal of the Chemical Society, Perkin Transactions 1|date=1974|pages=2350–2353|doi=10.1039/P19740002350}} The compound appears to be highly unstable but can react with alkenes to give halogenated products.{{cite journal|last1=Cambie|first1=Richard C.|last2=Hayward|first2=Rodney C.|last3=Lindsay|first3=Barry G.|last4=Phan|first4=Alice I. T.|last5=Rutledge|first5=Peter S.|last6=Woodgate|first6=Paul D.|title=Reactions of iodine oxide with alkenes|journal=Journal of the Chemical Society, Perkin Transactions 1|date=1976|issue=18|pages=1961|doi=10.1039/P19760001961}}
Radical iodine oxide (IO), iodine dioxide (IO2), collectively referred to as I{{mvar|x}}O{{mvar|y}} and iodine tetroxide ((I2O4) all possess significant and interconnected atmospheric chemistry. They are formed, in very small quantities, in the marine boundary layer by the photooxidation of diiodomethane, which is produced by macroalga such as seaweed or through the oxidation of molecular iodine, produced by the reaction of gaseous ozone and iodide present at the seasurface.{{cite journal|last1=Hoffmann|first1=Thorsten|last2=O'Dowd|first2=Colin D.|last3=Seinfeld|first3=John H.|title=Iodine oxide homogeneous nucleation: An explanation for coastal new particle production|journal=Geophysical Research Letters|date=15 May 2001|volume=28|issue=10|pages=1949–1952|doi=10.1029/2000GL012399|bibcode=2001GeoRL..28.1949H|url=https://authors.library.caltech.edu/50961/1/grl14261.pdf|doi-access=free}}{{cite journal|last1=Carpenter|first1=Lucy J.|last2=MacDonald|first2=Samantha M.|last3=Shaw|first3=Marvin D.|last4=Kumar|first4=Ravi|last5=Saunders|first5=Russell W.|last6=Parthipan|first6=Rajendran|last7=Wilson|first7=Julie|last8=Plane|first8=John M.C.|title=Atmospheric iodine levels influenced by seasurface emissions of inorganic iodine|journal=Nature Geoscience|date=13 January 2013|volume=6|issue=2|pages=108–111|doi=10.1038/ngeo1687|bibcode=2013NatGe...6..108C|url=http://eprints.whiterose.ac.uk/76461/7/Nge01687%20-%20pre-publication%20version_with_coversheet.pdf}} Despite the small quantities produced (typically below ppt) they are thought to be powerful ozone depletion agents.{{cite journal|last1=Saiz-Lopez|first1=A.|last2=Fernandez|first2=R. P.|last3=Ordóñez|first3=C.|last4=Kinnison|first4=D. E.|last5=Gómez Martín|first5=J. C.|last6=Lamarque|first6=J.-F.|last7=Tilmes|first7=S.|title=Iodine chemistry in the troposphere and its effect on ozone|journal=Atmospheric Chemistry and Physics|date=10 December 2014|volume=14|issue=23|pages=13119–13143|doi=10.5194/acp-14-13119-2014|bibcode=2014ACP....1413119S|doi-access=free|hdl=11336/100317|hdl-access=free}}{{cite journal|last1=Cox|first1=R. A.|last2=Bloss|first2=W. J.|last3=Jones|first3=R. L.|last4=Rowley|first4=D. M.|title=OIO and the atmospheric cycle of iodine|journal=Geophysical Research Letters|date=1 July 1999|volume=26|issue=13|pages=1857–1860|doi=10.1029/1999GL900439|bibcode=1999GeoRL..26.1857C|s2cid=128402214 |url=http://pure-oai.bham.ac.uk/ws/files/11849889/Cox_OIO_and_the_Atmospheric_Cycle_of_Iodine_GRL_1999.pdf}}
Diiodine pentoxide (I2O5) is the anhydride of iodic acid and the only stable anhydride of an iodine oxoacid.
Tetraiodine nonoxide (I4O9) has been prepared by the gas-phase reaction of I2 with O3 but has not been extensively studied.{{cite journal|last1=Sunder|first1=S.|last2=Wren|first2=J. C.|last3=Vikis|first3=A. C.|title=Raman spectra of I4O9 formed by the reaction of iodine with ozone|journal=Journal of Raman Spectroscopy|date=December 1985|volume=16|issue=6|pages=424–426|doi=10.1002/jrs.1250160611|bibcode=1985JRSp...16..424S}}
Iodate anions
Iodine oxides also form negatively charged anions, which (associated with complementary cations) are components of acids or salts. These include the iodates and periodates.
Their conjugate acids are:
| class="wikitable" |
| Iodine oxidation state
| −1 | +1 | +3 | +5 | +7 |
|---|
| Name |
| Formula
| HI | HIO | HIO2 | HIO3 | HIO4 or H5IO6 |
{{*}}The −1 oxidation state, hydrogen iodide, is not an oxide, but it is included in this table for completeness.
The periodates include two variants: metaperiodate {{chem|IO|4|−}} and orthoperiodate {{chem|IO|6|5−}}.
See also
References
{{Reflist}}
{{Iodine compounds}}
{{Iodides}}{{Use dmy dates|date=March 2018}}