Diiodine tetroxide

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Diiodine tetroxide[1]
Names
IUPAC name
iodosyl iodate
Identifiers
3D model (JSmol)
  • InChI=1S/I2O4/c3-1-6-2(4)5
    Key: XHTWXUOEQMOFEJ-UHFFFAOYSA-N
  • O=IOI(=O)=O
Properties
I2O4
Molar mass 317.805 g·mol−1
Density 2.57
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Diiodine tetraoxide, I2O4, is a chemical compound of oxygen and iodine. It belongs to the class of iodine oxides, and is a mixed oxide, consisting of iodine(III) and iodine(V) oxidation states.

Synthesis

The oxide is formed by the reaction of hot concentrated sulfuric acid on iodic acid for several days.[2]

3HIO3 → I2O4 + HIO4 + H2O

It is formed from diiodine pentoxide and iodine in concentrated sulfuric acid or iodosyl sulfate (IO)2SO4 added to water:[3]

4(IO)2SO4 + 4H2O → I2O4 + I2 + 4H2SO4

Alternatively, excess of concentrated nitric acid oxidizes dry iodine to this salt.[4]

Physical properties

Diiodine tetraoxide is a yellow, granular powder. At temperatures above 85 °C it decomposes to diiodine pentoxide and iodine:[2]

5I2O4 → 4I2O5 + I2

This process is even faster at 135 °C. It dissolves in hot water to form iodate and iodide.[2] Structurally, the compound is an iodyl iodite O2I-OIO (iodine(V,III) oxide)[2] with bent IVO2 units (I–O distances 1.80 and 1.85 Å; ∠OIO angle 97°) and bent IIIIO2 units (IO distances 1.93 Å, OIO angle 95.8°). Both units are linked via I—O—I bridges to form polymeric zigzag chains (I2O4)x.[2]

Diiodine tetraoxide has a monoclinic crystal structure with the space group P21/c (space group number 14). Unit cell dimensions are a = 8.483 b = 6.696 c = 8.333 Å and β = 124.69°. Unit cell volume = 389.15 Å3. Z = 4. Density is 2.57 Mg/m3[3][5]

Reactions

Diiodine tetroxide oxidises hydrochloric acid:[6]

I2O4 + 8H+ + 8Cl− → 2ICl + 4H2O + 3Cl2

It decomposes[vague] in water.[4][7]

References

  1. ^ William M. Haynes, ed. (2014). CRC Handbook of Chemistry and Physics. CRC Press. p. S.4-67. ISBN 978-1482208689.
  2. ^ a b c d e Holleman-Wiberg inorganic chemistry. San Diego, Calif. London: Academic. 2001. pp. 465–466. ISBN 0123526515.
  3. ^ a b Fjellvåg, Helmer; Kjekshus, Arne; Persson, Ingmar; Figgis, Brian N.; Liaaen-Jensen, Synnøve; Balzarini, Jan; Fransson, Bengt; Ragnarsson, Ulf; Francis, George W. (1994). "The Crystal Structure of I2O4 and its Relations to Other Iodine--Oxygen-Containing Compounds". Acta Chemica Scandinavica. 48: 815–822. doi:10.3891/acta.chem.scand.48-0815.
  4. ^ a b Holmyard, E. J. (1931). Inorganic Chemistry. Edward Arnold & Co. p. 521. ISBN 978-5-87636-953-6. Retrieved 10 May 2023.
  5. ^ Wu, Zhongqing; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya (28 May 2011). "First-principles calculations of the structural and dynamic properties, and the equation of state of crystalline iodine oxides I2O4, I2O5, and I2O6". The Journal of Chemical Physics. 134 (20). doi:10.1063/1.3590278. PMID 21639450.
  6. ^ Advances in Inorganic Chemistry and Radiochemistry. Academic Press. 1 January 1963. p. 77-78. ISBN 978-0-08-057854-5.
  7. ^ Perry, Dale L. (19 April 2016). Handbook of Inorganic Compounds. CRC Press. p. 210. ISBN 978-1-4398-1462-8. Retrieved 10 May 2023.
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