Diiodine tetroxide
Chemical compound
From Wikipedia, the free encyclopedia
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.
| Names | |
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| IUPAC name
iodosyl iodate | |
| Identifiers | |
3D model (JSmol) |
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PubChem CID |
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| 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).
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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 → 3I2O4 + 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 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°). The structure is a polymeric zigzag chain of I–O–I-O–... alternating as IVO2 and IIII.[2][3]
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]