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 °C in a stream of dry air:
2HIO3 → I2O5 + H2O
This dehydration proceeds through the hydrogen bonded adduct (HI3O8), which is present in commercial "HIO3."
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 C2v. The terminal I–O distances are around 1.80 Å and the bridging I–O distances are around 1.95 Å.
Reactions Iodine pentoxide easily oxidises carbon monoxide to carbon dioxide at room temperature:
5 CO + I2O5 → I2 + 5 CO2
This reaction can be used to analyze the concentration of CO in a gaseous sample.
I2O5 forms iodyl salts, containing [IO2+], when reacted with SO3 and S2O6F2. When heated with concentrated sulfuric acid, it forms iodosyl salts, containing [IO+].https://www.russchemrev.org/RCR282pdf
Iodine pentoxide decomposes to iodine (vapor) and oxygen when heated to about 350 °C.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. (Google Books)
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