Iodine pentoxide

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Iodine pentoxide is the chemical compound with the formula I₂O₅. This iodine oxide is the anhydride of iodic acid. It is produced by dehydrating iodic acid at 200 °C in a stream of dry air:

2HIO₃ → I₂O₅ + H₂O

Structure

I₂O₅ is bent with an I-O-I angle of 139.2°, but the molecule has no mirror plane so its symmetry is not C_2v. 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:

5CO + I₂O₅ → I₂ + 5CO₂

This reaction can be used to analyse 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.