Hypoiodous acid is an inorganic compound with the chemical formula . It forms when an aqueous solution of iodine is treated with mercuric or silver salts. It rapidly decomposes by disproportionation:[1]
Hypoiodites of alkali and alkaline earth metals can be made in cold dilute solutions if iodine is added to their respective hydroxides.Hypoiodous acid is a weak acid with a pKa of about 11. The conjugate base is hypoiodite . Salts of this anion can be prepared by treating with alkali hydroxides. They rapidly disproportionate to form iodides and iodates.[1]
Hypoiodous acid is part of a series of oxyacids in which iodine can assume oxidation states of −1, +1, +3, +5, or +7. A number of neutral iodine oxides are also known.
| Iodine oxidation state | −1 | +1 | +3 | +5 | +7 | |
|---|---|---|---|---|---|---|
| Name | Hydrogen iodide | Hypoiodous acid | Iodous acid | Iodic acid | Periodic acid | |
| Formula | HI | HIO | HIO2 | HIO3 | HIO4 or H5IO6 |