Iodine oxide


Iodine oxides are chemical compounds of oxygen and iodine. Iodine has at least three stable oxides which are isolable in bulk, diiodine tetroxide, iodine pentoxide, and diiodine hexaoxide, but a number of other oxides are formed in trace quantities or have been hypothesized to exist. The most significant of these is iodine pentoxide, which is distinguished by being the most thermodynamically and kinetically stable of all halogen oxides.
The chemistry of these compounds is complicated, with only a few having been well characterized. Many have been detected in the atmosphere and are believed to be particularly important in the marine boundary layer.

Molecular compounds

Diiodine monoxide has largely been the subject of theoretical study, but there is some evidence that it may be prepared in a similar manner to dichlorine monoxide, via a reaction between HgO and I2. The compound appears to be highly unstable but can react with alkenes to give halogenated products.
Radical iodine oxide and iodine dioxide, collectively referred to as IO, and also iodine tetroxide all possess significant and interconnected atmospheric chemistry. They are formed, in very small quantities, in the marine boundary layer by the photochemical reaction of ozone with diiodomethane, produced by macroalga such as seaweed, or through the oxidation of molecular iodine, produced by the reaction of gaseous ozone and iodide present at the seasurface. Despite the small quantities produced they are thought to be powerful ozone depletion agents.
Diiodine pentoxide is the anhydride of iodic acid and the only stable anhydride of out of all halogen oxoacids. Unlike other halogen oxides, it can be synthesized by thermal dehydration of iodic acid. Iodine pentoxide adopts multiple polymorphs that can be synthesized by varying pressures.
Tetraiodine nonoxide has been prepared by the gas-phase reaction of I2 with O3 but has not been extensively studied.
Diiodine hexaoxide, also known as iodine trioxide or diiodine oxide, is a hygroscopic yellow solid. It has been isolated in bulk and has been studied as a mix with aluminium for destroying chemical and biological agents.
It can be synthesized in hot concentrated sulfuric acid, starting either with pure H5IO6 or a mix of H5IO6 and HIO3 It adopts a polymeric structure consisting of IV and IVII centers.
Diiodine heptoxide has been reported as a yellow solid that slowly decomposes into oxygen at room temperature with rapid decomposition beginning at 60 °C, converting it into I2O6.

Iodate anions

Iodine oxides also form negatively charged anions, which are components of acids or salts. These include the iodates and periodates, which can form multinuclear structures such as 4-.
The conjugate acids of the iodine oxides are:
Iodine oxidation state+1+3+5+7
NameHypoiodous acidIodous acidIodic acidPeriodic acid
FormulaHIOHIO2HIO3HIO4 or H5IO6

The periodates include two main variants: metaperiodate and orthoperiodate.