Tetraoxidane

Tetraoxidane is an inorganic compound of hydrogen and oxygen with the chemical formula. This is one of the unstable hydrogen polyoxides.

Synthesis
The compound is prepared by a chemical reaction between hydroperoxyl radicals (HO2•) at low temperatures:
 * $$\mathrm{2HO_2^\bullet \xrightarrow{} H_2O_4}$$

Physical properties
This is the fourth member of the polyoxidanes. The first three are water [(mon)oxidane], hydrogen peroxide (dioxidane), and trioxidane. Tetroxidane is more unstable than the previous compounds. The term "tetraoxidane" extends beyond the parent compound to several daughter compounds of the general formula, where R can be hydrogen, halogen atoms, or various inorganic and organic monovalent radicals. The two Rs together can be replaced by a divalent radical, so heterocyclic tetroxidanes also exist.

Ionization
Tetroxidane autoionizes when in liquid form:
 * $$\mathrm{H_2O_4 \rightleftarrows H^+ + HO_4^-}$$
 * $$\mathrm{2H_2O_4 \rightleftarrows H_3O_4^+ + HO_4^-}$$