Hydrogen polyoxides (also known asoxidanes,oxohydrogens, oroxyhydrogens) arechemical compounds that consist only ofhydrogen andoxygen atoms, are bonded exclusively bysingle bonds (i.e., they aresaturated), and areacyclic (have molecular structures containing no cycles or loops). They can therefore be classed ashydrogen chalcogenides.
The simplest possible stable hydrogen polyoxide (the parent molecule) iswater, H2O. The general structure of the class of molecules is some number of oxygen atomssingle-bonded to each other in a chain. The oxygen atom at each end of this oxygen skeleton is attached to a hydrogen atom. Thus, these compounds form ahomologous series with chemical formulaH
2O
n in which the members differ by a constant relativemolecular mass of 16 (the mass of each additional oxygen atom). The number of oxygen atoms is used to define the size of the hydrogen polyoxide (e.g., hydrogen pentoxide contains a five-oxygen backbone).
Anoxidanyl group is afunctional group or side-chain analog of hydrogen polyoxide that is attached to some structure other than just a hydrogen atom. Examples include thehydroxy (oxidyl) andhydroperoxy (dioxidanyl) groups.
Several molecules are known where one end of the polyoxide chain isprotonated and the other is an unprotonatedradical:
Neutral dihydrogen polyoxides containing up to five oxygen atoms have been produced experimentally.
Hydrogen polyoxides containing up to 10 oxygen atoms have been studied theoretically, but those containing more than five oxygens are expected to be extremely unstable.[3]
All the hydrogen polyoxides are known or expected toautoionise when in liquid form, with the acidic hydrogen beingsolvated by other of the neutral polyoxide molecules.
The ions can also be formed by protonation or deprotonation of various neutral hydrogen polyoxide by suitably strong other acids or bases.Specific ions include: