Hydrogen polyoxide

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Chemical structure of water, the simplest hydrogen polyoxide

Hydrogen polyoxides (also known as oxidanes, oxohydrogens, or oxyhydrogens) are chemical compounds that consist only of hydrogen and oxygen atoms, are bonded exclusively by single bonds (i.e., they are saturated), and are acyclic (have molecular structures containing no cycles or loops). They can, therefore, be classed as hydrogen chalcogenides.

The simplest possible stable hydrogen polyoxide (the parent molecule) is

single-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 a homologous series with chemical formula H
2O
n in which the members differ by a constant relative molecular 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).

An oxidanyl group is a

hydroxy (oxidyl) and hydroperoxy
(dioxidanyl) groups.

Specific examples

HOn

Several molecules are known where one end of the polyoxide chain is

protonated and the other is an unprotonated radical
:

H2On

Neutral dihydrogen polyoxides containing up to five oxygen atoms have been produced experimentally.

  • Water (H2O) is the most common hydrogen polyoxide, occurring widely on Earth's surface.
  • Hydrogen peroxide (H2O2) is a common disinfectant and readily decomposes to form water and oxygen.
  • Trioxidane (H2O3) is rare and readily decomposes into water and singlet oxygen.
  • peroxy radicals at low temperature.[1]
  • Pentaoxidane (H2O5) is a byproduct of trioxidane production[2] and has also been synthesized by reaction among peroxy radicals at low temperature.[1]

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]

H3On

Ionization

All the hydrogen polyoxides are known or expected to autoionise when in liquid form, with the acidic hydrogen being solvated by other of the neutral polyoxide molecules.

H2On ⇌ H+ + HO–
n
2 H2On ⇌ H
3O+
n + HO–
n

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:

See also

References

  1. ^
    doi:10.1002/ejic.201100767
    .
  2. PMID 12438699
    .
  3. doi:10.1002/qua.22695
    .
  4. arXiv:1908.05821 [physics.comp-ph
    ].
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