Hydrogen polyoxides (also known as oxidanes, oxohydrogens, or oxyhydrogens) are

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

s that consist only of

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

atoms, are bonded exclusively by single bonds (i.e., they are

saturated Saturation, saturated, unsaturation or unsaturated may refer to: Chemistry * Saturation, a property of organic compounds referring to carbon-carbon bonds ** Saturated and unsaturated compounds **Degree of unsaturation ** Saturated fat or fatty ac ...

), and are acyclic (have molecular structures containing no cycles or loops). They can, therefore, be classed as

hydrogen chalcogenide Hydrogen chalcogenides (also chalcogen hydrides or hydrogen chalcides) are binary compounds of hydrogen with chalcogen atoms (elements of group 16: oxygen, sulfur, selenium, tellurium, and polonium). Water, the first chemical compound in this serie ...

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

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

, H₂O. The general structure of the class of molecules is some number of oxygen atoms

single-bond In chemistry, a single bond is a chemical bond between two atoms involving two valence electrons. That is, the atoms share one pair of electrons where the bond forms. Therefore, a single bond is a type of covalent bond. When shared, each of ...

ed 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 in which the members differ by a constant relative

molecular mass The molecular mass (''m'') is the mass of a given molecule: it is measured in daltons (Da or u). Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element. The related quanti ...

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

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the re ...

or side-chain analog of hydrogen polyoxide that is attached to some structure other than just a hydrogen atom. Examples include the hydroxy (oxidyl) and hydroperoxy (dioxidanyl) groups.

Specific examples

HO_''n''

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

protonated In chemistry, protonation (or hydronation) is the adding of a proton (or hydron, or hydrogen cation), (H+) to an atom, molecule, or ion, forming a conjugate acid. (The complementary process, when a proton is removed from a Brønsted–Lowry acid, ...

and the other is an unprotonated radical: *

Hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydro ...

(HO^•) * Hydroperoxyl (HOO^•), the protonated form of

superoxide In chemistry, a superoxide is a compound that contains the superoxide ion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen ion superoxide is particularly important as the product of t ...

H₂O_''n''

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

Water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

(H₂O) is the most common hydrogen polyoxide, occurring widely on Earth's surface. *

Hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

(H₂O₂) is a common disinfectant and readily decomposes to form water and oxygen. *

Trioxidane Trioxidane (systematically named μ-trioxidanediidodihydrogen), also called dihydrogen trioxide, is an inorganic compound with the chemical formula (can be written as or ). It is one of the unstable hydrogen polyoxides. In aqueous solutions, ...

(H₂O₃) is rare and readily decomposes into water and singlet oxygen. * Tetraoxidane (H₂O₄) has been synthesized by reaction among peroxy radicals at low temperature. * Pentaoxidane (H₂O₅) is a byproduct of trioxidane production and has also been synthesized by reaction among peroxy radicals at low temperature. 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.

H₃O_''n''

* (H₃O), which has been studied theoretically and is expected to be stable at pressures over a few hundred gigapascals.

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. :H₂O_''n'' H⁺ + :2 H₂O_''n'' + Specific ions include: *

Hydroxide Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. I ...

(HO^–) *

Hydronium In chemistry, hydronium (hydroxonium in traditional British English) is the common name for the aqueous cation , the type of oxonium ion produced by protonation of water. It is often viewed as the positive ion present when an Arrhenius acid i ...

(H₃O⁺)

References

{{Hydrides by group Polyoxides

Specific examples

HO''n''

H2O''n''

H3O''n''

Ionization

See also

References

HO_''n''

H₂O_''n''

H₃O_''n''