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 a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

and

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

atoms, are bonded exclusively by

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 th ...

s (i.e., they are saturated), 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, polonium, and livermorium). Water, the first chemical compound i ...

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

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

, H₂O. The general structure of the class of molecules is some number of oxygen atoms 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 In organic chemistry, a homologous series is a sequence of compounds with the same functional group and similar chemical properties in which the members of the series differ by the number of repeating units they contain. This can be the length of ...

with chemical formula in which the members differ by a constant relative

molecular mass The molecular mass () is the mass of a given molecule, often expressed in units of daltons (Da). Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element. The derived quan ...

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 any substituent or moiety (chemistry), moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions r ...

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), usually denoted by H+, to an atom, molecule, or ion, forming a conjugate acid. (The complementary process, when a proton is removed from a Br� ...

and the other is an unprotonated

radical Radical (from Latin: ', root) may refer to: Politics and ideology Politics *Classical radicalism, the Radical Movement that began in late 18th century Britain and spread to continental Europe and Latin America in the 19th century *Radical politics ...

: *

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 hydroxy ...

(HO^•) *

Hydroperoxyl The hydroperoxyl radical, also known as the hydrogen superoxide, is the protonated form of superoxide with the chemical formula HO2, also written HOO•. This species plays an important role in the atmosphere and as a reactive oxygen species ...

(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 ...

* Hydrogen ozonide (HOOO^•), the protonated form of

ozonide Ozonide is the polyatomic anion . Cyclic organic compounds formed by the addition of ozone () to an alkene are also called ozonides. Ionic ozonides Inorganic ozonides are dark red salts. The anion has the bent shape of the ozone molecule. In ...

H₂O_''n''

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

Water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

(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 viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

(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 Singlet oxygen, systematically named dioxygen(singlet) and dioxidene, is a gaseous inorganic chemistry, inorganic chemical with the formula O=O (also written as or ), which is in a quantum state where all electrons are Radical (chemistry), spin p ...

. * Tetraoxidane (H₂O₄) has been synthesized by reaction among

peroxy In chemistry, peroxides are a group of compounds with the structure , where the R's represent a radical (a portion of a complete molecule; not necessarily a free radical) and O's are single oxygen atoms. Oxygen atoms are joined to each other and ...

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''

* Trihydrogen oxide (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'' + 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: *

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. It ...

(HO^–) *

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

(H₃O⁺) *

Protonated ozone Protonated ozone is a hydrogen polyoxide having the molecular formula (also written ). It is a cationic structure consisting of an ozone unit with a hydrogen atom attached to one end. This substance is proposed to exist as an intermediate in se ...

(HO₃⁺)

References

{{Hydrides by group Polyoxides

Specific examples

HO''n''

H2O''n''

H3O''n''

Ionization

See also

References

HO_''n''

H₂O_''n''

H₃O_''n''