Superoxide

Hyper oxides or superoxides are chemical compounds derived from the oxygen dioxide (1 -) containing anion ( O2 - ). The oxygen has an oxidation number in these compounds - ½.

Connections with the O22 - anion, such as H2O2 and BaO2, are peroxides, no Hyperoxide.

Name

In the German literature superoxide is often used as a name. Although " superoxide " is mentioned in the biochemical nomenclature, this is not recommended in the German and instead use the systematic name Dioxide (1 - ) is recommended, since the prefix "super" in every language has the same meaning. In English, " superoxide " is accepted by IUPAC as an alternative name for the systematic name. " Hyperoxide " is, however, considered by IUPAC as obsolete.

Properties

The Hyper oxides of alkali and alkaline earth metals are yellow to orange, crystalline, paramagnetic solid. When heated without oxygen they decompose to form the corresponding peroxides and oxygen evolution. Hyperoxide disproportionation in the presence of water with evolution of oxygen and formation of hydrogen peroxide and hydroxides:

Education

Hyper oxides generated during the combustion of the alkali metals potassium, rubidium and cesium, in the presence of oxygen. While sodium burns mainly to the peroxide. Lithium - even with a large excess of oxygen - mainly the oxide. The reason for the different behavior lies in the increase of the ionic radius with increasing period of alkali metal, the increase in softness of the cations and the gain in lattice energy: while the small, hard lithium cation which is also small and hard oxide anion preferred binding partner in the ion crystal occurs from potassium, rubidium or cesium, but especially when the large, much softer superoxide anion in its place.

Biochemistry

Hyperoxide also occur during normal metabolic processes in the course of the reduction of molecular oxygen, for example in the respiratory chain and can possibly destroy cell structures irreversibly due to their high reactivity. They are therefore assigned to the reactive oxygen species ( ROS RSS or English ). For quick removal of such free radicals, the enzyme superoxide dismutase is responsible. The reaction is similar to the decomposition in aqueous solution via a disproportionation of Hyperoxids in oxygen and peroxide. The latter is free of hydrogen peroxide, which is further detoxified by catalase to water and oxygen. But that hydrogen peroxide can also peroxidases (eg degradation of lignin or aromatic ) and haloperoxidases find use in the organism.

Recent studies write to an important signaling function for example in the brain in signal transmission, synaptic plasticity and memory formation, such as the RSS superoxide and hydrogen peroxide in addition to generation of oxidative stress. They work there also heavily vasodilator ( vasodilators ) and seem therefore important for the increase of cerebral blood flow and cerebrovascular tone to be.