Superoksid

Superoksid, often referred to in chemistry as superoxide, denotes species derived from the one-electron reduction of molecular oxygen. It most commonly exists as the superoxide anion O2− or as the superoxide radical O2•−, and it is a reactive oxygen species involved in a range of chemical and biological processes.

Chemistry and formation

Superoxides form when oxygen gains a single electron, producing a negatively charged O2− unit or a radical species depending on the environment. In aqueous solutions, the speciation between O2− and HO2• (hydroperoxyl radical) depends on pH, with HO2• being more prominent at lower pH. Superoxide is relatively unstable in many conditions and participates in rapid redox reactions, including dismutation, where two superoxide molecules convert to hydrogen peroxide and oxygen.

Biological role and health relevance

In living organisms, superoxide is produced by mitochondrial respiration, NADPH oxidases, and other enzymes. It serves as a signaling molecule at controlled levels but can contribute to oxidative stress when produced in excess. Superoxide is rapidly converted by superoxide dismutase to hydrogen peroxide, which can be further processed by catalase or peroxidases. Interactions with nitric oxide and metal ions can generate other reactive species, influencing inflammation, aging, and cellular damage.

Industrial and practical context

Alkali metal superoxides (for example, potassium superoxide) are known for releasing oxygen upon contact with water or acids, a property exploited in some chemical oxygen sources for life-support systems and space suits. They are strong oxidizers and must be handled with care to avoid hazardous reactions with moisture and flammable materials.

See also: Superoxide dismutase, Reactive oxygen species, Oxidative stress.