Peroxyanions

Peroxyanions are a class of chemical species containing the peroxide functional group, which consists of two oxygen atoms bonded together in a chain, with a negative charge or charges distributed across the structure. The most common and simplest peroxyanion is the peroxide ion, O2^2-, which is the dianion of hydrogen peroxide. This ion is characterized by a relatively weak oxygen-oxygen single bond.

Other related species that are sometimes grouped with peroxyanions include the superoxide ion, O2^-, which has a single unpaired electron and a bond order between a single and double bond, and the dioxygenyl ion, O2^+, which has a bond order between a double and triple bond. However, strictly speaking, peroxyanions refer to species with the O2^2- moiety or its derivatives.

The peroxide ion, O2^2-, is a reducing agent and can readily react with oxidizing agents. It is also a relatively strong base. In solution, it can undergo disproportionation reactions to form oxygen and hydroxide ions. Peroxyanions are found in various inorganic peroxides, such as sodium peroxide (Na2O2) and barium peroxide (BaO2), where they are counterbalanced by positive metal ions. These compounds are often used as oxidizing agents or sources of hydrogen peroxide. The chemistry of peroxyanions is important in areas such as bleaching, disinfection, and certain industrial processes.