, organic hydroperoxide, peracid. The peroxide group is marked in . R, R1 and R2 mark hydrocarbon moieties.]] Peroxide is a compound containing an oxygen–oxygen bond. The O−O group is called the peroxide group or peroxo group. In contrast to oxide ions, the oxygen atoms in the peroxide ion have an oxidation state of −1. The most common peroxide is hydrogen peroxide (H2O2), colloquially known as "peroxide." It is marketed as a solution in water at various concentrations. Since hydrogen peroxide is colorless, so are these solutions. It is mainly used as an oxidant and bleaching agent. Concentrated solutions are potentially dangerous when in contact with organic compounds. Aside from hydrogen peroxide, some other major classes of peroxides are these:
- Peroxy acids, the peroxy derivatives of many familiar acids, examples being peroxysulfuric acid and peracetic acid.
- Metal peroxides, examples being barium peroxide (BaO2) and sodium peroxide (Na2O2).
- Organic peroxides, compounds with the linkage C-O-O-C/H. One example is tert-butylhydroperoxide
- Main group peroxides, compounds with the linkage E-O-O-E (E = main group element), one example is potassium peroxydisulfate.