Peroxide
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In chemistry, peroxides are a group of compounds with the structure R−O−O−R, where R is any element or radical. The O−O group in a peroxide is called the peroxide group, also called peroxy group or peroxo group.
Contents
General
Peroxides are oxidizing agents. Organic peroxides tend to be explosive, but some, like peroxy acids are simply powerful oxidizing agents.
Most peroxides tend to be solid at standard conditions, but hydrogen peroxide and some organic peroxides like MEKP are liquid.
Types
- Inorganic peroxides: peroxides of various elements, usually metallic peroxides (barium peroxide BaO2, zinc peroxide ZnO2), but nonmetallic peroxides also exist (hydrogen peroxide H2O2, peroxydisulfates S2O82-);
- Organic peroxides: organic compounds that contain O-O bonds, most tend to be explosive materials, though a handful are mild oxidizing agents: acetone peroxide, HMTD, ascaridole, benzoyl peroxide;
- Peroxyacids: peroxymonosulfuric acid, peroxydisulfuric acid, peracetic acid;
Availability
Hydrogen peroxide can be bought from pharmacies, swimming pool suppliers, vet shops, at varying concentrations.
Peroxydisulfates can be bought from various electronic shops and online, as PCB etchant.
Ascaridole is one of the few naturally-occurring peroxides, and can be extracted from the Epazote plant, albeit large amounts of the plant is required to obtain a significant amount.
Preparation
Most peroxides, like metal peroxides or organic peroxides can be prepared by adding hydrogen peroxide to the metallic salt, or the organic compound (ketone, carboxylic acid).
Metal peroxides, like those of alkali metals and alkali metal peroxides can be produced by heating their respective metal oxide in oxygen at high temperatures.
Hydrogen peroxide can be prepared through several methods, the most important route being the anthraquinone process, which is not easy to do at home. It can also be prepared by adding a strong acid, like sulfuric acid to a metal peroxide, like barium peroxide. A method that allows the production of larger amounts of hydrogen peroxide involves the hydrolysis of a persulfate salt, like ammonium persulfate, which itself can be produced by the electrolysis of a solution of ammonium bisulfate in sulfuric acid.
Organic compounds, such as ethers, secondary alcohols or certain unsaturated hydrocarbons will produce unstable peroxides upon contact with air, process accelerated by light or heat, over the course of months or years. The autoxidation of said compounds produces both normal peroxides, as well as hydroperoxides, which are highly sensitive to heat or mechanical shock when dry. They have no use in chemistry and are a major issue when storing and purifying ethers, due to their explosive properties.[1]
Handling and safety
Peroxides are powerful oxidizing agents, thus they pose serious corrosive and fire hazard. Contact of naked skin with conc. hydrogen peroxide will cause white skin burns. Hydrogen peroxide reacts with acetone forming an unstable and very powerful explosive material. Thus, one must never discard hydrogen peroxide along with acetone or other ketones.
