A peroxide is a polyatomic anion with the molecular formula O22. Compounds are generally classified as ionic or covalent or as organic and inorganic. The OO group is called the peroxo group or peroxide group.
Peroxide also refers to any compound that contains the peroxide anion.
Hydrogen peroxide, H2O2, is a simple peroxide compound. Other inorganic peroxides are known (apart from hydrogen peroxide). These are classified as ionic peroxides or as covalent peroxides. Ionic peroxides contain alkali metal ions or alkaline earth ions as their cations. Covalent peroxides include hydrogen peroxide and also peroxymonosulfuric (H2SO5).
Technically, superoxides, ozones, ozonides are peroxide compounds, but they tend to be considered separate due to their special characteristics.
Peroxides occur naturally in small amounts in plants and animals, water, and the atmosphere. In humans and other animals, hydrogen peroxide is a by-product of biochemical reactions. The chemical is short-lived, but is toxic to cells due to its ability to oxidize membrane DNA, proteins, and lipids. This toxicity makes peroxide useful as a disinfectant, killing bacteria and other pathogens. However, almost all eukaryotic cells deliberately form peroxide in organelles called peroxisomes. The peroxisomes are used for catabolism of fatty acids, D-amino acids and polyamines and biosynthesis of essential compounds for pulmonary function and normal brain.
The enzyme catalase uses peroxide to oxidize substrates to neutralize toxins in the kidney and liver cells. In this way, for example, humans are able to metabolize ethanol to acetaldehyde.
Plants use hydrogen peroxide as a signaling chemical that indicates defense against pathogens.
Some peroxides can discolor organic molecules, which is why they are added to cleaning agents and hair coloring agents.
Peroxides are widely used to synthesize drugs and other chemicals.
The bombadier beetle stores hydroquinone and hydrogen peroxide in abdominal stores. When the beetle is threatened, it mixes the chemicals together, resulting in an exothermic reaction that allows the beetle to squirt the boiling, smelly liquid at a threat.
Most people are familiar with hydrogen peroxide solution, which is a dilute solution of hydrogen peroxide in water. While household peroxide is a safe chemical, concentrated peroxide is extremely dangerous!
Peroxides are powerful oxidants, capable of causing serious chemical burns. Peroxide compounds should be stored in opaque containers, in cool, vibration-free places. The heat and light accelerate chemical reactions with peroxides and should be avoided.
