A peroxide is a compound containing an
oxygen-oxygen single bond. The simplest stable peroxide is hydrogen peroxide. Superoxides, dioxygenyls, ozones and ozonides compound are considered separately. __NOTOC__
organic chemistry, peroxide is a specific functional groupor a molecule containing an oxygen-oxygen single bond (R-O-O-R'). When the other oxygen bears a hydrogen, it is called a hydroperoxide (R-O-O-H). The radical HOO· is known as hydroperoxideradical, and is thought to be involved in combustionof hydrocarbons in air.Organic peroxides tend to decompose easily to free radicals of the form:
This makes them useful as
catalysts for some types of polymerisation, such as the polyester resins used in glass-reinforced plastics. MEKP( methyl ethyl ketone peroxide) is commonly used for this purpose.
However, the same property also means that organic peroxides can accidentally initiate explosive polymerization in materials with unsaturated
chemical bonds. Since peroxides can form spontaneously in some materials, some caution must be exercised with such "peroxide-forming materials." Triacetone triperoxide(TATP) and hexamethylene triperoxide diamineare explosive organic peroxide compounds; TATP may be formed accidentally as a waste product in some reactions. In addition, many liquid ethers in the presence of air, light, and metalslowly (over a period of months) form ether peroxides (e.g., diethyl ether peroxide), which are extremely unstable. As a consequence, it is recommended that ether be stored over potassium hydroxide, which not only destroys peroxides but also acts as a powerful desiccant. Extreme care must be taken with samples showing signs of crystal growth or precipitates.
TATP is an easily synthesized, inexpensive, explosive compound that is difficult to detect by normal screening methods. Consequently, it is an explosive favored by terrorists. TATP was used in the 2005 London Underground bombings and the 2001 "shoe bomber." In 2002, a simple
mass spectroscopyscreening method was developed. [http://pubs.acs.org/isubscribe/journals/cen/84/i04/html/8404scic.html]
inorganic chemistry, peroxide is the anionO22−. It is highly basic, and present in ionic compounds. Pure peroxides (containing only cations and the peroxide anions) are usually formed by burning alkali metals or alkaline earth metals in airor oxygen. Sodium peroxideNa2O2 is a typical example.
The peroxide ion contains two
electrons more than the oxygen molecule. These two electrons, according to the molecular orbitaltheory, complete the two π* antibonding orbitals. This has as result a weakening of the bond strengthof the peroxide ion and a greater length for the bond O-O : Li2O2 130 pm to BaO2 147 pm. Furthermore, the peroxide ion is diamagnetic.
The peroxides of the alkali metals and Ca, Sr and Ba are ionic. The peroxides of a number of electropositive metals such as Mg, the lanthanides and the uranyl-ion show an intermediary character, between ionic and
covalent. The peroxides of metals such as Zn, Cd and Hg are mainly covalent.
Peroxides are powerful oxidizers, and usually fairly unstable. Ionic peroxides react with water and diluted acids to form hydrogen peroxide. Organic compounds are oxidized to carbonates, even at normal temperatures. Sodium peroxide is a powerful oxidator of metals, such as iron.
oxides, peroxides and superoxides are closely related, forming a chain of oxygen ions of progressively higher oxidation number. Barium peroxideis used in pyrotechnicsand tracer ammunition, and was once used in the manufacture of hydrogen peroxide. Sodium peroxideis used as a carbon dioxideabsorber and oxygen regenerator (e.g. in some submarines), through the reaction:
:2Na2O2 + 2CO2 → 2Na2CO3 + O2
sodium perborate monohydrate
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