Peroxide

Peroxide

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

In organic chemistry, peroxide is a specific functional group or 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 hydroperoxide radical, and is thought to be involved in combustion of hydrocarbons in air.Organic peroxides tend to decompose easily to free radicals of the form:

:RO·

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 diamine are 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 metal slowly (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 spectroscopy screening method was developed. [http://pubs.acs.org/isubscribe/journals/cen/84/i04/html/8404scic.html]

Inorganic chemistry

In inorganic chemistry, peroxide is the anion O22−. 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 air or oxygen. Sodium peroxide Na2O2 is a typical example.

The peroxide ion contains two electrons more than the oxygen molecule. These two electrons, according to the molecular orbital theory, complete the two π* antibonding orbitals. This has as result a weakening of the bond strength of 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.

The oxides, peroxides and superoxides are closely related, forming a chain of oxygen ions of progressively higher oxidation number.

Barium peroxide is used in pyrotechnics and tracer ammunition, and was once used in the manufacture of hydrogen peroxide. Sodium peroxide is used as a carbon dioxide absorber and oxygen regenerator (e.g. in some submarines), through the reaction:

:2Na2O2 + 2CO2 → 2Na2CO3 + O2

See also

* catalase
* oxygen
* ozone
* peroxidases
* hydrogen peroxide
* carbamide peroxide
* sodium percarbonate
* calcium peroxide
* magnesium peroxide
* potassium monopersulfate
* sodium perborate monohydrate
* ozonide, O3
* superoxide, O2
* oxide, O2−
* dioxygenyl, O2+


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Look at other dictionaries:

  • peroxide — [pər äk′sīd΄] n. [ PER + OXIDE] any oxide containing the O2 group in which the two atoms of oxygen are linked by a single bond; specif., hydrogen peroxide vt. peroxided, peroxiding to treat with a peroxide; esp. to bleach (hair, etc.) with… …   English World dictionary

  • peroxide — ► NOUN 1) Chemistry a compound containing two oxygen atoms bonded together. 2) hydrogen peroxide, especially as used as a bleach for the hair. ► VERB ▪ bleach (hair) with peroxide …   English terms dictionary

  • peroxide — 1804, formed in English from per large amount + OXIDE (Cf. oxide). Peroxide blonde is attested from 1918 …   Etymology dictionary

  • Peroxide — Per*ox ide, n. (Chem.) An oxide containing more oxygen than some other oxide of the same element. Formerly peroxides were regarded as the highest oxides. Cf. {Per }, 2. [1913 Webster] …   The Collaborative International Dictionary of English

  • Peroxide — Die blau markierte Peroxidgruppe in (von oben nach unten) dem Peroxid Anion, sowie den oft instabilen Peroxiden im engeren Sinne, Hydroperoxiden und Peroxycarbonsäuren. R, R1 und R2 sind Organyl Reste (Alkyl Rest, Aryl Rest, Alkylaryl Rest etc.) …   Deutsch Wikipedia

  • peroxide — peroxidic /perr ok sid ik/, adj. /peuh rok suyd/, n., v., peroxided, peroxiding. n. 1. Chem. a. hydrogen peroxide, H2O2 or H O O H. b. a compound containing the bivalent group O2 , derived from hydrogen peroxide, as sodium peroxide, Na2O2, or… …   Universalium

  • peroxide — /pəˈrɒksaɪd / (say puh roksuyd) noun 1. Chemistry a. an oxide derived from hydrogen peroxide which contains the O O group; generally that oxide of an element or radical which contains an unusually large amount of oxygen. b. hydrogen peroxide,… …   Australian English dictionary

  • peroxide — I. noun Date: 1804 a compound (as hydrogen peroxide) in which oxygen is visualized as joined to oxygen • peroxidic adjective II. transitive verb ( ided; iding) Date: 1906 to treat with a peroxide; especially to bleach (hair) with hydrogen… …   New Collegiate Dictionary

  • Peroxide — Per|oxide,   Verbindungen des als Peroxogruppe, O O , vorliegenden Sauerstoffs mit Wasserstoff oder Metallen (anorganische Peroxide) oder mit organischen Resten (organische Peroxide). Technisch wichtige anorganische Peroxide sind neben dem… …   Universal-Lexikon

  • peroxide — n. & v. n. Chem. 1 a = hydrogen peroxide. b (often attrib.) a solution of hydrogen peroxide used to bleach the hair or as an antiseptic. 2 a compound of oxygen with another element containing the greatest possible proportion of oxygen. 3 any salt …   Useful english dictionary


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