Peroxy acid
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2008-04-10T13:16:23Z
Edgar181
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{{Double image stack|right|Acetic-acid-2D-skeletal.svg|peracetic acid.png|100|Comparison of an acid ([[acetic acid]], top) and a peroxy acid ([[peracetic acid]], bottom)}}
A '''peroxy acid''' (often spelled as one word, '''peroxyacid''', and sometimes called '''peracid''') is an [[acid]] in which an acidic -OH group has been replaced by an -OOH group. They are formed chiefly by elements in [[carbon group|groups 14]], [[nitrogen group|15]] and [[Chalcogen|16]] of the [[periodic table]], though [[boron]] and certain [[transition element]]s are also known to form peroxy acids. [[Sulfur]] and [[phosphorus]] form the largest range of peroxy acids, including some condensed form such as peroxydiphosphoric acid, H<sub>4</sub>P<sub>2</sub>O<sub>8</sub> and peroxydisulfuric acid, H<sub>2</sub>S<sub>2</sub>O<sub>8</sub>.
Because they are generally very powerful oxidizing agents, most peroxyacids are prepared by [[electrolysis|electrolytic oxidation]] of ordinary oxyacids. Typically a high [[current density]] must be used to form the peroxyacid in good yield: the electrolysis of [[sulfuric acid]] being the most important example. Peroxy acids are generally not very stable in solution and decompose to ordinary oxyacids and oxygen, but relatively more stable anhydrous forms can be made by reacting [[hydrogen peroxide]] with [[chlorosulfonic acid]] or [[phosphoryl chloride]].
All peroxy acids are very powerful [[oxidizing agent]]s. Some such acids are peroxy-[[carboxylic acid]]s, such as [[Meta-Chloroperoxybenzoic acid|''meta''-chloroperoxybenzoic acid]] (mCPBA), which is used as a [[reagent]] in the [[Baeyer-Villiger oxidation]] and in oxidation of [[carbon]]-carbon [[double bond]]s in [[alkene]]s to generate [[epoxide]]s (oxiranes). Sodium peroxy carbonate, Na<sub>2</sub>CO<sub>4</sub>, is widely used as a household [[bleach]]ing agent for textiles, whilst sodium, potassium and ammonium peroxydisulfates (Na<sub>2</sub>S<sub>2</sub>O<sub>8</sub>, K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> and (NH<sub>4</sub>)<sub>2</sub>S<sub>2</sub>O<sub>8</sub>) are widely used as general purpose oxidizing agents in the laboratory.
== See also ==
* [[Organic peroxide]]
* [[Meta-Chloroperoxybenzoic_acid]]
* [[Peroxyacetic acid]], {{carbon}}{{hydrogen}}<sub>3</sub>{{carbon}}(={{oxygen}}){{oxygen}}{{oxygen}}{{hydrogen}}
* [[Peroxyacyl nitrates]]
[[Category:Oxidizing agents]]
[[Category:Peroxy acids| ]]
[[ja:過酸]]
[[fr:Peracide]]