Organic peroxide
2296644
223486302
2008-07-04T07:53:11Z
Tedmund
6887330
Reverted edits by [[Special:Contributions/210.211.234.177|210.211.234.177]] to last version by Chris the speller (using [[WP:HG|Huggle]])
[[Image:Peroxy-group.png|thumb|right|150px|The general structure of an organic peroxide.]]
[[Image:Hydroperoxide-group-2D.png|thumb|right|150px|The general structure of an organic hydroperoxide.]]
[[Image:Perester-2D-skeletal.png|thumb|right|150px|The general structure of a perester.]]
'''Organic peroxides''' are [[organic compound]]s containing the [[peroxide]] [[functional group]] (ROOR'). If the R' is hydrogen, the compound is called an '''organic hydroperoxide'''. '''Peresters''' have general structure RC(O)OOR.
The O-O bond easily breaks and forms [[free radical]]s of the form RO·. This makes organic peroxides useful as [[catalyst]]s for some types of [[polymerisation]], such as the [[epoxy]] [[resin]]s used in [[glass-reinforced plastic]]s. [[methyl ethyl ketone peroxide|MEKP]] and [[benzoyl peroxide]] are commonly used for this purpose. However, the same property also means that organic peroxides can either intentionally or unintentionally initiate explosive polymerisation in materials with unsaturated [[chemical bond]]s, and this process has been used in [[explosive material|explosives]].<ref>See for example the [[2006 transatlantic aircraft plot]].</ref>
Most organic peroxides are highly flammable, [[explosive material]]s, often powerful and volatile. As little as 5 milligrams of [[diethyl ether peroxide]] can shatter glass chemical apparatuses. Organic peroxides, like their inorganic counterparts, are powerful [[bleaching]] agents.
== Occurrence and use ==
Organic peroxides find numerous uses in various industries, as [[accelerator (chemistry)|accelerator]]s, [[activator]]s, [[catalyst]]s, [[cross-link]]ing agents, [[curing]] and [[vulcanization]] agents, [[hardener]]s, [[radical initiator|initiators]] and [[promoter]]s.
[[Methyl ethyl ketone peroxide]], [[benzoyl peroxide]] and to a much smaller degree [[acetone peroxide]] are used as [[radical initiator]]s for [[radical polymerization]] of some [[resin]]s, eg. [[polyester]] and [[silicone]], often encountered when making [[fiberglass]]. Methyl ethyl ketone peroxide can oxidize acetone to [[acetone peroxide]] (an explosive), so mixing it with [[acetone]] is discouraged. Polymerization initiators are usually supplied as dilute solutions, but even commercial products, especially the more concentrated ones, may form crystals around the lid when older, making the can shock-sensitive.
[[Pinane hydroperoxide]] is used in production of [[styrene-butadiene]] [[synthetic rubber]].
[[Benzoyl peroxide]] and [[acetone peroxide]] are used as [[flour bleaching agent|bleaching and "maturing" agents]] for treating [[flour]] to make its grain release [[gluten]] easier; the alternative is letting the flour slowly oxidize by air, which is too slow for the industrialized era.
[[Benzoyl peroxide]] is a highly effective topical medication for treating most forms of [[Acne vulgaris|acne]].
Cumene hydroperoxide is an intermediate in the [[cumene process]] of industrial synthesis of [[phenol]].
[[Acetone peroxide]] has become a favorite explosive of [[paramilitaries]], because of its easy manufacture, despite its instability. It is notorious for its susceptibility to heat, friction, and shock.
== Safety ==
Many [[organic chemical]]s form peroxides in presence of atmospheric [[oxygen]] and sometimes [[ultraviolet]] light; a typical example is the [[diethyl ether peroxide]]. As they combine unstably bound oxygen together with hydrogen and carbon in the same molecule, organic peroxides catch fire easily and burn rapidly and intensely. The same applies to organic materials contaminated with organic peroxides.
Since peroxides can form spontaneously in some materials, some caution must be exercised with such "peroxide forming materials". In addition, many liquid [[ether]]s in the presence of [[air]], light, and [[metal]] slowly (over a period of months) form ether hydroperoxides and peroxides (e.g. [[diethyl ether peroxide]]) which are extremely unstable. Consequently it is recommended that ether be stored over potassium hydroxide, which not only destroys peroxides but also acts as a powerful [[desiccator]] (drying agent). Extreme care must be taken with samples showing signs of crystal growth or precipitates. The ease with which [[diethyl ether]], [[tetrahydrofuran]] or [[dimethoxyethane|ethylene glycol dimethyl ether]] form explosive peroxides is the reason why they tend to be avoided in industrial processes.
Caution must be executed with mixing peroxide-forming materials with oxidizing agents. [[Acetone peroxide]], a powerful explosive, is an unwanted and dangerous byproduct of several chemical reactions, ranging from synthesis of [[MDMA]] (where it is a [[by-product]] of [[safrole|isosafrole]] oxidation in acetone) to industrial production of [[phenol]] (where the second product of the [[cumene process]], [[acetone]], is partially oxidized to peroxide on the second reaction step).
Accidental preparation of organic peroxides can occur by mixing ketone solvents (most commonly acetone) with waste materials containing [[hydrogen peroxide]] or other oxidizers and leaving the mixture standing for several hours.
Organic peroxides tend to react with metals. [[Glass]], [[stainless steel]], [[polyethylene]] or [[teflon]] containers are suggested for handling and storage; steel, copper alloys, rubber, lead, etc. should not be used. Empty containers must be washed with water immediately.
Organic peroxides must not be directly mixed with materials containing heavy metal ions like iron, cobalt or manganese, as these promote the decomposition of the peroxides. Direct mixing with [[amine]] compounds should be avoided as well. When mixing peroxides with amines (e.g., when making polyamides), both the peroxide and the amine have to be diluted separately with the monomer; the diluted chemicals can then be mixed.
Spillages of small amounts of organic peroxides can be wiped off with a rag, which then has to be disposed by burning at a safe place. Materials with absorbed organic peroxides must be saturated with water when stored.
Organic peroxides are sensitive to light and have to be stored in darkness. Some decompose at room temperature and release gaseous products; gas ejectors on the lids of the containers are required. Based on the [[Self Accelerating Decomposition Temperature]], some peroxides have to be stored refrigerated.
In case of a fire, an explosion can be anticipated. A foam [[fire extinguisher]] can be used for small fires.
Small amounts of organic peroxides can be disposed of by careful burning of a substance diluted to under 10% or hydrolyzed. For hydrolysis, using a solution consisting of 80 parts water, 20 parts [[sodium hydroxide]], and 0.3 parts [[surfactant]] to allow easier wetting of the crystals of the peroxide. The recommended amount of the solution is 10 times the weight of the peroxide. The peroxide has to be slowly poured into the solution, with constant stirring to avoid local overheating. The reaction is slightly [[exothermic]], but additional cooling is not required. The reaction is slow, and requires stirring for some 12 to 24 hours; the peroxide can then be considered decomposed.
== Synthesis ==
Peroxides can be synthesized in the laboratory in a number of ways:
* peroxy acids by [[oxidation]] of [[carboxylic acid]]s with [[hydrogen peroxide]]
* peroxy acids by oxidation and hydrolysis of [[Grignard reagent]]s
* peroxides by [[photooxidation]] of [[diene]]s
* peroxides by [[oxymercuration]] of [[alkene]]s followed by reaction with a hydroperoxide
* peroxy acids by reaction of [[alkyl halide]]s with hydrogen peroxide
==Reactions ==
Some peroxide reactions are:
* [[organic reduction]] to [[alcohol]]s with [[lithium aluminium hydride]] or [[phosphite ester]]s
* cleavage to ketones and alcohols in the base catalyzed [[Kornblum–DeLaMare rearrangement]]
== See also ==
* [[Peroxide]]
* [[Peroxyacid]]
* [[Peroxyacyl nitrates]]
* [[Ozonide]]
== External links ==
* [http://www.ccohs.ca/oshanswers/chemicals/organic/organic_peroxide.html OSH Answers - organic peroxides]
* [http://www.carolina.com/chemistry/resources/peroxides.asp Carolina Biological: The Perils of Peroxides]
* [http://www.nof.co.jp/english/business/chemical/product01_06.html Peroxide disposal]
==References==
<References />
{{Functional group}}
[[Category:Organic peroxides| ]]
[[Category:functional groups]]
[[fa:پراکسید آلی]]
[[ja:ペルオキシド]]