View source for Benzoyl peroxide

{{chembox
| Watchedfields = changed
| verifiedrevid = 321988526
| ImageFile = Benzoyl-peroxide.svg
| ImageName = Skeletal formula
| ImageFile1 = Benzoyl-peroxide-3D-balls.png
| ImageName1 = Ball-and-stick model
| IUPACName = dibenzoyl peroxide
|   OtherNames = benzoyl peroxide
| Section1 = {{Chembox Identifiers
|   InChI=1/C14H10O4/c15-13(11-7-3-1-4-8-11)17-18-14(16)12-9-5-2-6-10-12/h1-10H
|   InChIKey = OMPJBNCRMGITSC-UHFFFAOYAV
| CASNo = 94-36-0
|    CASNo_Ref = {{cascite}}
|   EC-number = 202-327-6
|   ChemSpiderID = 6919
|   PubChem = 7187
|   ATCCode_prefix = D10
|   ATCCode_suffix = AE01
|   ATC_Supplemental = {{ATCvet|D11|AX90}}
|   RTECS = DM8575000
|   SMILES = O=C(OOC(=O)c1ccccc1)c2ccccc2
  }}
| Section2 = {{Chembox Properties
|   C=14|H=10 |O=4 
|   MolarMass = 242.23 g/mol
|   Appearance = colourless solid
|   Density = 1.334 g/cm<sup>3</sup>
|   MeltingPt = 103–105 °C decomp.
|   Solubility = poor
  }}
| Section7 = {{Chembox Hazards
|   EUIndex = 617-008-00-0
|   EUClass = Explosive ('''E''')<br/>Irritant ('''Xi''')
|   RPhrases = {{R3}}, {{R7}}, {{R36}}, {{R43}}
|   SPhrases = {{S2}}, {{S3/7}}, {{S14}}, {{S36/37/39}}
|   NFPA-H = 3
|   NFPA-F = 1
|   NFPA-R = 3
|   NFPA-O = ox
|   Autoignition = 80 °C
  }}
}}
[[Image:Benzoyl peroxide gel.jpg|thumb|right|200px|Tube of Basiron, a water-based 5% benzoyl peroxide preparation for the treatment of [[Acne vulgaris|acne]].]]
[[Image:Benzoyl peroxide stain.jpg|thumb|right|200px|A bleached fabric stain caused by contact with a benzoyl peroxide-based consumer product.]]
'''Benzoyl peroxide''' ({{pronEng|ˈbɛnzɔɪl pəˈrɒksaɪd}}) is an [[organic compound]] in the [[organic peroxide|peroxide]] family. It consists of two benzoyl groups bridged by a [[peroxide]] link.  Its [[structural formula]] is [C<sub>6</sub>H<sub>5</sub>C(O)]<sub>2</sub>O<sub>2</sub>.  It is one of the most important organic peroxides in terms of applications and the scale of its production.  Benzoyl peroxide is used as an acne treatment, for improving flour, for bleaching hair and teeth, for polymerising polyester and many other uses.

Benzoyl peroxide is included in the World Health Organization's "Essential Drugs List", which is a list of minimum medical needs for a basic health care system.

==Synthesis, structure, physical properties==
Benzoyl peroxide was the first organic peroxide prepared by intentional synthesis.  It was prepared by treating [[benzoyl chloride]] with [[barium peroxide]],<ref>{{citation | first = B. C. | last = Brodie | title = Ueber die Bildung der Hyperoxyde organischer Säureradicale | journal = Justus Liebigs Ann. Chem. | year = 1858 | volume = 108 | pages = 79–83 | doi = 10.1002/jlac.18581080117}}.</ref> a reaction that probably follows this [[stoichiometry]]:
:2 C<sub>6</sub>H<sub>5</sub>C(O)Cl  +  BaO<sub>2</sub>   →   [C<sub>6</sub>H<sub>5</sub>C(O)]<sub>2</sub>O<sub>2</sub>  +  BaCl<sub>2</sub>
Benzoyl peroxide is usually prepared by [[chemical reaction|treating]] [[hydrogen peroxide]] with [[benzoyl chloride]]. 

The oxygen-oxygen bond in peroxides is weak.  Thus benzoyl peroxide readily undergoes [[homolysis]] (symmetrical scission), forming [[radical (chemistry)|free radicals]]:
:[C<sub>6</sub>H<sub>5</sub>C(O)]<sub>2</sub>O<sub>2</sub> → 2 C<sub>6</sub>H<sub>5</sub>CO<sub>2</sub><sup>•</sup>
The symbol <sup>•</sup> indicates that the products are radicals; i.e., they contain at least one unpaired electron.  Such species are highly reactive.  The homolysis is usually induced by heating. The [[half-life]] of benzoyl peroxide is one hour at 92&nbsp;°C. At 131&nbsp;°C, the half-life is one minute.<ref>{{citation | first = Hui, III | last = Li | title = Synthesis, Characterization and Properties of Vinyl Ester Matrix Resins | url = http://scholar.lib.vt.edu/theses/available/etd-42198-113329/unrestricted/ch2.pdf | series = Ph.D. Dissertation, University of Vermont | volume = Chapter 2 | date = 1998}}.</ref>

Benzoyl peroxide breaks down in contact with skin, producing [[benzoic acid]] and oxygen, neither of which is significantly toxic.<ref>{{SIDS-ref | title = Benzoyl peroxide | id = BENZOYLPER | date = April 2004}}.</ref> It is important to note that the safety of the decomposition products does not mean that the substance itself is safe, as it is benzoyl peroxide's action as an oxidizing agent that is of importance. Hydrogen peroxide can be corrosive due to its oxidizing properties, but decomposes to form water and oxygen. [[Sodium hypochlorite]] (commonly known as "bleach") also shares these properties, but decomposes to form harmless products such as [[sodium chloride]].{{Fact|date=February 2009}}

== Uses ==
Most benzoyl peroxide is used as a [[radical initiator]] to induce polymerizations.<ref>{{Ullmann | first1 = Herbert | last1 = Klenk | first2 = Peter H. | last2 = Götz | first3 = Rainer | last3 = Siegmeier | first4 = Wilfried | last4 = Mayr | title = Peroxy Compounds, Organic | doi = 10.1002/14356007.a19_199}}.</ref>  Other major applications include its antiseptic and bleaching properties.

===Acne treatment===
Benzoyl peroxide for [[acne]] treatment is typically applied to the affected areas in gel or cream form, in concentrations of 2.5% increasing through the usually effective 5% to up to 10%. Research suggests that 5 and 10% concentrations are not significantly more effective than 2.5%, and that 2.5% is usually better tolerated.<ref>{{citation | last1 = Mills | first1 = O. H., Jr. | last2 = Kligman | first2 = A. M. | last3 = Pochi | first3 = P. | last4 = Comite | first4 = H. | year = 1986 | title = Comparing 2.5%, 5%, and 10% benzoyl peroxide on inflammatory acne vulgaris | journal = Int. J. Dermatol. | volume = 25 | issue = 10 | pages = 664–67 | pmid = 2948929 | doi = 10.1111/j.1365-4362.1986.tb04534.x}}.</ref><ref>{{citation | last = Yong | first = C. C. | year = 1979 | title = Benzoyl peroxide gel therapy in acne in Singapore | journal = Int. J. Dermatol. | volume = 18 | issue = 6 | pages = 485–88 | pmid = 158569 | doi = 10.1111/j.1365-4362.1979.tb01955.x}}.</ref> It commonly causes initial dryness and sometimes irritation, although the [[skin]] develops [[Drug tolerance|tolerance]] after a week or so.  A small percentage of people are much more [[Hypersensitivity|sensitive]] to it and liable to suffer burning, [[itching]], peeling and possibly [[Swelling (medical)|swelling]]. It is sensible to apply the lowest concentration and build up as appropriate. Once tolerance is achieved, increasing the quantity or concentration a second time and gaining tolerance at a higher level usually gives better subsequent acne clearance. Benzoyl peroxide works as a peeling agent, increasing skin turnover and clearing pores, thus reducing the bacterial count there as well as directly as an antimicrobial.{{Fact|date=April 2009}}

===Other uses===

Other common uses for benzoyl peroxide include [[hair dye|dyeing hair]], and as an active ingredient in [[teeth]] whitening systems. It is also used in the preparation of [[flour]], and can be used as an [[initiator]] and  [[catalyst]] for [[polyester]] [[thermoset]] resins (as an alternative to the much more hazardous [[methyl ethyl ketone peroxide]]).{{Fact|date=April 2009}}

In the [[United States of America|U. S.]], the typical concentration for benzoyl peroxide is 2.5% to 10% for both [[Prescription drug|prescription]] and [[over-the-counter drug]] preparations that are used in treatment for acne.  Higher concentrations are used for hair bleach and teeth whitening. Benzoyl peroxide, like most [[peroxide]]s, is a powerful [[bleach|bleaching agent]]. Contact with [[fabric]]s or [[hair]] can cause permanent color dampening almost immediately. Even secondary contact can cause bleaching. For example, contact with a towel that has been used to wash off benzoyl peroxide-containing hygiene products.{{Fact|date=March 2008}}

==== Adverse effects ====
In a 1977 study using a human maximization test, 76% of subjects acquired a contact sensitization to benzoyl peroxide.  Formulations of 5% and 10% were used.<ref>{{citation | unused_data = DUPLICATE DATA: title = Contact Dermatitis | first1 = James J. | last1 = Leyden | first2 = Albert M. | last2 = Kligman | year = 1977 | title = Contact sensitization to benzoyl peroxide | volume = 3 | issue = 5 | pages = 273–75 | doi = 10.1111/j.1600-0536.1977.tb03674.x | journal = Contact Dermatitis}}.</ref>

== Safety ==
Unlike most organic compounds, benzoyl peroxide is potentially explosive, and, hence, it can cause fires without external ignition.  The hazard is acute for the pure material, and for this reason, in commerce the compound is usually used as a solution or a paste.  For example, cosmetics contain only a few percent of benzoyl peroxide and, thus, pose no explosion risk.

== References ==
{{reflist}}

== External links ==
*{{ICSC|0225|02}}
*{{PGCH|0052}}
*{{SIDS | title = Benzoyl peroxide | id = BENZOYLPER}}
*{{citation | contribution = Benzoyl peroxide | url = http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-13.pdf | pages = 345–58 | title = Re-evaluation of Some Organic Chemicals, Hydrazine and Hydrogen Peroxide  | series = IARC Monographs on the Evaluation of Carcinogenic Risks to Humans 71 | publisher = International Agency for Research on Cancer | location = Lyon, France | year = 1999 | isbn = 92-832-1271-1}}.
*[http://www.chemicalland21.com/arokorhi/specialtychem/finechem/BENZOYL%20PEROXIDE.htm Benzoyl Peroxide]

{{E number infobox 920-929}}
{{Acne Agents}}

[[Category:Organic peroxides]]
[[Category:IARC Group 3 carcinogens]]

[[Category:Anti-acne preparations]]
[[Category:Acne treatments]]

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[[fr:Peroxyde de benzoyle]]
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[[ja:過酸化ベンゾイル]]
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[[pt:Peróxido de benzoíla]]
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[[zh:过氧化苯甲酰]]
[[Category:2Fix]]