Benzoyl peroxide – limbs retainer splint – foam cervical collar
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, a reaction that probably follows this stoichiometry:
2 C6H5C(O)Cl + BaO2 [C6H5C(O)]2O2 + BaCl2
Benzoyl peroxide is usually prepared by treating hydrogen peroxide with benzoyl chloride.
The oxygen-oxygen bond in peroxides is weak. Thus benzoyl peroxide readily undergoes homolysis (symmetrical scission), forming free radicals:
[C6H5C(O)]2O2 2C6H5CO2
The symbol indicates that the products are radicals, i.e. they contain an odd number of electrons. Such species are highly reactive. The homolysis is usually induced by heating. The half-life of benzoyl peroxide is one hour at 92 C. At 131 C, the half-life is one minute.
Benzoyl peroxide breaks down in contact with skin, producing benzoic acid and oxygen, neither of which is significantly toxic. 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.[citation needed]
Uses
Most benzoyl peroxide is used as a radical initiator to induce polymerizations. 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 2.5% is usually better tolerated. It commonly causes initial dryness and sometimes irritation, although the skin develops tolerance after a week or so. A small percentage of people are much more sensitive to it and liable to suffer burning, itching, peeling and possibly 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.[citation needed]
Other uses
Other common uses for benzoyl peroxide include 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).[citation needed]
In the U. S., the typical concentration for benzoyl peroxide is 2.5% to 10% for both prescription and over the counter preparations that are used in treatment for acne. Higher concentrations are used for hair bleach and teeth whitening. Benzoyl peroxide, like most peroxides, is a powerful bleaching agent. Contact with fabrics 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.[citation needed]
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.
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
^ Brodie, B. C. (1858), “Ueber die Bildung der Hyperoxyde organischer Sureradicale”, Justus Liebigs Ann. Chem. 108: 7983, doi:10.1002/jlac.18581080117 .
^ Li, Hui, III (1998), Synthesis, Characterization and Properties of Vinyl Ester Matrix Resins, Ph.D. Dissertation, University of Vermont, Chapter 2, http://scholar.lib.vt.edu/theses/available/etd-42198-113329/unrestricted/ch2.pdf .
^ Benzoyl peroxide, SIDS Initial Assessment Report, Geneva: United Nations Environment Programme, April 2004, http://www.inchem.org/documents/sids/sids/BENZOYLPER.pdf .
^ Klenk, Herbert; Gtz, Peter H.; Siegmeier, Rainer; Mayr, Wilfried (2005), “Peroxy Compounds, Organic”, Ullmann Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a19_199 .
^ Mills, O. H., Jr.; Kligman, A. M.; Pochi, P.; Comite, H. (1986), “Comparing 2.5%, 5%, and 10% benzoyl peroxide on inflammatory acne vulgaris”, Int. J. Dermatol. 25 (10): 66467, doi:10.1111/j.1365-4362.1986.tb04534.x, PMID 2948929 .
^ Yong, C. C. (1979), “Benzoyl peroxide gel therapy in acne in Singapore”, Int. J. Dermatol. 18 (6): 48588, doi:10.1111/j.1365-4362.1979.tb01955.x, PMID 158569 .
^ Leyden, James J.; Kligman, Albert M. (1977), Contact Dermatitis, 3, pp. 27375, doi:10.1111/j.1600-0536.1977.tb03674.x .
External links
International Chemical Safety Card 0225
NIOSH Pocket Guide to Chemical Hazards 0052
SIDS Initial Assessment Report from the Organisation for Economic Co-operation and Development (OECD)
“Benzoyl peroxide”, Re-evaluation of Some Organic Chemicals, Hydrazine and Hydrogen Peroxide, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans 71, Lyon, France: International Agency for Research on Cancer, 1999, pp. 34558, ISBN 92-832-1271-1, http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-13.pdf .
Benzoyl Peroxide
v d e
E numbers
Colours (E100199) Preservatives (E200299) Antioxidants & Acidity regulators (E300399) Thickeners, stabilisers & emulsifiers (E400499) pH regulators & anti-caking agents (E500599) Flavour enhancers (E600699) Miscellaneous (E900999) Additional chemicals (E11001599)
Waxes (E900909) Synthetic glazes (E910919) Improving agents (E920929) Packaging gases (E930949) Sweeteners (E950969) Foaming agents (E990999)
L-cysteine (E920) L-cystine (E921) Potassium persulfate (E922) Ammonium persulfate (E923) Potassium bromate (E924) Chlorine (E925) Chlorine dioxide (E926) Azodicarbonamide (E927) Carbamide (E927b) Benzoyl peroxide (E928)
v d e
Acne-treating agents (D10)
Antibacterial
Azelaic acid Benzoyl peroxide Blue light therapy Tea tree oil
Keratolytic
Glycolic acid Salicylic acid Sulfur Benzoyl peroxide
Anti-inflammatory
Aspirin Ibuprofen Red light therapy
Antibiotics
Clindamycin Dapsone Erythromycin Sulfacetamide Minocycline Tetracyclines
Hormonal
Antiandrogens Contraceptives
Retinoids
Adapalene Isotretinoin Tazarotene Tretinoin
Combinations
ZIANA Duac BenzaClin PLEXION Epiduo
Categories: Organic peroxides | IARC Group 3 carcinogens | Highly Hazardous ChemicalsHidden categories: All articles with unsourced statements | Articles with unsourced statements from February 2009 | Articles with unsourced statements from April 2009 | Articles with unsourced statements from March 2008
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