Benzoyl peroxide

Benzoyl peroxide

Skeletal formula
Ball-and-stick model
Names
IUPAC name dibenzoyl peroxide
Other names Benzoyl peroxide (BPO) Benzoperoxide Dibenzoyl peroxide (DBPO)
Identifiers
CAS Number	94-36-0 Y
ChEMBL	ChEMBL1200370 N
ChemSpider	6919 Y
EC Number	202-327-6
Jmol 3D model	Interactive image
KEGG	D03093 Y
PubChem	7187
RTECS number	DM8575000
UNII	W9WZN9A0GM Y
InChI InChI=1S/C14H10O4/c15-13(11-7-3-1-4-8-11)17-18-14(16)12-9-5-2-6-10-12/h1-10H Y Key: OMPJBNCRMGITSC-UHFFFAOYSA-N Y 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 Key: OMPJBNCRMGITSC-UHFFFAOYAV
SMILES c1ccc(cc1)C(=O)OOC(=O)c2ccccc2
Properties
Chemical formula	C14H10O4
Molar mass	242.23 g·mol−1
Appearance	colourless solid
Density	1.334 g/cm3
Melting point	103 to 105 °C (217 to 221 °F; 376 to 378 K) decomposes
Solubility in water	poor
Pharmacology
ATC code	D10AE01 QD11AX90 (WHO)
Vapor pressure	{{{value}}}
Supplementary data page
Structure and properties	Refractive index (n), Dielectric constant (εr), etc.
Thermodynamic data	Phase behaviour solid–liquid–gas
Spectral data	UV, IR, NMR, MS
N verify (what is YN ?)
Infobox references

Benzoyl peroxide (BPO) is an organic compound in the peroxide family. It consists of two benzoyl groups bridged by a peroxide link. Its structural formula is [C₆H₅C(O)]₂O₂. 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 bleaching flour, hair and teeth, for cross-linking polyester resins, and for many other purposes.

It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system.

Uses

Most benzoyl peroxide is used as a radical initiator to induce polymerizations. Other major applications include its antiseptic and bleaching properties.

Acne treatment

Tube of a water-based 5% benzoyl peroxide preparation for the treatment of acne.

Benzoyl peroxide (BPO) is effective for reducing the number and severity of acne lesions. BPO has a bactericidal effect on Propionibacterium acnes bacteria associated with acne and does not induce antibiotic resistance. It may be combined with salicylic acid, sulfur, erythromycin or clindamycin (antibiotics), or adapalene (a synthetic retinoid). Two common combination drugs include benzoyl peroxide/clindamycin and adapalene/benzoyl peroxide, an unusual formulation considering most retinoids are deactivated by peroxides. Combination products such as benzoyl peroxide/clindamycin and benzoyl peroxide/salicylic acid appear to be slightly more effective than benzoyl peroxide alone for the treatment of acne lesions.

Benzoyl peroxide for acne treatment is typically applied to the affected areas in gel or cream form, in concentrations of 2.5% increasing through 5.0%, and up to 10%. No strong evidence supports the idea that higher concentrations of benzoyl peroxide are more effective than lower concentrations.

Benzoyl peroxide 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 and gaining tolerance at a higher level may give better subsequent acne clearance. Irritation can also be reduced by avoiding harsh facial cleansers and wearing sunscreen prior to sun exposure.

Other uses

Other common uses for benzoyl peroxide include

• Bleaching hair
• Tooth whitening systems
• The preparation of bleached flour
• A initiator and catalyst for polyester thermoset resins, as an alternative to the much more hazardous methyl ethyl ketone peroxide.
• A hardener in order to start the polymerization process in resins. For instance, PMMA resins can be polymerized with benzoyl peroxide.
• Removing ink and dye stains on vinyl dolls and other playscale figures.

In the U.S., the typical concentration for benzoyl peroxide is 2.5% to 10% for both 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 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.

Side effects

Concentrated benzoyl peroxide is potentially explosive, and can cause fires without external ignition. The hazard is acute for the pure material, so the compound is generally used as a solution or a paste. For example, cosmetics contain only a small percent of benzoyl peroxide and pose no explosion risk.

Studies have highlighted the carcinogenic potential of benzoyl peroxide. A 1981 study from the journal Science concluded, "caution should be recommended in the use of this and other free radical-generating compounds".

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.

• BenzoperoxideRx.JPG

  Skin irritation due to benzoyl peroxide

• Benzoyl peroxide stain.jpg

  A bleached fabric stain caused by contact with benzoyl peroxide.

Synthesis, structure and 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 equation:

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 fission), forming free radicals:

[C₆H₅C(O)]₂O₂ → 2 C₆H₅CO₂^•

The symbol ^• 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 °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.

External links

• International Chemical Safety Card 0225
• SIDS Initial Assessment Report from the Organisation for Economic Co-operation and Development (OECD)
• .