Organic compound Benzoyl peroxide is an organic compound in the peroxide family. It consists of two benzoyl groups bridged by aperoxide link. Name : Ragia Mohamed Hamada Class: 11 A

Benzoyl peroxide

Benzoyl

peroxide (pron.: /ˈbɛnzɔɪl pəˈrɒksaɪd/) is an organic compound in

the peroxide family. It consists of two benzoyl groups bridged by

aperoxide 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 improving flour, for bleaching hair and teeth, for polymerising

polyester and many other uses.

Benzoyl peroxide is included in the World Health Organization (WHO) Model Lists of Essential

medicines, 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, 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. 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 disproportionates to form harmless products such as sodium chloride.

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 works as a peeling agent. It increases skin turnover, clearing pores and

reducing the bacterial count (specifically P. acnes) as well as acting directly as an

antimicrobial.[5]

It may be combined with salicylic

acid, sulfur, erythromycin or clindamycin (antibiotics), and adapalene (a

synthetic retinoid). Two common combination drugs include benzoyl

peroxide/clindamycin and adapalene/benzoyl peroxide, a unique formulation considering

most retinoids are deactivated by peroxides.

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%, and up to 10%. Research

suggests that 5% and 10% concentrations are not significantly more effective than 2.5%,

while 2.5% is usually better tolerated, though the majority of major studies comparing it to

other treatments use the higher 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.

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 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. In the paint industry,

benzoyl peroxide is used as a hardener in order to start the polymerization process in

resins. For instance, PMMA resins can be polymerized with benzoyl peroxide.

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.

1 2

1 -Skin irritation due to benzoyl peroxide

2- A bleached fabric stain caused by contact with benzoyl peroxide.

Safety

Concentrated 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,

the compound is generally used as a solution or a paste. For example, cosmetics contain

only a few 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".