Benzoyl Peroxide 

Benzoyl peroxide is a powerful organic compound used in skincare products, particularly for treating acne with molecular formula $C_{14}{H}_{10}{O}_4.$

It is known to work by the removal of bacteria on the skin. It helps prevent the skin pores from getting clogged and the shedding of dead skin cells. It also has bleaching properties, which in some ways make it useful in cleaning and as a polymerization initiator in various industrial applications.

1.0Benzoyl Peroxide Structure

• Benzoyl peroxide structure has two benzoyl groups (C₆H₅CO–) on both sides linked via a peroxide bond (–O–O–). 
• It also contains two carbonyl groups (C=O) and two oxygen atoms connected by a peroxide linkage on both sides of the compound. 
• The following structure can be represented as: 

$C_6{H}_{5}CO-O-O-CO{C}_6{H}_5$

2.0Preparation of Benzoyl Peroxide

Benzoyl peroxide can be synthesized by different methods, of which the most common ones are as follows:

1. Peroxidation of Benzoyl Hydroperoxide: This is the reaction of benzoyl hydroperoxide with a catalyst, usually an acid, that forms benzoyl peroxide. This is one of the more direct methods of synthesizing benzoyl peroxide.

$C_6{H}_{5}COOH(benzoylhydroperoxide)\to C_6{H}_{5}C{O}_{2}O+H_{2}O$

2. Reaction of Benzoyl Chloride with Hydrogen Peroxide: In this reaction, benzoyl chloride reacts with hydrogen peroxide in the presence of a suitable base or catalyst. As a by-product, this reaction gives benzoyl peroxide and hydrochloric acid.

$C_6{H}_{5}COCl(benzoylchloride)+H_2{O}_2\to C_6{H}_{5}C{O}_{2}O+HCl$

3. Direct Synthesis from Benzoyl Hydroperoxide: This technique includes the thermolysis of benzoyl hydroperoxide, which gives benzoyl peroxide. The reaction is performed at a controlled temperature and pressure.

$C_6{H}_{5}C{O}_{2}OH(benzoylhydroperoxide)\to C_6{H}_{5}C{O}_{2}O+H_{2}O$

4. Autoxidation of Benzene: This industrial process involves oxidizing benzene to produce benzoyl peroxide. It generally takes place at high temperatures, with catalysts initiating the reaction.

$C_6{H}_6(benzene)+O_2\to C_6{H}_{5}C{O}_{2}O$

5. Electrochemical Synthesis: This process involves the oxidation of benzoyl compounds using electrochemical cells and results in the formation of benzoyl peroxide. This method is under further research in terms of efficiency and scale.

$C_6{H}_{5}COOH(benzoylhydroperoxide)\to C_6{H}_{5}C{O}_{2}O$

3.0Properties Of Benzoyl Peroxide

1. Physical Properties:

• Physical Appearance: White crystalline solid or powder.
• Molecular Weight: 242.23 g/mol.
• Melting Point: 103°C.
• Boiling Point: 254°C.
• Solubility: Insoluble in water but soluble in organic solvents like acetone, benzene, and ether.
• Stability: Benzoyl peroxide is unstable at high temperatures and decomposes to release oxygen and benzoyl radicals.

2. Chemical Properties: 

• Decomposition: Benzoyl peroxide, when exposed to heat, light, or a catalyst, produces benzoic acid and oxygen: 

$C_6{H}_{5}CO-O-O-CO{C}_6{H}_5\to 2C_6{H}_{5}COOH+O_2$

• Free Radical Formation: Benzoyl peroxide can start free radical polymerization reactions; it can generate benzoyloxyl radicals (C₆H₅COO–).

4.0Benzoyl Peroxide Uses

• Acne treatment: This is one of the common uses of benzoyl peroxide in treating acne. It kills Propionibacterium acnes, a bacterium that causes acne, and helps reduce comedone formation.
• Polymerization: Benzoyl peroxide is used as a polymerization initiator for monomers such as styrene and acrylonitrile to produce plastics and resins.
• Bleaching Agent: It is used as a bleaching agent in the textile industry and has been incorporated into hair bleach.
• Radical Generator: In industrial processes, benzoyl peroxide is used to produce radicals for radical substitution and chain polymerization reactions.

5.0Side-Effects of Benzoyl Peroxide

• Skin Irritation: It can cause redness, peeling, dryness, or a burning sensation, especially when starting a skin treatment or using it too frequently.
• Dryness: Benzoyl peroxide removes moisture from the skin, which may result in flakiness or tightness.
• Increased Sensitivity to Sunlight: It may cause sensitivity to sunlight, increasing the chances of sunburn. It is advised to use sunscreen during treatment.
• Allergic Reactions: Hives, itching, or swelling are signs of an allergy to the product.
• Bleaching Effect: Benzoyl peroxide can bleach hair, clothing, and bedding if it comes in contact with them.
• Peeling and Cracking: Overuse can lead to peeling, cracking, or excessive dryness, which might cause discomfort or exacerbate any existing skin problems.