Organic peroxide

Organic peroxides are organic compounds containing the peroxide functional group (ROOR'). If the R' is hydrogen, the compound is called an organic hydroperoxide. Peresters have general structure RC(O)OOR. The O−O bond easily breaks, producing free radicals of the form RO•. This makes organic peroxides useful as initiators for some types of polymerization, such as the epoxy resins used in glass-reinforced plastics.

Structure and Reactivity

Organic peroxides are often unstable and reactive compounds, due to their weak O−O bond. They can undergo homolytic cleavage, generating two free radical species which can initiate polymerization reactions. This property is exploited in the production of various polymers, as well as in the curing of polyester resins. The reactivity of organic peroxides can be influenced by the presence of substituents on the carbon atoms adjacent to the peroxide group. Electron-withdrawing groups tend to make the peroxide more stable, while electron-donating groups increase its reactivity.

Safety

Due to their instability, organic peroxides can pose significant safety hazards, including the risk of fire and explosion. They are sensitive to shock, heat, and friction, which can trigger violent decomposition. The handling and storage of organic peroxides require special precautions to minimize these risks. Safety measures include storing them at low temperatures, away from sources of ignition, and in compliance with regulations that pertain to explosive and flammable chemicals.

Uses

Organic peroxides serve a wide range of applications in the chemical industry. They are primarily used as initiators in the polymerization of ethylene, styrene, and vinyl chloride, leading to the production of polyethylene, polystyrene, and PVC, respectively. In the realm of adhesives and coatings, organic peroxides are utilized to cure polyester and vinyl ester resins. They also find applications in the pharmaceutical and cosmetic industries, where they are used in the synthesis of certain compounds and as active ingredients in acne treatments, respectively.

Examples

Some common examples of organic peroxides include:

• Benzoyl peroxide: Widely used in the treatment of acne as well as in the polymer industry as a curing agent.
• Dicumyl peroxide: Employed in the vulcanization of rubber and as a polymerization initiator.
• Methyl ethyl ketone peroxide: A catalyst in the curing of polyester resins used in fiberglass and as a hardener in the production of composite materials.

Regulation

The handling, storage, and transportation of organic peroxides are subject to stringent regulations due to their potential hazards. In the United States, the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA) have established specific guidelines and regulations to ensure the safe management of these chemicals. Internationally, the United Nations has classified organic peroxides as a distinct hazard class for the purposes of transportation and shipping.

See Also

• Free radical
• Polymerization
• Explosive material
• Chemical hazard