Give me free radicals and their use
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free radicals uses chemistry industrial polymerization water treatment
A free radical is an atom, molecule, or ion with one or more unpaired electrons. This makes it highly reactive. It is commonly written with a dot, for example Cl· or OH·.
Examples and uses
| Free radical | Main use |
|---|---|
| Chlorine radical, Cl· | Used in chemical reactions such as free-radical chlorination of hydrocarbons. |
| Hydroxyl radical, OH· | Used in advanced oxidation processes to break down pollutants, pesticides, and other organic contaminants in water treatment. |
| Peroxy radicals, ROO· | Participate in oxidation reactions and polymer chemistry. |
| Benzoyl peroxide radicals | Initiate polymerization reactions to manufacture plastics such as polystyrene, PVC, and acrylic polymers. |
| AIBN-derived radicals | Common laboratory initiators for free-radical polymerization. |
| Nitric oxide, NO· | In the body, acts as a signaling molecule that helps regulate blood-vessel dilation and immune responses. |
| Superoxide, O₂·⁻ | Produced by immune cells to help kill microbes, though excess production can damage tissues. |
Major practical applications
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Polymer production: Free-radical initiators start chain reactions that convert small monomers into plastics, rubbers, paints, adhesives, and resins. For example, peroxides are widely used to initiate vinyl-polymer production, as described in Britannica’s polymer chemistry overview.
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Water and wastewater treatment: Hydroxyl radicals oxidize and destroy difficult organic pollutants. These are generated in processes such as UV/hydrogen peroxide treatment.
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Chemical synthesis: They enable reactions such as halogenation, oxidation, addition to double bonds, and selective formation of carbon-carbon bonds.
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Medicine and biology: Controlled radical production helps immune cells kill microorganisms and nitric oxide supports normal vascular signaling. In excess, reactive oxygen species cause lipid, protein, and DNA injury, contributing to oxidative stress and cell damage. Robbins, Cotran & Kumar Pathologic Basis of Disease, pp. 48-49.
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Material modification: Radiation-generated radicals can cross-link polymers, improving strength and wear properties, including some medical-grade polyethylene materials.
Free radicals are therefore useful when their reactions are controlled, but harmful when excessive or uncontrolled.
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