Radical (chemistry)

Radical (chemistry)

A radical in chemistry is an atom, molecule, or ion that has unpaired valence electrons. With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spontaneously dimerize. Most organic radicals have short lifetimes.

A notable example of a radical is the hydroxyl radical (HO•), a molecule that has one unpaired electron on the oxygen atom. Two other examples are triplet oxygen and benzyl radical.

Formation and occurrence of radicals

Radicals can be formed by ionizing radiation, heat, electrical discharge, or photochemical reactions. Certain radicals are used in radical polymerization and radical chain reactions, which are essential to many processes in chemistry, biochemistry, and medicine.

Reactivity and applications of radicals

Radicals play key roles in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, and many other chemical processes, including human physiology. For example, in living organisms, radicals are involved in cell damage and cancer.

See also

• Radical
• Radical polymerization
• Radical chain reaction
• Hydroxyl radical
• Triplet oxygen
• Benzyl radical