in chemistry, a molecule or atom that contains an unpaired electron but is neither positively nor negatively charged. Free radicals are usually highly reactive and unstable. They are produced by homolytic cleavage of a covalent bond (see chemical bond
); i.e., each of the atoms connected by the bond retains one of the two electrons making up the bond. The homolytic cleavage of a hydrogen molecule, H2
, produces two hydrogen free radicals (hydrogen atoms). Similarly, two chlorine free radicals can be produced from a chlorine molecule. Homolytic cleavage of the carbon-bromine bond in methyl bromide, CH3
Br, would produce a methyl free radical and a bromine free radical. The term free
is often dropped in referring to free radicals; this could lead to confusion if the term radical
were used synonymously with group
in organic chemistry, e.g., by calling an alkyl group an alkyl radical when free radical was not intended.
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