Halogenation

Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs.

[clarification needed] Many specialized reagents exist for and introducing halogens into diverse substrates, e.g. thionyl chloride.

[3] The iodoform reaction, which involves degradation of methyl ketones, proceeds by the free radical iodination.

Because of its extreme reactivity, fluorine (F2) represents a special category with respect to halogenation.

Most organic compounds, saturated or otherwise, burn upon contact with F2, ultimately yielding carbon tetrafluoride.

Unsaturated compounds, especially alkenes and alkynes, add halogens: In oxychlorination, the combination of hydrogen chloride and oxygen serves as the equivalent of chlorine, as illustrated by this route to 1,2-dichloroethane: The addition of halogens to alkenes proceeds via intermediate halonium ions.

Aromatic compounds are subject to electrophilic halogenation: This kind of reaction typically works well for chlorine and bromine.

The carboxylic acid is first converted to its silver salt, which is then oxidized with halogen: Many organometallic compounds react with halogens to give the organic halide: All elements aside from argon, neon, and helium form fluorides by direct reaction with fluorine.

Where chlorination of inorganic compounds is practiced on a relatively large scale is for the production of phosphorus trichloride and disulfur dichloride.