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Subject - Organic Chemistry
Halogenation is a chemical reaction that incorporates halogen atoms into an organic molecule or that transforms an element into a halogen.
The most important reactions for the incorporation of halogen atoms into organic compounds are additions and substitutions. Unsaturated molecules can add halogens or hydrogen halides.
Hydrogen atoms can be substituted with fluorine, chlorine or bromine by using radical reactions, for example by photodissociation of chlorine or bromine to generate halogen atoms. In aliphatic chains, functional groups, such as OH, can be substituted with a halide (nucleophilic substitution). Decomposition of phenyldiazonium halides with loss of nitrogen allows for the introduction of any halogen into benzene rings. Chlorine and bromine can also be introduced into benzene rings by using ferric chloride as catalyst (electrophilic aromatic substitution). Using electrofluorination (anodic fluorination in anhydrous hydrofluoric acid), perfluorinations (exchange of all hydrogen atoms with fluorine) are possible.
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