Halogenation

Overview

Halogenation is a chemical reaction that incorporates a halogen atom into a molecule. More specific descriptions exist that specify the type of halogen: fluorination, chlorination, bromination, and iodination.

In a Markovnikov addition reaction, a halogen like bromine is reacted with an alkene which causes the π-bond to break forming an haloalkane. This makes the hydrocarbon more reactive and bromine as it turns out, is a good leaving group in further chemical reactions such as nucleophilic aliphatic substitution reactions and elimination reactions

Several main types of halogenation exist, including:

• Free radical halogenation
• Ketone halogenation
• Electrophilic halogenation
• Halogen addition reaction

Specific halogenation methods are the Hunsdiecker reaction (from carboxylic acids) and the Sandmeyer reaction (arylhalides).

An example of halogenation can be found in the organic synthesis of the anesthetic halothane from trichloroethylene which involves a high temperature bromination in the second step :

Halothane synthesis

Halothane synthesis

See also

• Haloalkane (Alkyl halide)
• Halogenoarene (Aryl halide)
• Haloketone
• Electrophilic substitution