The bromination is a special case of the halogenation, and refers to a chemical reaction to introduce one or more bromine atoms in an organic compound . This can be an addition or a substitution reaction . The reaction mechanism can be ionic or radical .
Numerous compounds are possible as substrates for a bromination:
- Alkanes ( radical substitution )
- Alkenes (ionic electrophilic addition and bromination in the allyl position)
- Alkynes (ionic electrophilic addition)
- Aromatics (ionic electrophilic substitution and bromination in the benzyl position)
In the chemical industry, chlorination is often used as an alternative , since chlorine is cheaper and has a lower molar mass . In the laboratory, on the other hand, bromination is usually preferred because bromine is easier to handle ( liquid at room temperature) and has greater selectivity due to its lower reactivity .
Bromination of alkanes
Bromination of alkenes / alkynes
The electrophilic bromination of alkenes / alkynes takes place at the double / triple bond and can also be carried out with complex substrates with several functional groups. The addition of bromine to alkenes / alkynes proceeds with high atom economy .
Bromination of aromatics
The bromination on the nucleus is an example of electrophilic substitution .
Bromination in the allyl or benzyl position
A special feature is the introduction of a bromine atom in the allylic or benzylic position. The bromination at this point is also known as the Wohl-Ziegler reaction . This is a radical substitution in which NBS ( N -bromosuccinimide ) is used as the reagent in order to keep the bromine concentration low and thus suppress electrophilic addition to the double bond or the aromatic.
- Ivan Ernest: Binding, Structure and Reaction Mechanisms in Organic Chemistry , Springer-Verlag, 1972, pp. 297–306, ISBN 3-211-81060-9 .