Wohl–Ziegler bromination
From Wikipedia, the free encyclopedia
The Wohl–Ziegler reaction[1][2] is a chemical reaction that involves the allylic or benzylic bromination of hydrocarbons using an N-bromosuccinimide and a radical initiator.[3]
Wohl-Ziegler bromination | |
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Named after | Alfred Wohl Karl Ziegler |
Reaction type | Substitution reaction |
Identifiers | |
Organic Chemistry Portal | wohl-ziegler-reaction |
RSC ontology ID | RXNO:0000225 |
Best yields are achieved with N-bromosuccinimide in carbon tetrachloride solvent. Several reviews have been published.[4][5]
In a typical setup, a stoichiometric amount of N-bromosuccinimide solution and a small quantity of initiator are added to a solution of the substrate in CCl4, and the reaction mixture is stirred and heated to the boiling point. Initiation of the reaction is indicated by more vigorous boiling; sometimes the heat source may need to be removed. Once all N-bromosuccinimide (which is denser than the solvent) has been converted to succinimide (which floats on top) the reaction has finished. Due to the high toxicity and ozone-depleting nature of carbon tetrachloride, trifluorotoluene has been proposed as an alternative solvent suitable for the Wohl-Ziegler bromination.[6]
The corresponding chlorination reaction cannot generally be achieved with N-chlorosuccinimide,[7] although more specialized reagents have been developed,[8] and the reaction can be achieved industrially with chlorine gas.[9]