Wohl–Ziegler bromination

The Wohl–Ziegler reaction
is a <a href="/facts/Chemical_reaction/GpqWlKrz">chemical reaction</a> that involves the <a href="/facts/Allylic/CDxPwyvF">allylic</a> or <a href="/facts/Benzylic/kHmqYwqH">benzylic</a> <a href="/facts/Bromination/vYrGVWcJ">bromination</a> of <a href="/facts/Hydrocarbon/Dcg95Ju5">hydrocarbons</a> using an <a href="/facts/N-Bromosuccinimide/kcW9F19d">N-bromosuccinimide</a> and a <a href="/facts/Radical_initiator/8XlX2G67">radical initiator</a>.

Best yields are achieved with <a href="/facts/N-Bromosuccinimide/kcW9F19d">N-bromosuccinimide</a> in <a href="/facts/Carbon_tetrachloride/S2ekjT0E">carbon tetrachloride</a> solvent. Several reviews have been published.
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 <a href="/facts/Succinimide/v3eRV6hY">succinimide</a> (which floats on top) the reaction has finished. Due to the high toxicity and ozone-depleting nature of carbon tetrachloride, <a href="/facts/Trifluorotoluene/KeStvU8g">trifluorotoluene</a> has been proposed as an alternative solvent suitable for the Wohl–Ziegler bromination.
The corresponding chlorination reaction cannot generally be achieved with N-chlorosuccinimide, although more specialized reagents have been developed, and the reaction can be achieved industrially with chlorine gas.

Wohl–Ziegler bromination open-in-new

Wohl–Ziegler bromination