Functional Classes II, Reactions - Organic Chemistry Concepts: An EFL Approach - page 144

D
This gives a non-aromatic product of higher energy. It is better if the bromide ion acts
as a base in the deprotonation reaction to regenerate the delocalized aromatic system.
Try to draw this step.
E
Therefore the full sequence may be combined as follows.
If you refer to Program 22, you will see that this reaction is an electrophilic version of
the nucleophilic addition/elimination sequence which occurs with acyl derivatives.
Usually, because of the relatively low nucleophilic character of the aromatic nucleus,
the quality of the electrophile is often increased by a Lewis acid catalyst. For the above
bromination, this is done with FeBr 3 .
How might this Lewis acid activate the Br 2 ?
F
We can expect similar activation for chlorination (Cl 2 /FeCl 3 ), alkylation (RHal/AlHal 3 ),
and acylation (RCOHal/AlHal 3 ).
Draw the formation of these reactive species. Use examples of your choice for
alkylation and acylation.