Bromine complex compounds cations, with pyridine

The intermediate in both reactions is a cation but the first (from cyclohexene) adds an anion while the second (from benzene) loses a proton so that the aromatic system can be restored. Notice also that neutral bromine reacts with the alkene but the cationic AICI3 complex is needed for benzene. Another way to produce a more electrophilic source of bromine is to use a pyridine catalyst. Pyridine attacks the bromine molecule producing a cationic bromine compound. 

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