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CH1012
SPARES III
2) The bromination of benzene requires
the presence of FeBr3 as well as Br2. 
What is the function of the FeBr3?
2) The benzene ring is quite stable & unreactive towards addition.  The use of
FeBr3 as a Lewis acid catalyst results in the
formation of Br+ which is active towards
substitution of the ring.