So here we have a summary of our benzene reactions. We have halogenation in it. We have the reagent of X2 which could represent BR2 or CL2. We use our catalyst to get things going. In essence what happens is that we substitute at one of the hydrogens on benzene with one of these halogens.
Here if this is BR2 then this has to be Fe BR3 if this is CL2 and this has to be Fe CL3. At the end the H is substituted out. The halogen comes in next. We have Friedel–Crafts Alkylations here we use as an our reagent and alkyl Halid X again could be CL or BR. But now we're using the catalyst of aluminum and it could be either aluminum chloride or aluminum bromide.
Here we substitute out our hydrogen and bring in our alkyl group here. If the X is CL, then this is aluminum chloride. If the X here is bromine, then this is aluminum bromine. So remember both of these reactions are quite similar. They use similar types of catalysts and they're just substituting out an H. This one substitutes in a halogen, this one here in alkyl group.