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 out one of the hydrogens on benzene with one of these halogens here. If this is Br2, then this has to be FeBr3. If this is Cl2, then this has to be FeCl3. At the end, the H is substituted out, the halogen comes in.
Next, we have Friedel-Crafts alkylation. Here we use as our reagent an alkyl halide. 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 bromide. 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 an alkyl group.