We know that AlCl3 is a lewis acid. It can give Friedel Crafts reactions. Here, we can see that AlCl3 acts as a lewis acid and accepts the electron pair from the chlorine atom. This forms−AlCl4. Alongside this, a carbocation is also formed.
Now, this carbocation is an electrophilic carbon. So, benzene rings can give electrophilic substitution reactions here. So, as a result, the double bond of benzene will attack on the carbocation and a C-C bond will be formed there. Then after losing a proton, the carbon ring becomes aromatic. This, we obtain a compound which has two ring structures. One ring is aromatic and the other is not aromatic.
Friedel-Craft alkylation takes place to give a six membered ring.





