why benzoic acid does not undergo friedal craft reaction?

Hi,

Friedal craft reaction involves the attack by an electrophile to the substituted benzene ring.

Benzoic acid does not undergo Friedel Crafts reaction because the carboxyl group is strongly deactivating and the catalyst anhydrous aluminium chloride used in the reaction acts as Lewis acid and gets bonded to carboxyl group.

Hope it is clear to you.

Best Wishes!