Question

Give reasons for the following:
Benzoic acid does not undergo Friedel-Crafts reaction.

Hint:

Always check if a substituent withdraws electrons — deactivation blocks substitution!

Answer 1

Benzoic acid features a carboxyl (–COOH) group bonded to a benzene ring. This –COOH group exerts a strong electron-withdrawing influence through both its mesomeric (–M) and inductive (–I) effects. Consequently, it deactivates the benzene ring toward electrophilic substitution reactions, such as Friedel-Crafts alkylation or acylation. Furthermore, the –COOH group can complex with Lewis acid catalysts (e.g., AlCl$_3$), diminishing the catalyst's capacity to generate the electrophile. Thus, benzoic acid does not participate in Friedel-Crafts reactions.