Question

Aniline does not undergo Friedel-Crafts reaction. Why?

Hint:

- AlCl\(_3\) forms a salt with aniline, deactivating the benzene ring. - Electrophilic substitution is hindered, preventing Friedel-Crafts reaction.

Answer 1

Due to salt formation with AlCl\(_3\), aniline becomes a Lewis base, deactivating the benzene ring.
Step 1: Role of Lewis Acid Catalyst in Friedel-Crafts Reaction - Friedel-Crafts alkylation and acylation require a Lewis acid catalyst like AlCl\(_3\) to generate the electrophile. 

Step 2: Interaction Between Aniline and AlCl\(_3\) - Aniline (\( \text{C}_6\text{H}_5\text{NH}_2 \)) has a lone pair on nitrogen, which interacts with AlCl\(_3\), forming a salt. \[ \text{C}_6\text{H}_5\text{NH}_2 + AlCl_3 \rightarrow [\text{C}_6\text{H}_5\text{NH}_2]^+ [AlCl_3]^- \] - This deactivates the benzene ring, making it less reactive toward electrophilic substitution. 

Step 3: Conclusion Due to this salt formation, aniline does not undergo Friedel-Crafts reaction.