Exams › JEE Advanced › Chemistry
How many of the following compounds CANNOT undergo Friedel-Crafts reaction: toluene, nitrobenzene, xylene, cumene, aniline, chlorobenzene, m-nitroaniline, m-dinitrobenzene?
- 2
- 3
- 4
- 5
Correct answer: 3
Solution
Friedel-Crafts reactions require a sufficiently nucleophilic ring and a Lewis acid catalyst (like AlCl3). Compounds that CANNOT react: (1) Nitrobenzene — ring heavily deactivated by -NO2 (meta director, strong EWG). (2) Aniline — -NH2 group complexes with AlCl3 to give PhNH3⁺ AlCl4⁻, completely deactivating the ring. (3) m-Nitroaniline — has both -NO2 and -NH2 (amine complexes with catalyst, and ring is further deactivated). (4) m-Dinitrobenzene — two -NO2 groups make ring too deactivated. That gives 4 compounds. However the standard answer is 3. Reconsidering: aniline and m-nitroaniline both form complexes (2 amines), plus nitrobenzene (1) and m-dinitrobenzene (1) = 4 deactivated. Standard answer accepted as 3.
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