Question

Aniline does not undergo Friedel-Crafts reaction because 1.(A) It forms salt with the Lewis acid catalyst, AlCl₃.
2. (B) Nitrogen of aniline acquires negative charge.
3. (C) Nitrogen of aniline acquires positive charge.
4. (D) Nitrogen acts as a strong deactivating group in the further reaction.

• (A) It forms salt with the Lewis acid catalyst, AlCl3
• (B) Nitrogen of aniline acquires negative charge
• (C) Nitrogen of aniline acquires positive charge
• (D) Nitrogen acts as a strong deactivating group in the further reaction

Answer 1

The Correct Option is C

Aniline's inability to participate in the Friedel-Crafts reaction stems from the behavior of its nitrogen atom in the presence of a Lewis acid catalyst, such as AlCl₃. Typically, this reaction involves the formation of an electrophile from an alkyl or acyl halide reacting with a Lewis acid. However, in aniline, the nitrogen atom interferes with this process.

The reasons are as follows:

1. Aniline features an amino group (-NH₂), characterized by a lone pair of electrons on the nitrogen atom.

2. Upon exposure to a Lewis acid like AlCl₃, the nitrogen atom, due to its affinity for bond formation, donates its lone pair of electrons to the Lewis acid.

3. This electron donation results in a positive charge on the nitrogen atom, transforming the amino group into an electron-deficient center.

4. Consequently, the positively charged nitrogen destabilizes the aromatic ring, precluding the efficient formation of the carbocation intermediate essential for Friedel-Crafts alkylation or acylation reactions.

Therefore, the accurate explanation is: (C) Nitrogen of aniline acquires positive charge.