Question

Show how to convert substances like Benzene to Aniline or Phthalimide to N-alkyl phthalimide.

Hint:

Benzene → Aniline requires nitration followed by reduction, while phthalimide alkylation is a key step in Gabriel synthesis.

Answer 1

Step 1: Conversion of Benzene to Aniline.
The conversion of benzene to aniline takes place in two main steps: nitration followed by reduction.

(i) Nitration of Benzene:
Benzene reacts with concentrated nitric acid in the presence of concentrated sulfuric acid to form nitrobenzene.

C₆H₆ + HNO₃ → C₆H₅NO₂ + H₂O
(conc. H₂SO₄)

(ii) Reduction of Nitrobenzene:
Nitrobenzene is reduced using Sn/HCl, Fe/HCl, or catalytic hydrogenation to form aniline.

C₆H₅NO₂ + 3H₂ → C₆H₅NH₂ + 2H₂O
(or Sn/HCl followed by NaOH)

Thus, benzene is converted into aniline through nitration and subsequent reduction.

Step 2: Conversion of Phthalimide to N-alkyl Phthalimide.
This conversion occurs via the Gabriel phthalimide synthesis method.

(i) Formation of Potassium Phthalimide:
Phthalimide reacts with alcoholic KOH to form potassium phthalimide.

Phthalimide + KOH → Potassium phthalimide + H₂O

(ii) Alkylation Reaction:
Potassium phthalimide reacts with an alkyl halide (R–X) to form N-alkyl phthalimide.

Potassium phthalimide + R–X → N-alkyl phthalimide + KX

This reaction involves nucleophilic substitution (S_N2 mechanism), where the nitrogen atom attacks the alkyl halide.

Conclusion.
Benzene is converted into aniline through nitration and reduction reactions, while phthalimide forms N-alkyl phthalimide via alkylation in the Gabriel synthesis method. These transformations are important in the preparation of aromatic amines and substituted amine derivatives.