Laboratory preparation of aniline

Aniline was first prepared by Unverdorben (1826) by dry distillation of indigo. In the laboratory, it can be prepared by the reduction of nitrobenzene with tin and hydrochloric acid.

Sn,HCl

C₆H₅NO₂ + 6H ——————→ C₆H₅NH₂ + 2H₂O

Aniline produced combines with H₂SnCl₆ (SnCl₄ + 2HCl) to form a double salt.

2C₆H₅NH₂ + SnCl₄ + 2HCl —→ (C₆H₅NH₃)₂ SnCl₆

^{Double salt}

From double salt, aniline is obtained by treating with conc. caustic soda solution.

(C₆H₅NH₃)₂SnCl₆ + 8NaOH —→ 2C₆H₅NH₂ + 6NaCl + Na₂SnO₃ + 5H₂O

On a commercial scale, aniline is obtained by reducing nitrobenzene with iron filings and hydrochloric acid.

Aniline is also obtained on a large scale by the action of amine on chlorobenzene at 200°C under 300-400 atm pressure in presence of cuprous catalyst.

200^oC

2C₆H₅ + 2NH₃ + Cu₂O ———————→ 2C₆H₅NH₂ + Cu₂Cl₂ + H₂O