Question

Describe the laboratory method to prepare aniline and write the related chemical equation. Write also the equations of its two chemical properties and uses.

Hint:

In lab preparation, Sn/HCl reduces nitrobenzene effectively. Always neutralise with alkali to free the amine. Aniline is highly reactive in electrophilic substitution due to the strong +M effect of –NH$_2$.

Answer 1

Preparation of Aniline:
- Aniline (\(\mathrm{C_6H_5NH_2}\)) is prepared in the laboratory by the reduction of nitrobenzene.
- Nitrobenzene is reduced using tin (Sn) and concentrated HCl, followed by neutralisation with NaOH.
\[ \mathrm{C_6H_5NO_2 + 6[H] \xrightarrow{Sn/HCl} C_6H_5NH_2 + 2H_2O} \] Two Chemical Properties:
(i) Bromination:
Aniline reacts with bromine water to give 2,4,6-tribromoaniline (a white precipitate).
\[ \mathrm{C_6H_5NH_2 + 3Br_2(aq) \;\longrightarrow\; 2,4,6\!-\!C_6H_2Br_3NH_2 + 3HBr} \] (ii) Acetylation:
Aniline reacts with acetic anhydride to form acetanilide.
\[ \mathrm{C_6H_5NH_2 + (CH_3CO)_2O \;\longrightarrow\; C_6H_5NHCOCH_3 + CH_3COOH} \] Uses of Aniline:
1. Used in the manufacture of dyes such as aniline yellow, methyl orange.
2. Important raw material for drugs, rubber processing chemicals, and polymers.
3. Used for the preparation of paracetamol (acetaminophen).
Thus, aniline is prepared by reduction of nitrobenzene, shows EAS and acylation, and has wide industrial uses.