Organic conversion

Benzoic acid to aniline

2 steps: condensation, then Hoffmann bromamide degradation

Class 12, Chapter 8 Aldehydes, Ketones and Carboxylic Acids; Class 12, Chapter 9 Amines

Benzoic acidC₆H₅COOHCarboxylic acid
Step 1
NH₃, then heat
i
The acid first forms the ammonium salt, which loses water on heating.
BenzamideC₆H₅CONH₂Amide
Step 2
Br₂ + NaOH(aq)
Hoffmann bromamide degradation
i
Hoffmann bromamide degradation removes the carbonyl carbon (benzamide, 7 C, gives aniline, 6 C).
AnilineC₆H₅NH₂Amine

Alternative routes (2)

Benzoic acid → Benzoyl chloride → Benzamide → Aniline
1. Benzoic acid to benzoyl chloride: SOCl₂.
2. Benzoyl chloride to benzamide: NH₃.
3. Benzamide to aniline: Br₂ + NaOH(aq).
Benzoic acid → Sodium benzoate → Benzene → Nitrobenzene → Aniline
1. Benzoic acid to sodium benzoate: NaOH.
2. Sodium benzoate to benzene: NaOH + CaO (soda lime), heat.
3. Benzene to nitrobenzene: conc. HNO₃ + conc. H₂SO₄, 323 to 333 K.
4. Nitrobenzene to aniline: Sn + conc. HCl.

Why these reagents

Reagent and reason, step by step

Step 1: Benzoic acid to benzamide: NH₃, then heat The acid first forms the ammonium salt, which loses water on heating.
Step 2: Benzamide to aniline: Br₂ + NaOH(aq) Hoffmann bromamide degradation removes the carbonyl carbon (benzamide, 7 C, gives aniline, 6 C).

Questions

How many steps does it take to convert benzoic acid to aniline?

2 steps: Benzoic acid, then benzamide, then aniline.

Which named reaction is used to convert benzoic acid to aniline?

Hoffmann bromamide degradation. An amide treated with bromine and aqueous or alcoholic NaOH gives a primary amine with one carbon atom fewer.

What is the reagent for step 1 of benzoic acid to aniline?

Benzoic acid to benzamide: NH₃, then heat. The acid first forms the ammonium salt, which loses water on heating.