Prepare benzamide from benzoinc acid.

1. Experiment No 4
Aim
To synthesize benzamide from benzoic acid and to determine its melting point.
References
1. Vogel’s Textbook of Practical Organic Chemistry, 5th Edition,
Longman Group Ltd., London, Page No. 1072–1073.
2. Furniss, Hannaford, Smith & Tatchell,
Vogel’s Textbook of Practical Organic Chemistry, 5th Edition,
Pearson Education, Page No. 1038–1039.
Theory
Benzamide is prepared by first converting benzoic acid into ammonium benzoate, which on
heating undergoes dehydration to form benzamide.
Reaction:
Benzoic acid + Ammonia → Ammonium benzoate
Ammonium benzoate —Δ→ Benzamide + Water
Requirements
• Benzoic acid – 5 g
• Liquor ammonia – excess
• Distilled water
• China dish
• Beaker
• Glass rod
• Bunsen burner / heating mantle
• Funnel
• Filter paper
Procedure
1. Take 5 g of benzoic acid in a beaker and add excess liquor ammonia slowly with
constant stirring until a clear solution is obtained.
2. Transfer the solution into a china dish.

2. 3. Evaporate the solution gently on a water bath to obtain ammonium benzoate.
4. Heat the dry ammonium benzoate carefully. It first melts and then solidifies forming
benzamide.
5. Allow the product to cool and dissolve it in hot water.
6. Filter if necessary and allow the filtrate to cool slowly to obtain benzamide crystals.
7. Filter, dry the crystals, and record the melting point.
Observation
• Appearance: White crystalline solid
• Yield: ~70–80%
• Melting point: 127–130°C
Result
Benzamide was successfully synthesized from benzoic acid. The melting point confirms the
purity of the compound.
Precautions
• Excess ammonia should be used for complete salt formation.
• Heating should be done gently to avoid charring.
• Use dry apparatus for better yield.
Conclusion
The synthesis of benzamide was carried out successfully by dehydration of ammonium
benzoate obtained from benzoic acid.