Aim:
To synthesize Benzanilide from Aniline by an acylation reaction
Reference:
F. G. Mann and B. C. Saunders, Practical Organic
Chemistry, 4th Ed, 1974, P. No. 245-246.
Requirement:
Apparatus:
Beaker, Stirrer, Filtration assembly, etc.
Chemicals:
Aniline,
Benzoyl chloride, 10% aqueous Sodium Hydroxide Solution.
Theory/Principle:
Insertion of benzoyl moiety instead of an active hydrogen
atom present in hydroxyl (OH), primary amino (NH) or secondary amino group (NH)
is usually termed as benzoylation reaction. The Process of
benzoylation of compounds containing active hydrogen such as phenol, Aniline,
Alcohol etc. with benzoyl chloride in the presence of aqueous NaOH is called Schotten
Baumann reaction. This particular reaction essentially bears a close resemblance to the phenomenon of acetylation except that in this specific instance
the reagent is (benzoyl chloride) which reacts in the presence of pyridine or 10% NaOH.
The amines are more soluble in acid chloride than in NaOH, the reaction occurs preferably
between benzoyl chloride and amine. In the preparation of benzanilide, NaOH
neutralizes the liberated HCl and also catalyze the reaction.
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| Fig. 1 Synthesis of Benzanilide from Aniline |
 |
| Fig. 2 Mechanism of Reaction |
Procedure:
- Add 1 ml (1.04 g.) of aniline to 15 ml. of 10% aqueous sodium hydroxide solution contained in a wide-necked bottle as before, and then add 1.5 ml. (1.7 g.) of benzoyl chloride, and shake vigorously for 15-20 minutes.
- The completion of the reaction is indicated by the disappearance of the pungent smell of benzoyl chloride
- The mixture becomes warm, and the crude benzoyl derivative separates as a white powder or if the shaking has not been sufficiently vigorous, as small pellets: when the reaction is complete.
- Filter off the product at the pump, break up any pellets with a spatula on the filter, and then thoroughly wash with water and drain.
- Benzanilide is thus obtained as colorless crystals, having m.p. 163°.
