BACKGROUND
The freshly redistilled aniline, is almost a colourless oily liquid which being practically insoluble in water. Therefore, before carrying out the ‘acetylation’ aniline has got to be made soluble in the aqueous medium. It can be accomplished by adding requisite amount of concentrated HCl whereby the highly reactive amino function easily takes up a proton from the dissociation of HCl in water, get protonated to yield aniline hydrochloride that is water-soluble.
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Subsequently, the soluble form of aniline is reacted with acetic anhydride in the presence of sodium acetate. The acetate ion obtained from the hydrolysis of the salt (sodium acetate) helps to sustain the acetylation reaction in the forward direction to yield acetanilide completely.1
REQUIREMENTS
Chemical: Aniline – 10 ml,
Acetic anhydride – 13 ml,
Sodium acetate – 16.5 g
Conc. HCL – 9 ml.
PROCEDURE
Transfer 10 ml aniline in to a 500 ml beaker, add 9 ml concentrated hydrochloric acid and 25 ml distilled water into it. Stir the contents of the beaker thoroughly with a glass rod till the whole of aniline undergoes dissolution. Dissolve 16.5 g sodium acetate in 50 ml distilled water in a separate beaker.
To the clear solution of aniline, add 13 ml of acetic anhydride, in small lots at intervals, with constant vigorous stirring until a perfect homogeneous solution is obtained. Immediately pour the solution obtained into the sodium acetate solution. Stir the contents thoroughly and immerse the beaker containing the reactants in an ice-bath. Beautiful shining crystals of Acetanilide separate out.
Filter at the Buchner funnel by applying suction, wash with enough cold water, and squeeze out the excess of water by pressing with an inverted glass stopper. Transfer the crude product onto a watch glass with the aid of a stainless-steel spatula and finally dry it in an electric oven previously maintained at 80°C.
Calculation of Practical Yield: –
93 g of aniline on reacting with 102 g of acetic anhydride yields acetanilide = 135.16 g
10 g of aniline shall yield acetanilide = 135.16 / 93 × 10 = 14.5 g
Therefore, Theoretical yield of Acetanilide = 14.5 g
If reported Practical yield = 12 g
Then, Percentage Practical yield = Practical yield / Theoretical yield × 100
= 12 / 14.5 × 100 = 82.75 %
CONCLUSION
The yield of crude acetanilide (mp 113– 114°C) is approximately 12 g.
REFERENCES
- Kar A. Advanced Practical Medicinal Chemistry, New Age International (P) Limited Publication, New Delhi, Page No. – 71.
Also read:
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- Hydrolysis of Ethyl Acetate
- Synthesis of Dibenzal Acetone from Benzaldehyde by Claison Schmidt Reaction
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- Protein denaturation by egg albumin method (in vitro)
- Analgesic activity study of drugs by hot plate (Eddy’s hot plate) method
- Synthesis of Cinnamic Acid from Benzaldehyde
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