Hydrolysis of benzamide

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Chemistry Experiment 26

  1. Title:

Hydrolysis of benzamide

  1. Objective:

To prepare benzoic acid by means of hydrolysis of benzamide and calculate the percentage yield of this process.

  1. Theory:

Benzamide, like other amides, hydrolysis under acidic or alkaline conditions

Acid hydrolysis (not involved in this experiment)

(1)         + H2O     + NH3

Alkaline hydrolysis

(2)         + OH-     + NH4+

From (2), when H3O+ is further added, benzoic acid is formed

(3)+ H3O+

In reaction (2), the ammonium gas evolved is alkaline and can be tested by wet red litmus paper, it should turn from red to blue.

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On the other hand, in reaction (3), the HCl added should be in excess to ensure maximum benzoic acid formation. The sign of complete reaction can be told by testing it with wet blue litmus paper, it should turn from blue to red, indicating that the reaction mixture has become acidic.

Moreover, since benzoic acid has very low solubility in water, white precipitate would form which can be separated by simple filtration. Also a suction pump is connected below to speed up the filtration. The filtrate should then be washed to remove any impurities.

Lastly, by weighing ...

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