The preparation of Benzoic acid from benzamide

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EXPERIMENT ( 4 )        

Topic :        The preparation of Benzoic acid from benzamide

Introduction :        The preparation of benzoic acid from benzamide is a hydrolysis.

                        In this experiment, you are requested to prepare and purify benzoic acid by some techniques.

Chemicals :        Benzamide, Dilute NaOH, Dilute HCl

Procedures :        1.        Weigh out 3 g of benzamide. Place it in a 100 cm3 (or larger) conical flask and add to it 50 cm3 of

                                dilute sodium hydroxide solution.

  1. Fit the flask with a cork carrying a glass tubing and boil the mixture for about 15 minutes.

Test the gas evolved at the open end of the glass tubing when the mixture begins to boil.

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  1. Allow the reaction mixture to cool and then transfer it to a 250 cm3 beaker.  Add an excess of

dilute HCl with a dropper, swirling continuously until a copious amount precipitate is obtained.

  1. Filter the resulting solution under suction, wash the crystals thoroughly with a minimum amount of

ice cold water.

  1. Recrystallise the crude solid from boiling water, filter to obtain pure crystals of the product.
  2. Dry these crystals thoroughly between filter paper until no further sign of dampness is seen on the paper. Inspect the shape of the crystals using a hand lens. Measure ...

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