Preparation of Acetanilide

Acetanilide is a white organic solid compound used primarily in organic synthesis. N-phenylacetamide, acetanilide and acetanil are other names of this compound. It was used in the past to treat fever and headache and was known as Antifebrin by its brand name.

Aim:

To prepare the organic compound acetanilide from aniline, glacial acetic acid/acetic anhydride and zinc dust.

Theory:

Acetanilide is prepared from aniline when it reacts with acetic anhydride/glacial acetic acid in the presence of zinc dust. A mixture of aniline, glacial acetic acid, acetic anhydride and zinc dust is refluxed under anhydrous condition and then poured the mixture into ice cold water to get acetic anhydride precipitate. The crude precipitate of acetic anhydride is recrystallized to get pure crystals of acetanilide.

The chemical reaction is given below.

Preparation of Acetanilide

Zinc is used to prevent the oxidation of aniline during the chemical reaction. Acetanilide is medicinally important and it is used as febrifuge.

Acetanilide cal also be prepared by acetylating aniline with acetic anhydride in the presence of concentrated hydrochloric acid. Dissolve aniline in hydrochloric acid and add acetic anhydride stir well. Pour the mixture to sodium acetate in water. Acetanilide is formed which can be separated and recrystallised by ethyl alcohol.

Other names – N-phenylacetamide, N-phenylethanamide, Acetanil

Materials Required:

  1. Aniline
  2. Glacial acetic acid
  3. Acetic anhydride
  4. Zinc dust
  5. Distilled water
  6. Round bottom flask
  7. Beaker
  8. Pipette
  9. Reflux condenser
  10. Funnel
  11. Stirrer
  12. Bunsensurner
  13. Filter paper
  14. Electronic balance

Apparatus Setup:

Lab Preparation of Acetanilide

Procedure:

  1. Wash all the apparatus with distilled water before starting the experiment.
  2. Take a round bottom flask in that add 10ml of aniline and 20ml of acetic anhydride and glacial acetic acid mixture and add zinc dust.
  3. Fix the reflux condenser with the round bottom flask.
  4. Heat the mixture gently for about 15-20 minutes on oil bath.
  5. Pour the hot mixture in a beaker containing ice cold water with constant stirring.
  6. Stir the mixture vigorously to hydrolyse excess of acetic anhydride.
  7. Once all the acetanilide is precipitated collect and filter in buchner funnel.
  8. The precipitate obtained is a crude sample of acetanilide. To get the pure crystals crystallization should be carried out.

Crystallization:

Transfer the crude sample into a beaker containing 20ml water and heat gently. If the solution is coloured then add a small amount of activated carbon. Filter the hot solution with a funnel. Cool the mixture for 30 min so that white shiny crystals of acetanilide separates out. Filter off the crystals, wash them with water and dry in the foldes of filter paper.

Observations:

Colour of the crystals

Colourless crystals

Shape of the crystals

Plate shaped

Melting point

114oC

Results and Discussion:

The yield of Acetanilide is ______gm.

Precautions:

  1. Do not inhale the fumes of acetic anhydride.
  2. Always carry out experiments in fuming chamber or near the window.
  3. Use the water condenser for refluxing the reaction mixture.
  4. Dry the crystals of acetanilide before finding the weight and its melting point

Viva Questions:

1. Name any two acetylating agent?
Ans: Acetic anhydride and acetyl chloride are the two acetylating agents.

2. What is the need to add zinc during the preparation of acetanilide?
Ans: Zinc is added to prevent the oxidation of aniline during the reaction. It reduces the coloured impurities present in the solution.

3. What is nitrating mixture?
Ans: The mixture of concentrated acids like nitric acid and sulfuric acid is called nitrating mixture.

4. What is the IUPAC name for acetanilide?
Ans: The IUPAC name for acetanilide is N-phenylacetamide

5. Mention any two uses of acetanilide.
Ans: Acetanilide is used in the synthesis of penicillin and in other pharmaceuticals. It is also used as an antipyretic agent menas fever reducing agent.

 

Keep visiting Byjus to learn more about class 12 CBSE chemistry practicals.

2 Comments

  1. How is zn metal form complex in this reaction?

    1. In the formation of Acetanilide zinc prevent the oxidation of aniline during the reaction. It reduces the coloured impurities present in the solution. It does not form any complex compound.

Leave a Comment

Your email address will not be published. Required fields are marked *