PREPARATION OF ACETYL SALICYLIC ACID

OBSERVATION AND CALCULATIONS:-

Molecular weight of 2-Amino-benzoic acid = 137.0g

Molecular weight of Acetyl salicylic acid = 180.0g

137.0g of 2-amino benzoic acid yields acetyl salicylic acid = 180.0g

1.0g of 2-amino benzoic acid yields acetyl salicylic acid = 180/137g

6.9g of 2-amino benzoic acid yields acetyl salicylic acid = 180/137 ´ 6.9

= 9.06g

Theoretical yield = 9.06g

Practical yield = 7.92g

Percentage yield = Practical yield/Theoretical yield ´ 100

= 7.92/9.06 ´ 100

= 87.4%

RESULT:- Percentage yield of acetyl salicylic acid is 87.4%.

APPARATUS:- Round bottom flask, Burner, Stand, Beaker, Funnel, Condenser, Water bath, stirrer etc.

CHEMICALS:-

Sodium nitrite

2-Amino benzoic acid

PROCEDURE:-

1. 6.0g of sodium nitrite was mixed with 20.0ml of water and placed in ice (solution No. 1).

2. 6.9g of 2-Amino benzoic acid was mixed with 100.0ml of ice cold 70% HCl (solution No. 2).

3. Solution No. 1 was added to solution No. 2, gradually by constant stirring (temperature should be less than 5^oC).

4. The mixture was allowed to remain in the ice for 15 minutes. Copper turnings were then added.

5. The solution was then heated in a water bath for 20 minutes at temperature not more than 50⁰C.

6. Precipitates of salicylic acid were formed. These were filtered, dried and added to 30.0ml of acetylating mixture (15.0ml of glacial acetic acid & 15.0ml of acetyl chloride).

7. Reflux condensation was carried out for 30 minutes.

8. The condenser was removed and the reaction mixture was transferred to 50.0ml of ice-cold water.

9. Precipitates of acetyl salicylic acid were obtained, which were filtered and dried.

10. Precipitates were weighed and percentage yield was calculated.