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Engineering Chemistry Lab Experiments

To prepare Aspirin from salicylic acid


To prepare Aspirin from salicylic acid.

Apparatus Required:

Conical flask, Beakers, glass rod, funnel etc

Chemicals Required :

  1. Salicylic acid - 2.5gm (MW= 138)
  2. Acetic anhydride - 3.5ml
  3. Con.H2SO4 - 3 to 4 drops

Principle :

Salicylic acid is a phenolic acid. The phenolic group can be easily acetylated using acetic anhydride. This is an example of Nucleophilic substitution reaction. Phenolic hydroxyl group of salicylic acid acts as a Nucleophile and lone pair of electrons on the Oxygen atom attacks the carbonyl group of acetic anhydride to form Aspirin.

prepare Aspirin from salicylic acid


Take all the three chemical compounds in a given 250ml conical flask. Shake the mixture thoroughly and warm the reaction mixture at 50-60oC for 15 min. on a water bath with continuous stirring with glass rod and allow the reaction mixture to cool. Add nearly 100ml of distilled water. Stir thoroughly and filter the product.


Dissolve the product in 20ml alcohol and pour the solution into warm water, If solids separate warm it to dissolve the solids and clear the solution and allow it to cool slowly to get beautiful needles of Aspirin(MW=180) is formed.


Percentage yield of product ______%

Viva Questions

1) Define Nucleophilic substitution reaction?

2) What is molecular weight of aspirin?

3) What is the another name of aspirin?

4) What are applications of aspirin?

5) Write the chemical equation for synthesis of aspirin?