Aspirin Synthesis

Chemical synthesis of aspirin

Aspirin, also known as acetylsalicylic acid, can be synthesized through a process called esterification. Here are the steps for the chemical synthesis of aspirin:

Materials needed:

  • Salicylic acid (2-hydroxybenzoic acid)
  • Acetic anhydride
  • Sulfuric acid
  • Water
  • Sodium bicarbonate
  • Ice


  1. In a flask, mix 10 g of salicylic acid with 20 mL of acetic anhydride.
  2. Add 5 drops of concentrated sulfuric acid to the mixture as a catalyst.
  3. Heat the mixture gently on a water bath for about 15 minutes. The mixture will turn into a clear, colorless liquid.
  4. Remove the flask from the water bath and let it cool to room temperature.
  5. Add 20 mL of water to the flask to dissolve any remaining salicylic acid.
  6. Slowly add sodium bicarbonate to the mixture until the fizzing stops. This will neutralize the excess acetic acid.
  7. Cool the mixture in an ice bath until crystals form.
  8. Filter the crystals using a Buchner funnel and wash them with a small amount of cold water.
  9. Dry the crystals in a desiccator or on filter paper.
  10. Weigh the dried crystals to determine the yield of aspirin.

The chemical reaction involved in the synthesis of aspirin is:

salicylic acid + acetic anhydride → aspirin + acetic acid

This reaction is an example of esterification, which involves the formation of an ester by reacting a carboxylic acid with an alcohol in the presence of an acid catalyst. In this case, salicylic acid acts as the carboxylic acid, and acetic anhydride acts as the alcohol. The sulfuric acid catalyst helps to speed up the reaction.