• Aspirin is a drug commonly used to treat pain and inflammation

Aspirin is synthesised as follows:

1. An esterification reaction occurs between salicylic acid (active ingredient) and ethanoic acid and/or ethanoic anhydride (derived from a reaction between two ethanoic acid molecule).
2. Product of the esterification reaction is acetylsalicylic acid, which is what we commonly call aspirin.
3. Acetylsalicylic acid once in the body is converted back into salicylic acid, which is the active ingredient that allows aspirin to reduce pain and inflammation.
4. See reaction diagram below – make sure that you know how aspirin is derived from salicylic acid.

The reason why acetylsalicylic acid is made is that it is less irritating to the stomach than salicylic acid. Originally, salicylic acid was used in its pure form, but that had side effects.