55. ASPIRIN

Aspirin

Formula: C9H8O4

Other Names: Acetyl salicylic acid, 2-acetoxy-benzoic acid

Preparation

Aspirin is prepared by reacting salicylic acid with an excess amount of acetic anhydride. A small quantity of strong acid is used as a catalyst to speed up the reaction.

Test for Purity

  • Appearance: A 10% solution in ethanol should appear clear.
  • Heavy metals: < 10 ppm
  • Arsenic: < 2 ppm
  • Chlorides: < 430 ppm
  • Sulfates: < 600 ppm
  • Sulfated ash: < 0.1%
  • Loss on drying: < 0.5%
  • Salicylic acid: < 0.01%

Assay

Aspirin can be assayed by:

  • Hydrolysis method: Hydrolyze aspirin using a measured volume of N/2 NaOH. Titrate the excess alkali using N/2 acid. The final neutralized solution contains sodium acetate and monosodium salicylate.
  • Acid-base titration:
    • Use ethanol as a co-solvent.
    • 1 ml of 0.5 M NaOH corresponds to 0.04504 g of aspirin.

Uses

  • Reduces fever and relieves mild to moderate pain such as headache, muscle pain, toothache, and common cold.
  • Helpful in reducing pain and swelling in arthritis.
  • Acts as a non-steroidal anti-inflammatory drug (NSAID) and belongs to the salicylate class.

Detailed Notes:

For PDF style full-color notes, open the complete study material below:

PATH: PHARMD/PHARMD NOTES/ PHARMD FIRST YEAR NOTES/ ORGANIC CHEMISTRY/ PHARMACEUTICAL ORGANIC CHEMISTRY/ ASPIRIN.

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