Acetylsalicylic acid (Aspirin)

What is Acetylsalicylic acid?

Acetylsalicylic acid is prototypical analgesic with a chemical formula C9H8O4.

It is also known as aspirin or 2-Acetoxybenzoic acid. It appears as a crystalline powder which is colourless to white in colour. Generally, it has no smell but when in moist air it acquires a smell of acetic acid. It has a flashpoint of 482° F. It is most widely used in medication to treat pain, inflammation, and fever.

Aspirin is one of the safest and most effective medicines and is extensively used medications globally, which is displayed on the WHO’s List of Essential Medicines.

Properties of Acetylsalicylic acid – C9H8O4

C9H8O4 Acetylsalicylic acid
Molecular Weight/ Molar Mass 180.159 g/mol
Density 1.40 g/cm³
Boiling Point 140°C
Melting Point 136°C

Structure of Acetylsalicylic acid – C9H8O4 

The structure of an acetylsalicylic acid molecule is illustrated below.

Structure of Acetylsalicylic acid

Acetylsalicylic acid (Aspirin) – C₉H₈O₄

Synthesis of Aspirin/Acetylsalicylic acid (C9H8O4)

Step 1: Dry an Erlenmeyer flask and add 3 grams of salicylic acid to it.

Step 2: Put 5 to 8 drops of 85% phosphoric acid along with 6 mL of acetic anhydride to the flask.

Step 3: Mix the solution and keep the flask in warm water for 15 minutes.

Step 4: To the warm solution, add 20 drops of cold water dropwise. (this destroys the excess acetic anhydride)

Step 5: Keep the flask in an ice bath to cool the mixture as well as for speed crystallization.

Step 6: On completing the crystallization process, pour the mixture with the help of a Buckner funnel.

Step 7: Use ice-cold water to wash the crystals to minimize the loss of the product.

Step 8: To purify the product perform recrystallization. Put the crystals in 10 ml of ethanol. Stir the mixture to dissolve the crystals.

Step 9: 25ml of warm alcohol is poured in it and covered to form crystals as the solution cools. Once the crystallization process begins, keep the beaker in an ice bath for recrystallization.

Step 10: The contents of the beaker are poured out and a suction filtration is applied.

Step 11: The excess water is removed from the crystals by keeping them on dry paper.

Step 12: To confirm acetylsalicylic acid, verify to a melting point of 135°C.

Uses of Acetylsalicylic acid (C9H8O4)

  • Acetylsalicylic acid acts as an inhibitor of cyclooxygenase.
  • It is used to prevent venous and arterial thrombosis.
  • It is used in the treatment of different types of headaches.
  • It is used as an anti-inflammatory agent for long-term as well as acute inflammation.
  • It is thought to reduce the overall risk of getting cancer, and dying from cancer.

Health Risks Associated with Acetylsalicylic Acid

  • Exposure pathways – Skin or eye contact, ingestion, and inhalation.
  • Symptoms – Irritation in eyes, upper respiratory system, skin, increased blood clotting time, vomiting, and nausea.

Practice Question

  1. Why is it necessary to wash aspirin with cold water?
  2. When acetic acid is added to the salicylic acid what happens to the OH group of the salicylic acid?

To learn more about the chemical reactions and structural details of Acetylsalicylic acid or aspirin (C9H8O4) from the expert faculties at BYJU’S register now!

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