Acetylsalicylic Acid or Aspirin

What is Acetylsalicylic Acid or Aspirin?

Aspirin is a general medication used for pain, fever, inflammation, heart attacks etc. It is commonly prescribed for because of its properties such as anti – inflammatory, anti – coagulatory, fever reducing and pain relieving. The major component of aspirin is acetylsalicylic acid which gives it all these properties. This is the reason aspirin is also known as acetylsalicylic acid. Its molecular formula is C9H8O4

Aspirin is NSAID (Nonsteroidal anti-inflammatory drug) but it suppresses the normal functioning of platelets. It is not recommended during pregnancy and to children with infections. It has various side effects as well such as high dose may result in the ringing of ears, Reye syndrome, nausea, upset stomach, headache etc. 

Acetylsalicylic acid was first produced by Alsatian Chemist Charles Frederic Gerhardt in 1853 from sodium salicylate and acetyl chloride. Soon the drug became famous and Bayer (a drug and dye firm) started producing it at large scale. Bayer named it Aspirin. It was Bayer’s brand name for the drug. Its popularity declined in 1962 after the synthesis of drugs like paracetamol and ibuprofen. 


Formula of Acetylsalicylic Acid 

S. No.

IUPAC Name & Formula of Acetylsalicylic Acid 

1.

Empirical Formula 

C9H8O4

2.

Molecular Formula 

CH3COOC6H4COOH or C9H8O

3.

Skeletal formula

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4. 

IUPAC name 

2-acetoxybenzoic acid 

5. 

Other general names 

Acetylsalicylic acid, aspirin, acetylsalicylate. 


Structure of Acetylsalicylic Acid 


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Properties of Aspirin 

Physical Properties of Aspirin – It Shows Following Physical Properties

  • Its molar mass is 180.16 g/mol.

  • Its melting point is 136 .

  • Its boiling point is 140 .

  • It's soluble in water. 3g of aspirin can dissolve in 1 liter of water. 

  • It is a white crystalline solid at room temperature. 

  • It is weakly acidic in nature. At 25 temperature, its acid dissociation constant is 3.5. 

  • Its density is 1.40 g.cm-3


Chemical Properties of Aspirin – It Shows Following Chemical Properties

  • It gets hydrolyzed on coming in contact with moist air. Although it is stable in dry air. 

  • It easily decomposes in the solution of ammonium acetate, carbonates, citrates or alkali metal hydroxides.

  • It can be explosive when mixed with air in its powdered form. 

  • It is anti-inflammatory, anti – coagulatory and analgesic.  


Synthesis of Acetylsalicylic Acid 

Aspirin is synthesized by the action of salicylic acid on acetic anhydride. It is an esterification reaction. In this reaction, when salicylic acid reacts with acetic anhydride, the hydroxyl group of salicylic acid converts into an ester group. This results into aspirin and acetic acid. Sulfuric acid or phosphoric acid act as catalysts. Reaction is given below 

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Uses of Acetylsalicylic Acid/Aspirin 

Acetylsalicylic acid is mainly used in the medical field. Few of its medical uses are listed below –

  • It is an analgesic and used to get relief from acute pain. 

  • It is highly effective against muscle pain, bloating, skin irritation, gastric distension. 

  • It is also used for the treatment of migraine. 

  • It is effective against cluster headache. 

  • It is used in fever. 

  • It is anti-inflammatory so it is used to treat inflammation. 

  • It is useful in the treatment of those parts of the heart which had an attack. 

  • Aspirin is advised to take after surgeries like PCIs etc. 

  • It reduces the risk of getting cancer. 


Side effects of Aspirin 

Although aspirin is very useful against many diseases, but it has various side effects as well. It must not be taken in very high amounts because in very high concentrations acetylsalicylic acid may cause hallucinations and even death. 

It causes nausea, vomiting, bloating, muscle cramps, gastrointestinal irritation, gastritis, diarrhea, gastric ulcer, decrease in blood pressure, drowsiness, headache, heartburn etc.   


Aspirin: Summary in Tabular Form 

Aspirin 

Chemical formula 

CH3COOC6H4COOH or C9H8O4

IUPAC Name 

2-acetoxybenzoic acid 

Other names 

Acetylsalicylic acid, aspirin, acetylsalicylate. 

Molar mass 

180.16 g/mol

Melting point 

136 ℃

Boiling point 

140 ℃

Density 

1.40 g.cm-3

Appearance 

White crystalline 

Odor 

Like vinegar (at higher concentrations)

State at STP

Solid 

Solubility in water 

Soluble (3g.L-1)

Preparation 

By the reaction of salicylic acid and acetic anhydride in the presence of sulfuric acid/ phosphoric acid as catalyst. 

C6H4(OH)COOH + (CH3CO)2O 🡪 CH3COOC6H4COOH + CH3COOH 

Main properties 

Anti-inflammatory, Analgesic 

Main use 

To get relief from pain, fever, headache etc. 

Disadvantage 

Causes side effects like nausea, muscle cramps, bloating. 


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