Synthesis of Aspirin from Salicylic Acid using Acetic Anhydride

Aspirin

Synthesis of aspirin procedure, synthesis of aspirin mechanism, aspirin lab report pdf, salicylic acid + acetic anhydride = aspirin + acetic acid balanced equation, synthesis of acetylsalicylic acid lab report, synthesis of aspirin lab report discussion, acetylation of salicylic acid

BACKGROUND

Principle: Synthesis of aspirin from salicylic acid occurs by acetylation process in acidic medium. Salicylic acid interacts with acetic anhydride in presence of few drops of concentrated sulphuric acid to produce aspirin and a molecule of acetic acid.

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The purpose of adding sulphuric acid (catalyst) is to aid and augent the process of detaching the acetate ion (CH₃COO^–) from acetic anhydride which ultimately gets associated with H⁺ ion from phenolic hydroxy group in salicylic acid to be eliminated as a mole of acetic acid.¹

Aim: To prepare aspirin from salicylic acid.

Reaction:

Mechanism:

Use:

Synthesis of aspirin from salicylic acid is used for the relief of minor pains/aches and even mild to moderate pain. It is recommended for arthritis and related arthritic conditions, myocardial infarction prophylaxis. It reduces the risk of transient ischemic attacks in men.

REQUIREMENTS

Chemicals:     

• Salicylic acid – 6 g
• Acetic anhydride – 8.5 ml
• Concentrated H₂SO₄ – 3-4 drops
• Methylated spirit

Apparatus:     

• Conical flask – 250 ml
• Buchner funnel
• Glass rod
• Beaker
• Filter paper

PROCEDURE

Weigh 6 gs of salicylic acid and transfer it to a clean and dry 250 ml conical flask.

Add 8.5 ml acetic anhydride and 3-4 drops of concentrated sulphuric acid to the flask carefully and mix thoroughly.

Warm the mixture on water bath at 60 degrees about 20 min with frequent stirring.

Allow the contents in the flask to cool and pour into 100 ml cold water in 250 ml beaker with constant Stirring.

Filter the crude product on a Buchner funnel using suction, wash with cold water.

Recrystallize from boiling water along with small quantities of methylated spirit. Dry the synthesized product in an oven at 90 °C and calculate the yield.

Calculation

Here limiting reagent is salicylic acid; hence yield should be calculated from its amount taken.

Molecular formula of salicylic acid = C₇H₆O₃

And Molecular formula of acetylsalicylic acid (aspirin) = C₉H₈O₄

Molecular weight of salicylic acid = 138 g/mole

And Molecular weight of acetyl salicylic acid (aspirin) = 180 g/mole

Theoretical yield:

138 g of salicylic acid gives 180 g of aspirin

Therefore, 6 g of salicylic acid will give ? (X) g of aspirin

X =( 180 × 6)/138 = 7.82 g

Theoretical yield = 7.82 g

Practical yield = ————- g

% Yield = (Practical Yield)/(Theoretical Yield) × 100

CONCLUSION

Aspirin was synthesized and the yield was found to be ——— %. (The product is obtained as colourless crystals, yield 11 g and m.p. 136-137 °C.)

REFERENCES

1. Vogel’s text book of Practical Organic Chemistry, Page No. 1290.
2. Practical Organic Chemistry by Frederick George Mann and Bernard Charles Saunders Published by Longan Inc., Fourth Edition; Page No. 110.

Also read:

• Synthesis of acetanilide from aniline
• Synthesis of benzil from benzoin
• Synthesis of paracetamol from p-aminophenol
• Synthesis of p-bromoacetanilide from acetanilide
• Estimation of protein by Folin Lowry method
• Synthesis of acetaminophen (paracetamol) from p- aminophenol by using microwave system
• Synthesis of p-nitroaniline from acetanilide
• Synthesis of p-aminophenol from nitrobenzene

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