Synthesis of paracetamol from p-aminophenol

Synthesis of paracetamol, synthesis of paracetamol from phenol, synthesis of paracetamol pdf, synthesis of paracetamol pdf download, paracetamol synthesis mechanism,

BACKGROUND

Principle: The synthesis of the amide essentially just requires running the reaction under certain temperature conditions with an appropriate catalyst. Paracetamol is prepared from p- aminophenol by acetylating it with acetic anhydride in the presence of 3-4 drops of concentrated sulphuric acid as catalyst.¹

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Aim: To prepare paracetamol from p-aminophenol.

Reaction:

Mechanism:

Uses:

It is an effective antipyretic and analgesic. Activity of the drug on the hypothalamic heat-regulating centre is the mechanism behind the antipyretic effect, whereas analgesia is shown due to elevation of the pain-threshold.

It is also found to be useful in diseases accompanied by pain, discomfort, and fever, for instance the common cold and other viral infections.² It is also active against arthritic and rheumatic disorders involving musculoskeletal pain as well as the pain occurred due to headache, myalgia, dysmenorrhea and neuralgia.

REQUIREMENTS

Chemicals:     

    p-Aminophenol – 6 g

    Acetic anhydride – 6.5 ml

    Concentrated Sulphuric acid – 4 drops

Apparatus:     

    Conical flask

    Buchner funnel

    Measuring cylinder

    Filter paper

PROCEDURE

Weigh 6 g of p-aminophenol and transfer to a 100 ml thoroughly cleaned and dried conical flask. Add to the flask 6.5 ml of acetic anhydride and 3–4 drops of concentrated sulphuric acid carefully. The contents of the flask may be mixed thoroughly. Warm the mixture on a water-bath previously maintained at 60°C for about 20–25 min with constant stirring.

Allow the contents of the flask to attain room temperature, and pour it directly into a beaker having 100 ml of cold water (with a few chips of crushed ice) and stir it vigorously.

The crude product obtained is filtered onto a Büchner funnel using suction, wash it with plenty of cold water, drain well and dry the product either between the folds of filter paper and air-dry it or dry it in an electric oven maintained at 100°C.

The yield of crude paracetamol (169–170.5°C) is approximately 6.8 g.

Recrystallisation

Dissolve the crude product in 70% (v/v) ethanol and warm it to 60°C; add 2 g of powdered animal charcoal (decolourizing carbon). Filter and concentrate the filtrate over a water-bath. Allow it to cool and large monoclinic crystals will separate out. The yield of the pure paracetamol (m.p. 169–170.5°C) is 6.5 g.

Precautions

All glass apparatus must be perfectly dry. Concentrated sulphuric acid should always be added with great caution.

Calculation

Here limiting reagent is p-aminophenol; hence yield should be calculated from its amount taken.

Molecular formula of p-aminophenol = C₆H₇NO

And molecular formula of paracetamol = C₈H₉NO₂

Molecular weight of p-aminophenol = 109 g/mole

Molecular weight of paracetamol = 151 g/mole

Theoretical yield:

109 g p-aminophenol forms 151 g paracetamol

Therefore, 6 g p-aminophenol will form ………? (X) g paracetamol

X =( 151 × 6)/109 = 8.31 g

Theoretical yield = 8.31 g

Practical yield = ————- g

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

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CONCLUSION

Paracetamol was synthesized and the percentage yield was found to be………..%.

REFERENCES

1. Vogel’s Textbook of Practical Organic Chemistry by Brian S. Furniss, Antony J. Hannaford, Peter W. G. Smith & Austin R. Tatchell; Fifth Edition; Page No.- 985.
2. Advanced Practical Medicinal Chemistry by Ashutosh Kar; New Age International (P) Limited Publishers (2004); Page No. 88.

Also read:

• Synthesis of benzilic acid from benzoin
• Synthesis of acetaminophen (paracetamol) from p- aminophenol by using microwave system
• Synthesis of p-nitroaniline from acetanilide
• Synthesis of p-aminophenol from nitrobenzene
• Synthesis of aspirin from salicylic acid using acetic anhydride
• Synthesis of m-nitrophenol from nitrobenzene
• Synthesis of methyl salicylate
• Synthesis of methyl orange from sulphanilic acid

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