The Melting Point Analysis of Crude and Recrystallized Acetaminophen Synthesized from P-Aminophenol and Acetic Anhydride

1099 words 5 pages
Abstract Acetic Anhydride and p-Aminophenol were heated in a vial attached to an air condenser to synthesize crude acetaminophen, resulting in 0.097 grams (47.48% yield). The crude acetaminophen was then recrystallized in a solvent of water and methanol over heat resulting in 0.082 grams (39.61% yield) of pure acetaminophen. Melting points of both crude and pure acetaminophen were taken, and found to be 165.9 - 170.9°C and 168.2 - 171.5°C, respectively. The literature melting point of acetaminophen is 169.5 – 171.0°C, indicating that our final product was pure.

Introduction The synthesis of acetaminophen involves the attraction of the electrophilic carbonyl group of acetic anhydride to the nucleophilic NH2
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The resulting crystals (o.o82g) were pale brown in color. Melting points were taken for both the crude (165.9 – 179.9°C) and the pure (168.2 – 171.5°C) acetaminophen.
Results and Calculations

Moles p-aminophenol :
0.150 g x (1 mol )/(109.1 g )= 0.00137 mol ← p-aminophenol is the limiting reagent

Moles of acetic anhydride:
0.165 mL x (1.08 g)/(1 mL) x (1 mol )/(102.1 g)=0.00174 mol
Theoretical Yield:
0.00137 mol x (151.2 g)/(1 mol)=0.207 g

Percent yield of crude acetaminophen:
Crude crystal weight = 0.089 g
(0.089 g)/(0.207 g) x 100%=46.48 %

Percent yield of pure acetaminophen:
Pure acetaminophen weight = 0.082 g
(0.082 g)/(0.207 g) x 100%=39.61 %

Literature value of acetaminophen melting point = 169.5 – 171.0°C
Crude acetaminophen melting point = 165.9 – 170.9°C
Recrystallized acetaminophen melting point = 168.2 – 171.5°C
Discussion and Conclusions Crude acetaminophen was successfully synthesized, forming light brown crystals. All of the solid was allowed to dissolve, and the mixture was adequately heated. The crystals were allowed plenty of time to fully cool. A percent yield of 46.48% was achieved, with a total of 0.089 g being formed. Recrystallization was done on the crude product, resulting once again in light brown crystals. All of the solid was dissolved in the hot solvent, and crystallization occurred once induced by scratching the inside of the tube. The crystals were properly cooled, and