SYNTHESIS OF ACETAMINOPHEN Cautions for experiment: Handle p-aminophenol carefully - wear gloves Acetic anhydride is toxic, corrosive and a lachrymator (causes tears) and a skin irritant. Avoid contact with skin, eyes and clothing. USE ACETIC ANHYDRIDE IN A FUMEHOOD WHENEVER POSSIBLE Hydrochloric acid is a skin irritant. EXPERIMENTAL PROCEDURE Place 1.05 g of p-aminophenol and 20 mL of water in a 125-mL Erlenmeyer flask. Add 1.0 mL of concentrated hydrochloric acid, and swirl the flask for a few minutes to ensure that the amine dissolves completely. If some amine remains undissolved, warm the mixture on a steam bath until all the material is in solution. Prepare a solution for use as a buffer (this prevents the reaction pH from changing significantly) by dissolving 1.25 g of sodium acetate tri-hydrate (CH3CO2Na.3H2O) in 3.0 mL of water. If required, clarify the solution by gravity filtration. Add the sodium acetate buffering solution in one portion. Immediately add 1 mL of acetic anhydride while swirling the solution. Continue swirling the solution vigorously for at least 10 minutes to ensure mixing. If the solution is highly colored then it can be purified using charcoal: add a spatula full of decolorizing charcoal to the solution, swirl the solution on a steam bath for a few minutes, and remove the charcoal by gravity filtration, using a fluted filter. Cool the reaction mixture by immersing the flask in an ice-water bath, and stir the mixture vigorously until the crude acetaminophen crystallizes. It may be necessary to scratch the walls of the flask vigorously in order to initiate crystallization. Allow the flask to remain in the ice bath for about 15 minutes. Collect the crystals in a Büchner funnel by vacuum filtration. Wash the crystals with a small portion (20mL) of ice cold water. Leave the crystals on the filter paper in the Büchner funnel under vacuum to dry. Once dry, weigh the acetaminophen crystals, calculate the percentage yield and determine the melting point.