Synthesis of Aspirin

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The Synthesis of Aspirin

Chemistry Standard Level Lab Report

Data Collection and Processing and Conclusion and Evaluation

Date: December 8th, 2011


The purpose of this lab was to synthesize aspirin, determine the theoretical yield, compare the percent yield to the theoretical yield and test the purity of aspirin by adding Iron (III) chloride to the product.


I hypothesize that salicylic acid will react with acetic anhydride to produce acetylsalicylic acid (aspirin) and acetic acid (vinegar).


Independent and controlled variables: The amount of sulfuric acid used for catalysis and the amount of salicylic acid and acetic anhydride. Dependent variables: Theoretical and actual yield of aspirin. Constant variables: Two beakers filled with 200 mL of water for the boiling water bath, the cold water bath and the temperature of the boiling water bath and cold water bath.


Safety goggles, Lab coat, protective rubber gloves, notebook for observations, pen or pencil, four trays, 3 grams of salicylic acid, 125 mL Erlenmeyer flask, 8 mL of acetic anhydride, 8 drops of concentrated (85%) phosphoric or sulfuric acid, five 10 mL graduated cylinders, 50 mL graduated cylinder, hot plate, stirring rod, two 400 mL beakers, one 250 mL beaker, ring stand, utility clamp, filter paper, funnel, stopwatch, balance, two pipettes, scoopula, 6 test tubes, test tube stand, 0.1 grams of salicylic acid, 0.1 grams of commercial aspirin, 0.1 of handmade aspirin, 2.0 mL of Iron (III) chloride and cold water bath.


All the materials needed to begin were collected and the goggles, gloves and lab coat were worn for safety purposes. All the observations of synthesis of aspirin were recorded in tables in a notebook.

Preliminary steps:

The hot plate was set up first. A 400 mL beaker was filled with 200 mL of water and placed on the hot plate to boil. 3 mL of cold water and 60 mL of water were measured and prepared with a graduated cylinder. A 400 mL beaker was filled with 200 mL of cold ice water to prepare a cold water bath. A gravity filtration system was set up using filter paper, ring stand, utility clamp and a 250 mL beaker. The filter paper was weighed and subsequently placed in the funnel.

Procedure of the synthesis of aspirin:

3.00 grams of salicylic acid were weighed and placed in a 125 mL Erlenmeyer flask. Initial observations of salicylic acid were recorded.

8 cm3 (cm3 = mL) of acetic anhydride was carefully measured in a 10 mL graduated cylinder. Initial observations of acetic anhydride were recorded.

8 drops of concentrated (85%) sulfuric acid was directly added to the acetic anhydride, using a pipette, which was then immediately added to the Erlenmeyer flask containing salicylic acid. Observations of the two solutions mixed together were recorded.

The aqueous solution of salicylic acid and acetic anhydride was stirred thoroughly and then heated, using a hot plate, in a boiling water bath for 5 minutes. Initial observations of the solution were recorded before the solution was heated in the boiling water bath. The solution in the flask was stirred frequently.

The solution was removed from the boiling water bath and 3 mL of cold water was added immediately to the solution while stirring. Observations of the solution were recorded after the solution was heated in the boiling water bath. Observations were also recorded after adding the 3 mL of cold water to the solution. The solution was stirred for a couple minutes after being removed from the boiling water bath in order to destroy any excess acetic anhydride. The solution was then stirred while adding 60 mL of water. Observations were recorded after adding 60 mL of water to the solution. A precipitate began to form in the solution, and the solution in the Erlenmeyer flask was placed in a cold water bath for 5 minutes to complete the formation of aspirin crystals. Observations were recorded...
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