Preparation of Acetyl Salicylic Acid (Aspirin) Lab Report

Preparation of Acetyl Salicylic Acid (Aspirin) - Lab Report Example In the following experiment we embark to acquaint ourselves with a simple laboratory protocol for the synthesis of aspirin. This procedure will use acetic anhydride and sulfuric acid as the acid catalyst of the reaction. Objective: To illustrate the synthesis of the drug, aspirin and determine its purity by a chemical test Materials and methods: Synthesis of Aspirin A water- bath was prepared by filling half-way a 400mL beaker with water and the water heated to boiling point. 2.004g of salicylic acid was placed in a 125mL Erlenmeyer flask. Carefully 3mL of acetic anhydride was added to the flask and while swirling 3 drops of concentrated sulfuric acid were added. To avoid eye irritation and burns caused by acetic anhydride and sulfuric acid respectively, the chemicals were handled in the hood in gloves. The reagents were mixed and then the flask was placed in the boiling water-bath and heated for 15minutes. The setting of the practical is as shown in the diagram 1.1 below. This disso lved any solid while the solution was occasionally swirled. The Erlenmeyer flask was removed from the bath and left to cool to approximately the room temperature. The solution in the flask was then poured into a 150-mL beaker containing 20mL of ice water and mixed thoroughly before placing the beaker in an ice bath. The water destroyed any remnant of unreacted acetic anhydride and caused the insoluble aspirin to precipitate from the solution. The crystals were collected by filtering under suction with a Buchner funnel as shown in diagram 1.2 below. The side-arm of a 250mL filter flask was connected to a water aspirator with heavy wall vacuum rubber tubing. The Buchner funnel was inserted into the filter flask through a one-hole rubber stopper and a filter paper placed into the Buchner funnel making sure the paper covered all the holes. Finally the water was poured to the paper to wet it and then the water aspirator was turned on to a maximum water flow and the solution in the beaker poured into the funnel. The crystals were washed with two portions of cold water each 5mL and then followed by a one 10mL portion of cold ethanol. The suction of air was continued through the crystal for several minutes so as to dry them. The crystals were placed between several sheets of filter paper using a spatula and press-dried. A 50mL beaker was weighed before placing the crystals and reweighing the beaker. The weight and percentage yield of the crude aspirin was determined. Diagram 2: filtering using the Buchner funnel Procedure to determination of aspirin purity Three test tubes each 100 x 13 mm were labeled 1, 2, 3 and a few crystals of salicylic acid placed in the test tube-1 and in test tube-2 a small sample the newly synthesized aspirin was placed whereas for test tube-3 a small sample of crushed commercial was placed. In each of the test tubes, 5mL of distilled water was added and test tubes shaken to dissolve the crystals and a further 10 drops of 1% aqueous ferric ch loride was also added to each test tube. Observation and comparisons were made from the three test tubes and recorded. Results and Discussion Theoretical yield 2.004g salicylic acid X Weight of 50-mL beaker = 39.21 Weight of the aspirin and the beaker = 40.69 Weight of aspirin = Weight of the aspirin and the beaker - Weight of 50-mL beaker 40.69 – 39.21 = 1.48 g Weight of crude aspirin = 1.48 g Percent yield = 56.70% Chemical test with ferric chloride Presence of unreacted salicylic acid can be detected with 1% ferric chloride