Preparation of Acetyl Salicylic Acid (Aspirin) - Lab Report Example

?Preparation of Acetyl Salicylic Acid (Aspirin) 13th December Introduction: Aspirin is the most widely used over the counter non-prescription drug in the United States. The drug is an effective analgesic that can reduce nerve pain, toothache and headache. It also acts as an antipyretic drug where it reduces fever and an anti-inflammatory agent capable of reducing the swelling and redness associated with inflammation. Due to its ability to acts as an anticoagulant, aspirin is an effective agent in the prevention of strokes and heart attack. 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 dissolved 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 chloride 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 which reacts with the phenol group in salicylic acid to give a violet color. This is the absolute test for a pure sample of aspirin which will not react with the ferric chloride. The aspirin from our experiment had a violet color as seen below in plate 1 indicating there was some salicylic acid which did not react. In plate 2 below is a spectrum obtained from our dried purified aspirin from the analyses carried in the Fourier Transform Infrared (FTIR) spectrophotometer. The functional groups are recognized from their various absorption peaks that are observed in the spectrum. A comparison was made between the spectrums generated from our re-crystallized sample and a known spectrum of aspirin in figure 1 below. The IR spectrum of Acetylsalicylic acid (aspirin) is as shown below Figure 1: Known spectrum of acetylsalicylic acid Absorption peaks for the functional groups present in aspirin C=C (aromatic), 1600 – 1400cm-1 C=O (ester), 1750 – 1730cm-1 C=O (carboxylic acid), 1725 – 1700cm-1 C-O (ester/carboxylic acid), 1300 – 1000 cm-1 O-H (carboxylic acids), 3300 – 2500 cm-1 The spectrum obtained from our experiment did not replicate the known absorption peaks for the various functional groups present in acetylsalicylic acid. This indicates that our sample failed the purity test and may be contaminated with unreacted reactants. Prelab questions 1. A person took aspirin because it is an antipyretic. What is the trying to accomplish Aspirin has anti –inflammatory potential where it reduces the swelling and redness symptoms which accompany inflammation. 2. Draw the structure of aspirin. Should this compound test positive with 1% ferric chloride solution? Explain your answer. No, aspirin is not a phenol and will not form the violet color in the presence of ferric compound. Usually a positive test with 1% ferric chloride indicates the presence of a phenol. 3 ArOH + FeCl3 3. Aspirin can irritate the stomach. What is usually done in the formulation of the drug that reduces this side effect? The active agent in aspirin, salicylic acid contains the phenolic group and carboxylic acid that results in the compound being harsh to the stomach lining. A formulation of the drug with ester acetylsalicylic acid is a lesser irritant and does not irritate the stomach. The ester hydrolyzed in the small intestine to salicylic acid which was absorbed into the bloodstream. In order to lower the irritability of this drug, the drug is coated with magnesium hydroxide, magnesium carbonate and Aluminium glycinate which are mixed into a formulation of aspirin. 4. What is the active ingredient that gives aspirin its therapeutic properties? Salicylic acid is the active agent that confers aspirin with the therapeutic properties. 5. What is the purpose of the concentrated sulfuric acid in the preparation of aspirin? Could some other acid be used? Sulfuric acid is the acid catalyst that speeds up the reaction of acetic anhydride with salicylic acid in the formation of aspirin though phosphoric acid can be used in place of sulfuric acid. 6. If in step no. 11 of the procedure, you failed to dry completely your aspirin preparation by omitting the drying between filter paper, what would happen to your percent yield? The percent yield is a ratio of the actual aspirin from the experiment verses the theoretical aspirin weight therefore omitting this step will led to a higher actual weight of aspirin hence giving a higher percent yield of aspirin which is false. 7. A student expected 8.4 g of acetylsalicylic acid, but obtained only 5.3g. What is the percentage yield? 5.3/8.4% Percentage yield = 63.10% 8. Tylenol also is an analgesic often taken by people allergic to aspirin. The active ingredient is acetaminophen . Would acetaminophen give a positive phenol test? Explain your answer. Does this compound contain the ester functional group? If not, what functional group is present? Yes, it has a phenol group in its structure and therefore will give a positive phenol test. This compound lacks an ester functional group and in its place is an ethanamide group. Conclusion The experimental results indicate that our aspirin was not in pure form as demonstrated by the ferric chloride chemical test and the absorption peaks of the various functional groups in the molecule as seen in the spectrum obtained from Fourier Transform Infrared spectrophotometer. In conclusion we were able to demonstrate a simple protocol for synthesizing aspirin and also demonstrated how the purity of this substance can be determined. Read More