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Aspirin Investigation

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OBJECTIVES The objectives of this investigation are: 1) Research available literature on aspirin with reference to synthesis, history, and medical use. 2) Prepare a pure sample of aspirin starting with oil of wintergreen as the initial compound. 3) Verify the identity and measure purity of the manufactured aspirin using a range of techniques. 4) Devise additional investigations into manufacture, properties or usage of Aspirin. Background Information Aspirin or acetylsalicylic acid is made from salicylic acid, found in the bark of the willow tree, which was used by the ancient Greeks and Native Americans, among others, to counter fever and pain. Salicylic acid is bitter and irritates the stomach. The German chemist Felix Hoffman synthesized the acetyl derivative of salicylic acid in 1893 in response to the urging of his father, who took salicylic acid for rheumatism. Aspirin is currently the first-choice drug for fever, mild to moderate pain, and inflammation due to arthritis or injury. It is a more effective analgesic than codeine. Aspirin causes insignificant gastrointestinal bleeding that can over time, however, cause iron deficiency; gastric ulcers may also occur with long-term use. Complications can be avoided by using enteric-coated aspirin, which does not dissolve until reaching the intestine. Aspirin should not be given to children who have chicken pox or influenza, because it increases the risk of contracting the rare and frequently fatal Reye's syndrome, a disease of the brain and some abdominal organs. Aspirin is thought to act by interfering with synthesis of prostaglandins, which are implicated in inflammation and fever. Studies of aspirin's anticlotting activities suggest that half an aspirin tablet per day may reduce the risk of heart attack and stroke in some persons. Timeline: BC 400 Greece Hippocrates prescribes willow leaf tea to alleviate the pain of childbirth in. 1763 Oxford Reverend Edward Stone of Chipping gives dried willow bark to fifty parishioners who are suffering from rheumatic fever. ...read more.


0.0333 / 0.7 = 0.4762 mol Salicylic Acid (Moles x RMM = mass = 0.4762 x 138.1 = 6.571g Salicylic Acid) Assumed yield: 70% (Oil of Wintergreen --> Salicylic Acid) 0.04762 / 0.7 = 0.0680 mol Oil of Wintergreen (Moles x RMM = mass = 0.0680 x 152.1 = 10.347g Oil of Wintergreen) Therefore actual starting amounts: 10.35g Oil of Wintergreen (Methyl Salicylate) 20.69g Sodium Hydroxide 103.5 cm3 Distilled Water APPARATUS 250 ml conical flasks Anti-bump granules Beakers Buchner filter assembly Burette Crushed Ice Dilute Distilled water Ethanoic anhydride - 8.76cm3 Glacial ethanoic acid Heatproof mat Microburner Oil of wintergreen (2 methyl-2-hydroxybenzoate) - 10.35g Reflux apparatus Retort stand, boss head and clamp Sodium hydroxide - 20.69g METHOD PART ONE I. Mix 10.35g oil of wintergreen, 20.69g sodium hydroxide and 103.5 cm3 of water in a 250cm3 conical flask. II. Drop in a few anti-bump granules, attach a reflux condenser to the flask, and boil gently using a Microburner (or heating mantle) for 20 minutes. III. When the flask has cooled pour the contents into a conical flask surrounded by crushed ice in a large beaker. IV. Add dilute sulphuric (VI) acid to the cold hydrolysate until the precipitation of the 2-hydroxybenzoic acid is complete. V. Filter off the precipitate using a Buchner funnel, washing once with iced water. VI. Re-crystallize from hot water, cooling with iced water. VII. Filter with Buchner funnel VIII. Leave to dry in air, weigh and calculate the yield. APPARATUS 100 cm3 conical flasks 250 ml conical flasks Buchner filter assembly Concentrated sulphuric (VI) acid Distilled water Dropper Ethanoic anhydride 8.76cm3 Filter funnel Hydroxybenzoic acid 6.57g Ice water Safety glasses Stirring rod Watch glasses Water Bath METHOD PART TWO I. Shake 6.57g of 2-hydroxybenzoic acid with 8.76cm3 of ethanoic anhydride in a 100 cm3 conical flask. II. Add ten drops of concentrated sulphuric (VI) acid and continue agitating the flask as it cools, warm in a water bath for fifteen minutes. ...read more.


Evaluation So as to achieve a reasonable amount of final product I assumed yield of seventy percent in both reaction steps; the aim of this was to get 6g of Aspirin. Therefore I had to deviate from the original method by recalculating the initial reagent amounts, however I did list these values in the method section. I believe the yield of aspirin achieved was quite satisfactory for a school laboratory investigation, however to explain the loss in yield: we may not have allowed the aspirin crystals sufficient time to crystallize after leaving the solution water overnight (If I were to repeat the experiment I would allow the solution longer for crystallization) Also, when sulphuric acid was added to the 2-hydroxybenzoic acid and ethanoic anhydride mixture in the conical flask, there may well have been incomplete crystallization occurring before filtering the solution using the Buchner apparatus - there was no method of determining the occurance of complete crystallization. An improvement would be to remove the crystals and add more sulphuric acid to the 2-hydroxybenzoic acid. Aspirin crystals dissolving in the water when the aspirin was washed and filtered would have been another problem. The entire experiment involved numerous tranfers between containers and some mass of product is likely to have been lost in transit. Moisture in the air may have affected the purity of the sample, and various human errors involved in measuration are also certain to have taken place. Suggestions for Further Investigation It would be possible to investigate the advantage/disadvantages of alternative acylating agents. In this experiment I used ethanoic anhydride but for example, It is also possible to use ethanoyl chloride or ethanoic acid. Other investigations could include experimentation with hydrolysis rate in step one, or a melting point analysis for purity and identification of the products obtained. Sources: Internet: http://www.aspirin.org/ The Aspirin Organization http://info.bayerus.com/ The Bayer Company In America http://www.mjm.mcgill.ca/ Misc. Homepage http://www.nyu.edu/ University of New York (Coverpage Molecule) Organic Chemistry In the Laboratory; Mei Tak Yip and David Dalton Operational Organic Chemistry; John W. Lehman Organic Experiments (5th Edition) Louis F. Fieser and Ken Williamson 14 ...read more.

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