CHEM 231L - Synthesis of Aspirin (Acetylsalicylic Acid) Dr....

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Synthesis of Aspirin (Acetylsalicylic Acid) Dr. Gergens - SD Mesa College Purpose: To prepare the common drug aspirin, an ester derivative of salicylic acid, by the acylation reaction of salicylclic acid with acetic anhydride. Acetic anhydride is the acylation reagent used in the production of aspirin. Reading: "Zubrick" pp. 149-168. Useful Web sites: Background: Over history, many compounds obtained from nature have been used to cure ills or to produce an effect in humans. In the late 1700's, chemists working with willow bark extract identified the active ingredient salicylic acid as compound that could feverish symptoms of several diseases. Salix is the Latin name for the willow tree. Using salicylic acid as a remedy, however, was severely limited by its acidic properties, causing severe irritation of the stomach. It wasn't until 1893 when Felix Hofmann, a chemist for the German firm of Bayer, devised a practical route for synthesizing acetylsalicylic acid, which was found to have all the same medicinal properties without the serve degree of stomach irritation caused by salicylic acid. Today, one of the best known aromatic acetates is acetylsalicylic acid, or aspirin, which is prepared by the esterification of the phenolic hydroxyl group of salicylic acid. Aspirin (acetylsalicylic acid) is the most widely used drug in the world. Hundreds of millions of dollars are spent annually on this compound. It is used primarily as a pain reliever (analgesic) and in the reduction of fever (antipyretic). Both these pharmaceutical properties has made aspirin one popular drug. PRE-LAB 1. Write a title and purpose for this experiment into your laboratory notebook. 2. After your purpose, write the main reaction. 3. On the pages following the main reaction, draw the mechanism, physical separation flow chart and purification scheme, and data table into your notebook. 4. Have your instructor initialize items 1-3 in your notebook prior to doing any laboratory work.
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Main Reaction Mechanism
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General Physical Separation and Purification Scheme
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Data Table compound grams molar mass moles mole ratio Theoretical Actual mp bp miscellaneous reactant T A C7H6O3 138.12 1 159°C 211°C @ 20 mm Hg moisture sensitive; light sensitive C4H6O3 102.09 1 -73°C 140°C colorless liquid with a characteristic sharp odor. lachrymator/moisture sensitive H3PO4 98 catalyst 21 260 hygroscopic. solvent H2O product
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C9H8O4 180.16 1 135°C 140°C Analgesic, anti-inflammatory and antipyretic. White crystals or white crystalline powder By-Products
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The Experiment_ Step 1. Place 2.O g (O.O15 mole) of salicylic acid in a 125-mL Erlenmeyer flask with a Teflon stir bar. Step 2. Add 5 mL (O.O5 mole) of acetic anhydride, followed by 5 drops of 85% phosphoric acid, H3PO4. Measure the acetic anhydride under the hood since it is highly irritating to the nose. Stir the flask thoroughly until the salicylic acid dissolves. Step 3.
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CHEM 231L - Synthesis of Aspirin (Acetylsalicylic Acid) Dr....

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