SYNTHESIS OF ASPIRIN PURPOSE To synthesize acetyl salicylic acid (aspirin) and d
ID: 513861 • Letter: S
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SYNTHESIS OF ASPIRIN PURPOSE To synthesize acetyl salicylic acid (aspirin) and determine its yield and melting point. SYNTHESIS OF ASPIRIN Aspirin is made commercially by the following esterification reaction. Salicylic acid, the starting material in this procedure, can be made from phenol. which in tum is made from crude oil. Acetic hydride reacts with the hydroxyl group of the salicylic acid to produce an ester, acetylsalicylic acid, and a by-product, acetic acid. The rate of esterification is increased by addition of catalytic amounts of mineral acids, such as sulfuric or phosphoric acids. C CHs H,C C OH HJC C Salicylic acid this is the "vinegar" odor MICROSCALE PROCEDURE WEAR AN APRON CAUTION acetic anhydride is a lachrymator. Do any measuring or transferring of this chemical in the hood. Also, phosphoric acid is corrosive. Clean up any spills immediately by neutralizing with Liquid Neutralizer for Acids found in the safety cabinet 1. Set up a hot water bath (90 in a 100 mL beaker on a hot plate. 2. To a tared reaction tube, add 138 mg of salicylic acid, a boiling chip, and one small drop of 85% phosphoric acid. Add 0.30 mL of acetic anhydride. Mix the reactants thoroughly and then heat the reaction tube in the 90°C water bath for five minutes. 3. Remove the tube from the water bath. Use the syringe from the microscale kit to cautiously add 0.2 mL of DI water to the reaction mixture. This reacts with leftover acetic anhydride, converting it to acetic acid. The reaction is exothermic; hence, the need to add the water cautiously. When the reaction is over, add 0.3 mL more water and allow the tube to cool slowly, undisturbed, to room temperature in a beaker filled with cotton, Crystals of MICROSCALE HIRSCH FUNNEL FILTRATION acetylsalicylic acid should appear. If APPARATUSExplanation / Answer
using salicylic acid, acetic anhydride and a catalyst without solvents other than water and a small amount of ethanol for purification. Two modes of heating were used for this experiment: conventional heating (using a hot-plate) and microwave oven heating. With the conventional heating method, a 52.4% yield was obtained, while an 83.5% yield was obtained by microwave heating. The high-yielding microwave irradiation method also displayed higher purity with a melting temperature range of 128-132C (lit. 135C), while the conventionally heated ASA melted between 126-129C. Based on the results, one could suggest that microwave irradiation is a cleaner and more efficient way to produce acetyl salicylic acid. INTRODUCTION In experimental chemistry, especially synthetic, a lot of harmful solvents are used to improve reaction conditions and toxic by-products are often generated [1]. These chemicals are a source of pollution and are hazardous to the ecosystem. Given environmental concerns, chemists have been redesigning synthetic schemes in order to minimize the use and production of hazardous compounds [2]. In the synthesis of acetyl salicylic acid (aspirin), abbreviated as ASA, a popular drug, the principles of green chemistry are applied to improve its environmental friendliness. In classical synthesis, salicylic acid and acetic anhydride are refluxed with a strong acid in benzen
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