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ASPIRIN PREPARATION The molecular formula for aspirin is C9H8O4, it contains a benzene ring. Its structural formula is H3CCOO. Aspirin was one of the...

aspirin calculation
ASPIRIN PREPARATION The molecular formula for aspirin is C 9 H 8 O 4, it contains a benzene ring. Its structural formula is H 3 CCOO.C 6 H 4 .COOH. Aspirin was one of the earliest known remedies for the relief of fever (antipyretic) and pain (analgesic). The active analgesic is 2-hydroxybenzoic acid (salicylic acid), but this is a sufficiently strong acid to irritate the stomach and the ethanoyl ester, being less acidic, is used as the preferred medicine. The sodium salt is sometimes used, this has a higher solubility than the free acetylsalicylic acid and is also less likely to cause an acid reaction in the stomach - it is basic. Under the (usually) alkaline conditions found in the intestine the ester is hydrolysed to the free acid, which is then absorbed in the blood stream. CHEMICAL EQUATION HO.C 6 H 4 .COOH + (CH 3 CO) 2 O H 3 CCOO.C 6 H 4 .COOH + CH 3 COOH 2-hydroxybenzoic acid aspirin Background theory Aspirin is the trade name for the molecule acetylsalicylic acid it is use in the olden days to cure headache fever, use to cure heart disease e.t.c. The earliest known use of this molecule has been traced back to the fifth century B.C. The Greek physician Hippocrates described an extract of willow tree bark, a bitter powder that could be used to reduce fevers. In 1829, Salicin was isolated from willow bark and used as a pain reliever. Unfortunately Salicin was not very popular since it was found to be very acidic and a stomach irritant. In 1897 a German chemist named Felix Hoffman was working for the Bayer chemical company. Hoffman was looking for a less acidic pain reliever that his father could take for his arthritis. His research led to the synthesis of acetylsalicylic acid (ASA) or aspirin. SAFTYETY PRECAUTIONS 1. Wear safety glasses or goggles at all times in the laboratory. 2. Ethanoic anhydride is corrosive and flammable. Avoid eye contact 3. 2-hydroxybenzene-carboxylic acid is harmful to eyes, lungs and skin 4 concentrated phosphoric acid is corrosive 5. Ethanoic anhydride is volatile and irritating, concentrated sulphuric acid is corrosive. Use a fume cupboard, wear goggles and plastic gloves to handle all the chemicals.
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THE PREPARATION OF ASPIRIN Materials Needed Salicylic acid Acetic anhydride Ethanol Dropper Erlenmeyer flask, 125-mL Beakers, 2 400-mL, 100-mL, 10 or 20-mL Graduated cylinders, 10-mL, 25-mL Watch glass Stirring rod Vial to hold aspirin sample Ring stand Clamp (to hold 125-mL Erlenmeyer flask) Buchner funnel Filter paper to fit Buchner funnel Vacuum filtration flask Rubber tubing for vacuum flask Ice Thermometer, 110 ° C Melting point capillary tube Melting point apparatus Dropper Disposable IR card Optional: rubber gloves. Procedure 1. Weigh out around 2.0 g of salicylic acid. 2. Put about 4 cm 3 to 5cm 3 of ethanoic anhydride into a flask. 3. Add the salicylic acid to the flask as well. 4. Add 5 drops of phosphoric acid to the reaction mixture in the flask and swirl to mix.
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This question was asked on Mar 16, 2010.

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