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Sally Solomon,(1) Chinhyu Hur, Alan Lee,(2) and Kurt Smith Drexel University, Philadelphia, PA 19104
This multistep organic synthesis of ethyl salicylate from aspirin tablets is intended as a laboratory activity to accompany introductory courses that devote time to topics in organic chemistry. The experiment is for high school or university students with sufficient background in organic chemistry to recognize the structures and reactions involved. At Drexel University this experiment is included in a general-chemistry sequence for science and engineering majors where topics in organic chemistry are covered.
Ethyl salicylate is synthesized, isolated, and characterized in a three-step process using simple equipment and household chemicals. The procedure can be done with a minimum of glassware, a hot plate, and a supply office. The entire synthesis requires a minimum of two laboratory class periods. The following steps are involved.
* Acetylsalicylic acid (ASA) is extracted from aspirin tablets with isopropyl alcohol.
* ASA is hydrolyzed to salicylic acid (SA) with muriatic acid.
* SA is esterified using ethanol and a boric acid catalyst.
Isolation of the ester product can be accomplished by treatment with lye solution (without saponification of the ester) to remove unreacted acid, followed by physical separation of the water-insoluble, pleasant-smelling oil of ethyl salicylate. The product is dried with dehydrated Epsom salts. For a class of 20, the table lists the chemicals; all are readily available in drugstores, supermarkets, hardware stores, or variety stores, so they require no special waste-disposal methods. The cost per pair of students is less than one dollar.
Procedure
Isolation of ASA from Aspirin Tablets
Caution: Although this experiment uses household materials, students should obey standard laboratory safety rules such as the wearing of safety glasses and careful handling of flammable liquids.
If only two lab periods are available, the second step, a hydrolysis, can be carried forth using wet product, allowing both isolation and hydrolysis to be finished in a single 2- or 3-h laboratory class. With this procedure the yield can only be estimated.
Aspirin tablets each contain 325 mg (5 gr) of ASA and about 50 mg of inactive starch and cellulose ingredients. Concentrated isopropyl alcohol (91%), is used to extract the ASA from the insoluble inactive ingredients. (Laboratory 100% isopropyl alcohol may be substituted for the...