Synthesis Of Aspirin Synthesis Essay

Organic Chemistry Laboratory – CH 200 (2014-2015) Experiment 9

Synthesis of Aspirin through Esterification and Crystallization

Justin Gaña, Jamilette Guiam, Angelica Jimenez, and Joanna Jusay*

Department of Biological Sciences, College of Science

University of Santo Tomas, España Street, Manila 1051

Date Submitted: November 7, 2014

Abstract The synthesis of aspirin was remodeled and revised for a small scale experiment. An esterification reaction from the combination of salicylic acid and acetic anhydride with the presence of an acid catalyst produced acetylsalicylic acid (aspirin) and acetate. Purification of the crude aspirin was done through a technique called crystallization, wherein both the single solvent and mixed solvent

4.00 mL of acetic anhydride was then added to the salicylic acid inside the Erlenmeyer flask. 5 drops of concentrated sulfuric acid (H2SO4) was added to the cloudy solution. Concentrated sulfuric acid acted as a catalytic agent which sped up the reaction. Prior to weighing and preparing the solution, a water bath was placed on top of a hot plate and allowed to heat up until only 80 °C. An increase in temperature would cause the solution to polymerize into a different substance. Once the desired temperature of the water bath was achieved, the Erlenmeyer flask containing the solution was floated in it and swirled until the salicylic acid dissolved and the solution became clear. Ten minutes was the maximum allotted amount of time for the reaction. After the dissolution of the salicylic acid and acetic anhydride, 20 mL of distilled ice water was added to the solution and was subjected to an ice bath. The water would destroy any unreacted acetic anhydride and will cause the insoluble aspirin to precipitate (Bettleheim, 2001). The flask was swirled to initiate and speed up the crystallization of acetylsalicylic acid and to allow the oily layer to disperse. Once the oily layer disappeared, Buchner funnel was prepared. The funnel was placed on top of an Erlenmeyer flask subjected to vacuum suction. The purpose of the vacuum suction was to dry the crystals as much

The hydroxyl group on the benzene ring reacts with the acetic anhydride to form an ester functional group. This reaction is called an esterification reaction (Pavia, Lampman, Kriz, & Engel, 1999). A similar reaction was executed using isoamyl alcohol and acetic anhydride. The addition of sulfuric acid catalyzes the reaction. When the reaction is complete, there will be some unreacted salicylic acid and acetic anhydride that will be left with the crude aspirin. A technique used to purify the aspirin is called crystallization. It is so called because it involves dissolving a solid that has originally crystallized from a reaction or mixture, and then causing it to again crystallize from another solution. The typical setup for this is that the crude solid is dissolved in a hot suitable recrystallization solvent. The solution allowed to cool down and crystallization to happen (Lehman,