Lisa Barton CHEM 2312 Organic Chemistry Performed: 2/4/12. Synthesis of Aspirin

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Horace Edwards
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1 Lisa Barton CHEM 2312 rganic Chemistry Performed: 2/4/12 Synthesis of Aspirin

2 bjective: The goal of this experiment is to synthesize Aspirin (Acetylsalicylic Acid) from the reaction of Salicylic acid and Acetic Anhydride. Reaction Equations: + H3P4 Salicylic acid Acetic Anhydride Acetylsalicylic Acid MW: g/mol MW: g/mol MW: g/mol MP: 159 C BP: 140 C MP: C Mechanism: H H

3 Theoretical Yield: Before the theoretical yield can be calculated, first the limiting agent must be found. In order to find the limiting reagent, the number of moles of each reagent must be found; because the reaction occurs in a 1:1 ratio, the reagent with the smaller number of moles is the limiting reagent. In this reaction, either the salicylic acid or the acetic anhydride is the limiting reagent. Salicylic acid: 0.999g x 1 mol = moles g Acetic Anhydride: 2.0mL x 1.08g x 1mol 1mL g = moles Because Salicylic acid produces the smaller amount of moles, it is the limiting reagent. Also, Salicylic acid and Acetylsalicylic Acid occur in a 1:1 ratio, so the number of moles produced by salicylic acid is equal to the number of moles produced by acetylsalicylic acid. Therefore, the theoretical yield of acetylsalicylic acid can be calculated: Acetylsalicylic acid: mol x g = grams. 1mol Procedure: To begin this experiment, first grams of salicylic acid was placed in a test tube. Next, 2.0 ml of acetic anhydride was added to the same test tube. For this reaction, the acetic anhydride acts as both the solvent and the reagent. 5 drops of concentrated sulfuric acid was then added to the test tube. The mixture was then thoroughly stirred with a glass rod. A 50 ml beaker was subsequently filled with ml of water and than heated on a hot plate to be used as a hot water bath. The test tube containing the

4 reaction mixture was than heated in the hot water bath and stirred until the solids in the test tube dissolved. nce the solids had fully dissolved, the contents of the test tube were poured into a 20 ml beaker containing 15 ml of water. This mixture was than mixed thoroughly and cooled on ice. nce cooled, the resulting crystals were collected via vacuum filtration in a Hirsch funnel. This collected product was than placed into a new test tube and recrystallized in water (hot water was added until the product dissolved and then cooled on ice). This purified product was then collected, weighed out and the yield was calculated. Finally, the melting point was determined to assess whether or not aspirin was the final product. bservations: The protocol called for 1.0 grams of salicylic acid to be measured out, however only grams was used. When the concentrated sulfuric acid was added to the reaction mixture, it created a bad smell and it also caused the mixture to heat up. This mixture of salicylic acid, acetic anhydride and sulfuric acid was white in color. When it was heated in the hot water bath, most of the solid dissolved with only a very little amount remaining in its solid state. After the contents of the original test tube were poured into 15 ml of water and cooled, white crystals formed. These were than filtered out and a very large portion of product was collected. riginally, the entire product was placed in one test tube and hot water was used to attempt to dissolve the product. However, because there was so much of the product, the test tube was not large enough to fully dissolve the product. Therefore, the product was recollected using the Hirsh funnel and then divided into two test tubes to be dissolved again by hot water. It also took a very

5 long time and a lot of heat to finally re-dissolve the product. Most of the contents of the test tubes were poured out to be vacuum filtered, however a small amount of product did remain in the test tubes and could not be removed. When the final product was weighed out, it had a mass of grams. The melting point was also observed to be within the range of C. Characterization: The percent yield of an experiment is equal to the mass of the actual yield divided by the mass of the theoretical yield multiplied by 100. Therefore, this formula can be applied to calculate the percent yield of this experiment: % yield of Acetylsalicylic Acid (Aspirin) = 0.543g x 100 = 41.7% 1.302g The melting point of the final product that was collected was found to be within the range of C. This melting point range does fall within the expected melting point range of acetylsalicylic acid, which is C. This implies that the final product collected from this experiment was in fact aspirin. Conclusion: The results of this experiment did reflect what was originally expected to occur. The established melting point of acetylsalicylic acid (aspirin) is within the range of C. The melting point of the experimental product was found to be within the range of C. These two ranges do overlap, which implies that the final product is in fact aspirin. The percent yield was low, less than half the theoretical yield, which could have

6 been caused by several different things. To start, some of the product was left behind in the test tube when the product was vacuum filtered, which would cause a decrease in the percent yield. Also, when the product would not dissolve in hot water in a single test tube and had to be re-filtered and divided into two test tubes, because it was being transferred so many times so of the product could have been lost during these steps which would also have caused a lowering in the percent yield.

ORG1 Syntheses of Acetaminophen and Aspirin

ORG1 Syntheses of Acetaminophen and Aspirin RG1 Syntheses of Acetaminophen and Aspirin Estimated Time Required: 60 minutes Introduction Ethanoylation (better known as acetylation) is the introduction of an acetyl functional group onto a suitable