Aspirin Synthesis Lab Report PDF

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Ansley Morgan Chem 3021-001 March 30, 2019 Aspirin Synthesis Abstract Aspirin synthesis reactions are done in two steps, saponification and esterification. The procedure involved reacting methyl salicylate with sodium hydroxide and sulfuric acid to create salicylic acid. The percent yield for this step was 82.6%. The second step involved combining the created salicylic acid with acetic anhydride and phosphoric acid to create the final desired product of acetyl salicylic acid, also known as aspirin. The percent yield for this step was 51%. NMR and IR analysis confirmed the final product production. Introduction Although seemingly complicated the aspirin synthesis reaction is actually quite simple. It is broken down into two smaller reaction, saponification and esterification. Saponification reactions have been performed for thousands of years due to their ability to create soap.1 These reactions are also quite simple, but can have very desirable products.2 Although, mostly commonly these reactions are used to produce soaps they have ventured into some cleaning products, and serve as the main way to create glycerol. In this experiment this process was used to create salicylic acid from methyl salicylate. Once this was complete, the process of esterification began. This type of reaction is one of the most important in organic synthesis due to the significance of its products.3 These reactions simply result in the production of an ester, but these esters are useful in many different aspects of life.4 Esterification reactions happen in other places outside of research labs, they are prevalent in several biological processes and electronic materials.5 The goal of the experiments was to combine these two reactions to result in the synthesis of aspirin from methyl salicylate. Discussion To start this experiment 0.5 mL of methyl salicylate was combined with 4.0 mL of 6M NaOH and boiled for 30 minutes. That solution was then allowed to cool to room temperature. Once cooled 5.0 mL of 8M sulfuric acid was added, and a white precipitate was formed. It was then cooled on ice, and the precipitate was filtered on a Hirsch funnel while being washed with cold water. The precipitate was recrystallized in a large test tube containing 10mL of water. The resulting crystals were filtered using a Hirsch funnel. The product weighed 0.433 g, and by dividing the products weight by the theoretical yield the percent yield was calculated to be 82.6%. A melting point was taken and determined to be 157 degrees Celsius. The desired product of salicylic acid was confirmed by IR analysis and comparing melting points. Once salicylic acid was created 3 equivalents, 0.89 mL, of acetic anhydride was added, and was stirred. A drop of phosphoric acid was then added, and the resulting solution was stirred and heated on a water bath to 90 degrees Celsius. After 20 minutes of heating and stirring, the solution was removed from heat, and 2 mL of water was added. Once the solution cooled another 2 mL of water was added, and crystals began to form. The crystals were filtered using Hirsch funnel filtration while washing with cold water. The product was then recrystallized from water. The resulting crystals weighed 0.285g, and by dividing the products weight by the theoretical

yield the percent yield was calculated to be 51%. A melting point was taken and determined to be 133 degrees Celsius which is very close to the expected melting point of 135 degrees Celsius. The created of the desired product, acetyl salicylic acid, was confirmed using NMR analysis. The mechanisms for the reactions can be found below. Reagents Methyl Salicylate

Melting Point Boiling Point -9 degrees 220 degrees Celsius Celsius

Molar Mass 152.149 g/mol

Density 1.174 g/mL

Sodium Hydroxide

318 degrees Celsius

1388 degrees Celsius

40 g/mol

2.13 g/mL

Sulfuric Acid

10 degrees Celsius

337 degrees Celsius

98.1 g/mol

1.84 g/mL

Salicylic Acid

158.6 degrees 211 degrees Celsius Celsius

138.1 g/mol

1.44 g/mL

Acetic Anhydride

-73.1 degrees Celsius

102.1 g/mol

1.08 g/mL

Phosphoric Acid

42.35 degrees 159 degrees Celsius Celsius

98 g/mol

1.88 g/mL

Acetyl Salicylic Acid

135 degrees Celsius

180.12 g/mol

1.4 g/mL

140 degrees Celsius

140 degrees Celsius

Theoretical Yield Calculations Part 1: Methyl Salicylate 0.5mL (1.17g/mL)= 0.585g 0.585g (1 mol/152.15g) = 0.0038 mol Sodium Hydroxide 4mL (1L/1000mL)(6 mol/1L)= 0.024 mol Salicylic Acid 0.0038 (138g/1 mol)= 0.5244 g Yield (0.433g/0.5244g)100= 82.6% Part 2: Salicylic Acid 0.433g (1 mol/138g)= 0.0031 mol Acetic Anhydride 0.89mL(1.08g/1 mL)(1 mol/102 g)=0.0094 mol Aspirin 0.0031 mol (180g/1 mol)= 0.558 g Yield (0.285g/0.558g)100= 51% Experimental In this experiment a reaction involving methyl salicylate was performed and resulted in the production of salicylic acid. The salicylic acid was then used in a reaction to synthesize acetyl salicylic acid, aspirin. In the first week 0.5 mL of methyl salicylate was combined with 4.0 mL of 6M NaOH and boiled for 30 minutes. That solution was then allowed to cool to room temperature. Once cooled 5.0 mL of 8M sulfuric acid was added, and a white precipitate was formed. It was then cooled on ice, and the precipitate was filtered on a Hirsch funnel while being washed with cold water. The precipitate was recrystallized in a large test tube containing 10mL of water. The resulting crystals were filtered using a Hirsch funnel. The desired product of salicylic acid was confirmed by the IR shown below. Using the salicylic acid created in the first week, the second week started with adding 3 equivalents, 0.89 mL, of acetic anhydride and stirring. A drop of phosphoric acid was then added, and the resulting solution was stirred and heated on a water bath to 90 degrees Celsius. After 20 minutes of heating and stirring, the solution was removed from heat, and 2 mL of water was added. Once the solution cooled another 2 mL of water was added, and crystals began to form. The crystals were filtered using Hirsch funnel filtration while washing with cold water. The product was then recrystallized from water. The created of the desired product, acetyl salicylic acid, was confirmed by the IR and NMR shown below. NMR analysis shows 2.35 (s,3H), 7.14 (t,1H), 7.4 (t,1H), 7.6 (t,1H), 8.1 (t,1H).

Conclusion In conclusion this experiment involved synthesizing aspiring from methyl salicylate. The combination of methyl salicylate, sodium hydroxide, and sulfuric acid resulted in a white precipitate. The precipitate formed turned out to be salicylic acid that was then reacted with acetic anhydride and phosphoric acid to form the desired end product of acetyl salicylic acid. Throughout the experiment melting points were taken and IRs were run in order to confirm that the desired products were indeed being produced. By using NMR analysis of the final product, we were able to confirm that aspirin was synthesized. References 1. Témoin‐Fardini, S.; Servant, J.; Sellam, S. New test method for the evaluation of the preservation efficacy of soaps at very alkaline pH made by saponification. International Journal of Cosmetic Science online. (2017). 2. Yang, S.; Yoo, S.; Lee, J.; Kim, J.; Yeum, J. Surface Properties of a Novel Poly (vinyl alcohol) Film Prepared by Heterogeneous Saponification of Poly (vinyl acetate) Film. Polymers online. (2017).

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