Chemistry Lab Report: Preparation of Aspirin (Acetyl Salicylic Acid) Title: Preparation of Aspirin (Acetyl Salicylic Acid) Objective: To synthesize acetylsalicylic acid (aspirin) from salicylic acid and acetic acid, determine the melting point of the synthesized product, and calculate the percentage yield of the reaction. Introduction: Aspirin, chemically known as acetylsalicylic acid, is a widely used medication for pain relief, fever reduction, and anti-inflammatory purposes. It is typically synthesized through an esterification reaction where the hydroxyl group of salicylic acid reacts with an acetylating agent. In this experiment, salicylic acid reacts with acetic acid in the presence of an acid catalyst to form acetylsalicylic acid and water. Materials: Salicylic acid (1.5 g) Acetic acid (6 mL) 85% sulfuric acid or phosphoric acid (catalyst) Distilled water (20 mL) Conical flask Water bath Ice bath Filter apparatus (e.g., Büchner funnel, filter paper) Heating plate Procedure: 1. Place 1.5 g of salicylic acid into a clean conical flask. 2. Add 6 mL of acetic acid to the flask. 3. Carefully add a few drops of 85% sulfuric acid or phosphoric acid as a catalyst. 4. Heat the mixture in a water bath at 90°C for 3 minutes. 5. Remove the flask from the water bath and allow it to stand until it is still hot. 6. Add 20 mL of distilled water to the flask and allow it to stand until crystallization begins. 7. Cool the flask in an ice bath to maximize the yield of crystals. 8. Filter the crude aspirin crystals using a suitable filtration method. 9. Recrystallize the crude product from hot water to purify it. 10. Dry the purified aspirin crystals. 11. Determine the melting point of the recrystallized aspirin. 12. Weigh the final purified product to calculate the percentage yield. Reaction Equation: The reaction between salicylic acid and acetic acid to form acetylsalicylic acid (aspirin) is an esterification reaction: $$ \text{HOC}_6\text{H}_4\text{COOH} \text{ (Salicylic Acid)} + \text{CH}_3\text{COOH} \text{ (Acetic Acid)} \xrightarrow{\text{H}_2\text{SO}_4/\text{H}_3\text{PO}_4} \text{CH}_3\text{COOC}_6\text{H}_4\text{COOH} \text{ (Acetylsalicylic Acid)} + \text{H}_2\text{O} \text{ (Water)} $$ Data and Observations: Mass of salicylic acid used: 1.5 g Volume of acetic acid used: 6 mL Initial observations (e.g., appearance of reactants): [Record observations]* Observations during heating (e.g., dissolution, color changes): [Record observations]* Observations during cooling and crystallization (e.g., crystal formation): [Record observations]* Mass of crude aspirin obtained: [Record value] g* Mass of recrystallized aspirin obtained: [Record value] g* Melting point of recrystallized aspirin: [Record value] °C* Calculations: 1. Molar mass of salicylic acid ($\text{C}_7\text{H}_6\text{O}_3$): $$ (7 \times 12.01) + (6 \times 1.01) + (3 \times 16.00) = 138.13 \text{ g/mol} $$ 2. Moles of salicylic acid: $$ \text{Moles} = \frac{1.5 \text{ g}}{138.13 \text{ g/mol}} = 0.01086 \text{ mol} $$ 3. Molar mass of acetylsalicylic acid ($\text{C}_9\text{H}_8\text{O}_4$): $$ (9 \times 12.01) + (8 \times 1.01) + (4 \times 16.00) = 180.17 \text{ g/mol} $$ 4. Theoretical yield of aspirin: (Based on 1:1 stoichiometry with salicylic acid as limiting reactant) $$ \text{Theoretical yield} = 0.01086 \text{ mol} \times 180.17 \text{ g/mol} = 1.956 \text{ g} $$ 5. Percentage Yield: $$ \text{Percentage Yield} = \frac{\text{Actual mass of recrystallized aspirin}}{\text{Theoretical yield}} \times 100\% $$ $$ \text{Percentage Yield} = \frac{\text{[Record actual mass]} \text{ g}}{1.956 \text{ g}} \times 100\% = \boxed{\text{[Calculate value]} \%} $$ Results: The theoretical yield of aspirin from 1.5 g of salicylic acid was calculated to be 1.956 g. The actual mass of purified aspirin obtained was [Record value] g. The percentage yield of the synthesis was [Calculate value] %. The melting point of the synthesized aspirin was determined to be [Record value] °C. (The literature melting point for pure aspirin is 135-136 °C). Discussion and Conclusion: The experiment successfully synthesized aspirin from salicylic acid and acetic acid. The calculated percentage yield reflects the efficiency of the reaction and purification steps. A melting point close to the literature value of 135-136 °C indicates a high purity of the synthesized product. Any discrepancies in the melting point or a lower-than-expected percentage yield could be attributed to factors such as incomplete reaction, loss of product during filtration or transfer, or the presence of impurities. 3 done, 2 left today. You're making progress.