aspirin-procedure

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The chemical equation for the reaction is as follows: C7H6O3 + C4H6O3 ---> C9H8O4 + C2H4O2 This equation indicates a 1:1:1:1 stoichiometric ratio.
 * Calculation of the Limiting Reactant of the reaction to synthesize aspirin: **

We used 1.01 grams salicylic acid (C7H6O3) and 2.5 mL acetic anhydride (C4H6O3). Molar mass salicylic acid = 138.1 g/mol Molar mass acetic anhydride = 102.1 g/mol

1.01 grams salicylic acid * (1 mol / 138.1 grams) = 0.0073 mol acid in reaction

Density of acetic anhydride = 1.082 g/cc = 1.082 g/mL Density = mass / volume 1.082 g/mL = mass / 2.5 mL mass = 2.705 grams acetic anhydride

2.705 grams acetic anhydride * (1 mol / 102.1 grams) = 0.0265 mol acetic anhydride in reaction.

Based on the molar ratios of the two reactants, we have an excess of acetic anhydride, so the __ salicylic acid is the limiting reactant. __

// Reaction // 1. Measure 1.0 grams (Group 1 used 1.01 grams, Group 2 used 1.05 grams) salicylic acid, place in an Erlenmeyer flask, and add 2.5 mL acetic anhydride. Swirl the flask to wet all of the acid crystals. 2. Add 3 drops concentrated H2SO4 to the mixture and heat the flask in a boiling water bath for 10 minutes. 3. Remove the flask from the hot water bath and add 5 mL DI ice water to decompose any remaining acetic anhydride. Put solution on an ice bath until crystallized aspirin is no longer forming. Stir occasionally. If an oil appears, reheat the flask until the oil disappears and try cooling again. 4. Transfer crystals to a vacuum filtration system using iced DI water to rinse the crystals and pour slowly onto the filter paper. Dry as best as possible. // Recrystallization and Analysis // 1. The salicylic acid impurity needs to be removed via recrystallization. 2. Place the aspirin crystals in a 50 mL beaker and add 4 mL ethanol and 12 mL water. Warm this mixture in a 60 degree water bath until the aspirin dissolves. 3. Cover the beaker with a watch glass and remove it from heat. Allow it to cool slowly, and then put the beaker in an ice bath. 4. Use vacuum filtration to again collect the crystals. Wash them with two 5-mL volumes of ice water. Dry the aspirin or wait until next lab period. 5. Take the mass of the aspirin crystals. 6. Measure the melting point of the purified aspirin. 7. Verify the compound's purity using IR and NMR.
 * Procedure: **