Synthesis Aspirin

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Synthesis Aspirin

1. Assemble the apparatus provided for heating under reflux, with the flask in a water bath. Make sure that the inside of the flask and condenser are both dry.

2. Using a measuring cylinder, add 4 cm3 of ethanoic anhydride to the flask, followed by five drops of concentrated phosphoric acid and a few anti-bumping beads. Swirl the flask carefully to mix the reagents. Reassemble the apparatus and switch on the water through the condenser.

3. Heat the water bath until the solid dissolves. Then continue to heat with the water in the water bath just boiling for a further five minutes.

4. Switch off the Bunsen and then carefully add 2 cm3 of water down the condenser. The water hydrolyzes the unreacted ethanoic anhydride in the flask and may cause the mixture in the flask to boil.

5. When the vigorous reaction in the flask has ended, pour the mixture into about40 cm3 of cold water in a small beaker. Stir the mixture in the beaker. At this point, solid aspirin should form, but further stirring and rubbing the inside of the beaker with the glass rod may be necessary to induce crystallization.  Allow the beaker to stand in an ice bath to complete crystallization.

6. Filter off the aspirin by suction filtration using a Buchner funnel and flask. Rinse the beaker with distilled water and pour the rinsing into the funnel. Dry the solid as much as possible in the Buchner funnel.

7. Add small portions of water to the flask and heat the flask with the Bunsen Burner until the solid dissolves.

8. Cool the flask in an ice-bath so that crystals will form. Filter off the crystals by suction filtration, attempting to dry them as much as possible. Transfer the crystals to a piece of filter paper and allow them to dry overnight. In the space provided.