Aspirin Synthesis Materials:
2.0 g salicylic acid
5 mL acetic anhydride
Concentrated sulfuric acid
Cold distilled water
Hot distilled water
100 mL conical flask
Suction filtration setup
Vacuum pump with retort stand
Measuring cylinders (10 mL and 50 mL)
1. Use a top-pan balance to weigh approximately 2.0g of salicylic acid added into a tared dry 100mL conical flask. Record the actual weight.
2. Using the fume hood, add in 5 mL of acetic anhydride to the flask with salicylic acid
3. Add 3-4 drops of concentrated sulphuric acid. Swirl to mix the solution.
4. To complete the reaction, use a water bath to heat the mixture for 15 mins
5. Remove flask from the water bath and continuously add in 1 mL of cold water dropwise, while it’s still hot. Swirl the flask when doing so. Quickly, add in 20 mL of cold water. With a stirring rod, immediately stir and rub the inner walls of the conical flask for 5 mins. Immerse it into an ice-bath for an additional 5 minutes to induce crystallisation.
6. Use 2 pieces of filter paper for suction filtration in order to collect the crude product. Use a small amount of cold water to wash it. Transfer the crude product into a new 100 mL conical flask.
(II) Purification of Aspirin
7. Add in approximately 5 mL of ethanol in order to dissolve the crude product, forming a hot saturated solution. If necessary, warm it by using a hot plate. Do not let it boil.
8. Add approximately 30 mL of distilled water into the solution once the solid has been dissolved. Heat it on a hotplate. If the solid can be seen, add in 1 mL of ethanol and warm gently until the solid dissolves completely. (solid should be completely clear)
9. Let solution to cool down till room temperature, followed by placing it in the ice-bath in the fume hood (around 10-15 mins). While cooling, do not agitate the mixture.
10. Record the weight of a clean, dry watch glass together with two pieces of filter paper
11. Use the weighted filter paper to acquire recrystallize product by suction filtration
12. Move the crystals and filter paper onto the weighted watch glass. Dry them in the oven (100?) for 15-20 mins.
13. Place the watch glass that contains filter paper and crystals in the desiccator for 5-10 mins.
14. Write down the weight of the dried crystals together with the filter paper and watch glass.
15. Calculate the weight and the percentage yield of the dried crystals