Methyl Salicylate synthesis

Synthesize Methyl Salicylate

1. Transfer about 60 mL of methanol to the 125 mL Erlenmeyer flask. Add 13.00 g of aspirin to the flask and swirl  until the tablets dissolve. (Aspirin tablets may contain binders that do not dissolve in methanol, which is no cause for concern.)

2. Add about 10.0 mL of concentrated sulfuric acid to the reaction vessel and swirl to mix the solutions. Be careful to add the acid slowly to avoid boiling the solution and causing some of the acidic solution to sputter out of the flask.

3. Clamp the flask to a ring stand and partially immerse it in a hot water bath at about 60°C.

4. Allow the reaction to proceed, stirring the reaction mixture occasionally, for 60 minutes. As the methyl salicylate forms, you’ll notice a distinct wintergreen odor. Keep the reaction mixture at about 60°C, adding water to the bath if necessary to keep its level up. The level of the liquid in the reaction vessel will decrease as methanol evaporates from the flask. Add more methanol as needed to keep the reaction vessel near its original volume.

5. After 60 minutes, stop adding methanol to the flask. Increase the heat slightly to being the liquid in the reaction flask to a gentle boil. Boil the solution long enough to vaporize most of the remaining methanol.

6. When enough methanol has boiled off to reduce the volume in the reaction vessel to about half its original volume, remove the flask from the water bath and set aside to cool.

Part II: Isolate and Purify the Product

The brown liquid in the reaction vessel is a complex solution that contains methanol, crude methyl salicylate, sulfuric acid, unreacted aspirin, and other impurities. Methyl salicylate is freely soluble in methanol, but only very slightly soluble in water. We’ll take advantage of that differential solubility to extract most of the water-soluble impurities from the crude product.

1. Pour the contents of the reaction flask into the sep funnel.

2. Add about 50 mL of ice cold tap water to the sep funnel, cap the funnel, and agitate the contents vigorously for 30 seconds.

3. Allow the contents of the sep funnel to separate into two layers. The aqueous layer contains nearly all of the sulfuric acid and most of any other water-soluble impurities. (Make sure you know which layer is which.) Separate the two layers, and transfer the aqueous layer to the 250 mL beaker.

4. Do a second washing by repeating steps 3 and 4.