The Drug War

Reaction

1. Obtain an appropriate heat source and assemble an apparatus for heating under reflux consisting of an air condenser attached to a conical reaction vial of appropriate size.

2. Measure 2.00 mmol of methyl salicylate into the reaction vial; then add 2.5 mL of aqueous 6 M sodium hydroxide and a boiling chip or two

3. Heat the reaction mixture under gentle reflux for 30 minutes, measuring from the time the solution starts to boil

4. Be sure that the reflux ring of condensing vapor remains at least 2 cm below the top of the condenser

5. If its level goes higher than this, reduce the heating rate

6. If after 30 minutes under reflux the reaction mixture is cloudy or contains an oily upper layer continue heating under reflux until the cloudiness or (oil) disappears and the reaction mixture no longer smells like wintergreen.

7. When the reaction is complete, remove the condenser as soon as it is cool enough to handle; otherwise the joints might freeze.

8. Remove the boiling chips and transfer the reaction mixture to a beaker larger enough to contain it and the sulfuric acid to be added

9. Slowly add 2.7 mL of 3 M sulfuric acid while stirring, and test the pH of the supernatant liquid (liquid near the surface) using your stirring rod and a strip of pH paper.

10. If the pH is above 2, add enough additional sulfuric acid drop by drop to bring it down to 2

11. Cool the mixture in an ice/water bath for five minutes or more

Separation

1. Collect the salicylic acid by vacuum filtration and wash it on the filter with ice cold water

Purification and analysis

1. Purify the salicylic acid by recrystallization from boiling water.

2. There should be no need to filter the hot solution

3. Collect the product by vacuum filtration and wash it with a little ice cold water

4. Dry the product to constant mass and measure its mass

5. Measure the melting point of the dry product and of a 1:1 mixture of the product with salicylic acid synthesized from benzene

6. In your report include calculations of the theoretical yield of product (based on the actual mass of your reactant) and the percent yield of your preparation,

7. Try to account for any significant material losses (see exercise 4) and discuss the results of the mixed melting point analysis.

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