SYNTHESIZING ASPIRIN

Editor's Note:

Acetylsalicylic acid, most likely more familiar to you under the name "Aspirin" is a common over-the-counter pharmaceutical used as a pain reliever. The equation for synthesizing aspirin is relatively simple: combine salicylic acid with acetic anhydride in the presence of a catalyst like phosphoric acid, and acetylsalicylic acid is produced alongside an acetic acid waste product. On paper, the synthesis looks like this:

It looks simple enough, right? But like most chemical reactions, there are several obstacles in taking this reaction from the page to an industrial process. There are several of tricky things hidden in the equation above. First of all, this forward reaction can also occur in the reverse direction. Heat your reaction too high, and your acetylsalicylic acid and acetic acid will form back into salicylic acid and acetic anhydride. Additionally, in order to have etible