Question

In a lab, we seperated Excedrin (paracetamol, acetylsalicylic acid, caffeine, and binder). First we dissolved the powder in diethyl ether. This seperated the mixture into caffeine/acetylsalicylc acid and binder/paracetamol. We dissolved the binder/paracetamol in acetone to seperate it. WHY was acetone used? Thanks!

Answer 1

Binder in the painkilling tablet is generally used for binding all the components together. They are polymers such as cellulose, starch, and silica gel. These polymers are insoluble in acetone.
Whereas, paracetamol is soluble in acetone.

Thus, after separation of caffeine, acetylsalicylic acid, from binder and paracetamol. To separate binder from paracetamol, we use the above characteristics of solubility. When we add a mixture of binder and paracetamol to the acetone, paracetamol gets dissolved into acetone leaving behind binder undissolved. Which we can separate by simple filtration. After filtration acetone is distilled or evaporated in rotavap to get paracetamol. Which is further recrystallized to get pure paracetamol.