Which solvent is most suitable for recrystallizing acetanilide? Is it water, methanol or hexane? Why?

Question

Which solvent is most suitable for recrystallizing acetanilide? Is it water, methanol or hexane? Why?

Answer 1

The premise behind purifying by recrystallisation is you want to select a solvent that your compound is soluble in only when heated and the impurities are soluble in at all temperatures, so that as the solvent cools, the compound of interest comes out of solution and can be recovered through filtration.  You also need to make sure that the boiling point of the solvent is lower than the melting point of the compound as it wouldn't be good if your compound of interest melted as you were trying to get it into solution.  Acetanilide is soluble in hot water only so this would probably be the best solvent to use.  Looking at structures, acetanilide is more neutral-nonpolar in polarity so water would be good, especially as any polar contaminants will remain in  solution on cooling.