Question

The lab experiment is the synthesis of aspirin. The product will be acetylsalicylic acid (aspirin) and the by-product will be acetic acid. How will you separate the by-product from the desired product? is it from recrystallization and then vacuum filtration?

Answer 1

Yes you can do recrystalization to separate the mixture.

Recrystalization of Aspirin

Dissolve the impure aspirin in 15 ml of ethyl alcohol, in a 150 ml beaker, then warm on a hot plate and pour into the solution 25 ml of warm water. If a solid separates at this point, continue warming until solution is transparent, then cover the beaker with a watch glass and set aside to cool slowly. Note, if warming the water/alcohol/aspirin mixture does not form a solution, add more alcohol in 5 ml increments until the mixture is transparent. After crystals form, collect the crystals using vacuum filtering. Wash the collected crystals with ice water and then test for salicylic acid and acetic acid.This is done for checking whether any amount of impurities is remaining. If so, do recrystalization one more time.Weigh and determine the melting point of the pure aspirin. Confirm the purity of aspirin with NMR.