Question

An experiment performed using solid to liquid extraction, liquid-liquid extraction, heating, and recrystallization to isolate caffeine, was not totally successful due to their being very little to no product of caffeine left when the time came to recrystallize the pure caffeine. During the experiment what could of caused there to be not enough caffeine to recrystallize it? ethyl acetate was used as the organic solvent hexane and acetone was used to recrystallize the crude caffeine, through mixture and boiling. Could boiling to fast have an effect on why there was not enough crystals for me to recrystallize in a vacuum hirsch funnel?

Answer 1

The experiment might not have been successful due to the solvent used for recrystallisation. Caffeine is completely soluble in acetone. However if acetone is added too much the precipitate or the recrystallised caffeine would not be formed and hence would not reach the cloud point (a stage where caffeine just starts to precipitate). The second thing that shows ineffective results could have been excess addition of hexane. Hexane is to be added carefully dropwise until cloudiness is just seen. Excess of hexane can prevent recrystallisation effectively. In both the above cases, boil the solution slightly and carefully so that the excess boils off and proper results are obtained.