a student dissolves 80 mg of a crude product in 4.5 mL( the minimum required) of methanol at 25 deg C . She cools the solution in an ice bath and obtains crystals. The crystals are recovered by filtration and rinsed with 0.5 mL of ice-cold methanol. After drying, the weight of the crystals is 5 mg. Why was the recovery so poor? what could she do to improve the process?
chemistry - DrBob222, Monday, February 11, 2013 at 8:27pm
Try a new solvent.
chemistry - sara, Monday, February 11, 2013 at 8:37pm
how would that help trying a new solvent? i don't understand why the recovery would be so poor, do you know?
chemistry - DrBob222, Monday, February 11, 2013 at 9:28pm
The solubility in methanol at 25 C and at 0C may be close to the same value. I would try a new solvent OR use a different temperature range. Methanol is a polar solvent; a non-polar one might be better. One of the main things in recrystallization is to find a solvent where the solubility at higher T values is high and the solubility at low T values is low.