Question

i need to recrystallize 1,4-dichlorobenzene (started with 1:1 mix of 1,4-dichlorobenzene and 4-aminobenzoate then dissolved in diethyl ether and separated by adding HCl). the solvents I have available are 99% ethanol, methanol, water, sodium hydroxide, and sodium sulfate)
Do I need to dry the product with sodium sulfate and the rotovap before recrystallizing? and what solvent(s) would work to recrystallize after rotovap?

Answer 1

1,4-Dichlorobenzene will be in dietyl ether (organic) layer, 4-aminobenzoate will form a salt and will go into water layer after extracting the mixture of compound with ether,water after adding HCl.. The organic layer should be dried over sodium sulfate to remove the traces of water present.

After drying on sodium sulfate, solvent should removed on rotovap, or by placing the beaker on hot water bath, because in extraction we will use large amount of solvent. (For recrystallization generally saturated solutions are preferred).

Once the solvent is removed you will be left with solid 1,4-dichlorobenzene.

Take the solid in a beaker, dissolve it in etanol and heat it.

Filter the hot solution and cool it to room temperature, you will see the crystals forming slowly.

If crystals are not forming then heat it once again and heat it, to the hot ethanolic solution add few drops of boing/hot water, at this point it will become cloudy. To this cloudy solution add some more hot ethanol till the cloudiness disappears. Cool the solution to room temperature, at this point crystals should start forming/appearing.