I have prepared a chemical compound and I need to do recrystalyzation for purification, I tried many solvents like dust. water, benzene, chloroform, ethanol, cyclohexan...
It is soluble in all above on cold, how can I do recrystalyzation
Hello, there are certain rules which you shuld fulfill for good recrystallization. The choice of solvent is perhaps the most critical step in the process of since the correct solvent must be selected to form a product of high purity and in good recovery or yield. Consequently a solvent should satisfy certain criteria for use in recrystallization:
a. The desired compound should be reasonably soluble in the hot solvent, about 5 g/100 mL (5 mg/100 μL) being satisfactory, and insoluble or nearly insoluble in the cold solvent. Note that the reference temperature for determination of the solubility in "cold" solvent is often taken to be room temperature. This combination of solute and solvent will allow dissolution to occur in an amount of solvent that is not unduly large and will also permit recovery of the purified product in high yield. A solvent having this type of solubility properties as a function of temperature would be said to have a favorable temperature coefficient for the desired solute.
b.Conversely, the impurities should either be insoluble in the solvent at all temperatures or must remain at least moderately soluble in the cold solvent. In other words, if the impurities are soluble, the temperature coefficient for them must be unfavorable; otherwise the desired product and the impurities would both crystallize simultaneously from solution.
c. The boiling point of the solvent should be low enough so that it can readily be removed from the crystals. d. The boiling point of the solvent should generally be lower than the melting point of the solid being purified.
e. The solvent should not react chemically with the substance being purified.
for more info please see attached paper.
Good luck!
If you want to purify by recristallization and it don't work, you can purify by other means, eg, chromatography. you still can get crystals if you evaporate the solvent slowly. Choose a solvent of low boiling point, best regards
Did you try DCM:hexan mix. First try to get pure compound with column chromatography. After purification try DCM:h exam mix
- Badges
- Science method