I have performed a reaction in DMSO and I removed it with lyophillization. I want to find a suitable solvent to recrystallize my compound, which is as I predicted mid-polar, but I'm afraid some of my by-products are mid-polar as well. Any thoughts on how should I handle the technique and which solvent/ solvent mixtures I can use?
Thank you!
What is your crude purity? If there are substantial amounts of byproducts this can be difficult. Also, residual DMSO can be a problem. I would suggest dissolving in organic and extracting with water first.
When you have evaporated again, you have two options, just like chromatography, normal mode where the anti solvent is less polar than the solvent and reverse mode, where the anti solvent is more polar (and often water). For normal mode, a good place to start is your TLC mobile phase with the more polar component as the solvent, dissolve in as little volume as possible. Heating gently is often useful. When dissolved add the less polar as the antisolvent (or hexane/heptane which works with most organic solvents). You will have a good chance of it working if you notice cloudiness around the antisolvent as you add.
If everything dissolves quickly or in a small amount of solvent, change the solvent to less polar. If it doesn't dissolve at all, try adding 10% of a more polar solvent. If still not dissolving, evaporate and try a more polar solvent.
A lot can go wrong in this, so you will need to be patient and experiment, but the rewards of a beautiful crystal are worth it.
Lyophillization usually used to remove water and perhaps low-boiling point organic solvents if they are present in your sample; I doubt you can remove DMSO this way.
If you need pure sample quickly, you may try chromatography first, since it is more general procedure. Finding proper solvents for crystallization requires much more efforts and sometimes good luck.
recrystallization of any solid matter depend on physical properties and purity of materials ,my experience in recrystalization of alloxan by evaporation of water after solubilization
I did not remove DMSO with lyophillization. I first dissolved my solution in water with volume 10 times of the DMSO volume and then I performed the lyophillization.
Anyway, thank you so much for your suggestions. I'll try them and see what happens!
recrystallisation is one of the purification techniques in organic chemistry.U have to select such a solvent where the organic solid is soluble in hot solvent but in soluble in cold solvent.
U have to warm the solvent gradually in a water bath. Then add organic solid sample gradually to make it solubilise in hot condition. Then filter using cotton in hot condition.Cool the resulting liquid .On cooling pure crystals are obtained
Acetonitrile, THF or ethanol might be useful choices. Your flask containing the solids and the necessary volume of solvent should be gradually warmed up until boiling. Carefully place the hot flask on ice-bath and wait the crystals
Check at NMR if the purity of sample is satisfactory
Good luck
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