I have been trying to purify a small molecule containing N-hydroxy and ketone group. The synthesis involved use of weak inorganic base e.g., sodium carbonate. Typically the purification used extraction or recrystallization using a polar organic solvent like ethanol or acetone to extract the polar molecule.

However the phenomenon is like this:

1. Once ethanol was added to the mixture in excess, white precipitate forms with water as "oil" stuck to the bottom of a flask. In this case, I could only purify some of the salt but not the target compound.

2. I also tried rotary evaporation, but the final form is a very sticky and gummy.

3. I then tried to dry the water at 120 C, leaving the salt and compound in the solid and tried to use polar organic solvent to extract it. Nothing or very little was dissolved, leaving colored solid at the bottom.

4. Recrystallization was also attempted, but since water is much less volatile and favors solute dissolution, the result is basically a precipitation of salt.

5. I have tried to add acid to change the pH condition, but the result is similar.

So the question is, is there any other good way to purify this hydrophilic, highly polar compound from salt?

More Kuang-Hsu Wu's questions See All
Similar questions and discussions