Hello Po-Hsi Lin ,

I guess strongly acidic ion exchangers could help you to remove the sodium cations to get a solution from which the pure phenylbutyric acid can be crystallised. I wish you much success in your research.

Dear Po-Hsi Lin thank you for posting this interesting technical question on RG. The ion exchange as suggested by Florian Morsbach is perhaps the most elegant method for preparing the free phenylbutyric acid from sodium phenylbutyrate. If you are not familiar with the use of ion exchangers, you can also add HCl or sulfuric acid until the solution is acidic, and then extract the free acid with diethyl ether (3 times). Dry the extract with anhydrous Na2SO4 or MgSO4 over night, filter, and evaporate the filtrate using a rotary evaporator. The residue can be purified by distillation under vacuum as described in the attached literature reference. When the sample is pure, it will crystallize at room temperature (melting point 46–48 °C).

Good luck and best wishes, Frank Edelmann

Thank everyone. I will try it