Abstract
We have shown, earlier, that profens, i.e., 2-arylpropionic acids can undergo oscillatory in vitro chiral conversion, exhibiting oscillatory changes in the chromatographic retention parameter (R F) and the specific rotation ([α]D) for periods of up to two weeks after preparation of the solutions in aqueous ethanol. Here, we examine the oscillatory chiral conversion of S-(+)-ibuprofen and S,R-(±)-ketoprofen dissolved in 70% aqueous ethanol and stored in tightly closed colorless glass vials for one year. During that time, each initially homogenous, transparent profen solution separates into two immiscible layers, one clear and the other turbid. Employing chiral thin layer chromatography, high performance liquid chromatography with diode-array detection, gas chromatography, and Raman spectroscopy, we find that both samples undergo chiral conversion to yield a strong predominance of the R-(−) antimer. Additionally, microscopy reveals characteristic spatial patterns in both layers of the demixed ibuprofen and ketoprofen solutions. We use a model proposed earlier for the homogeneous oscillatory interconversion of the S and R profens involving two linked templators to simulate microscopic spatial patterns analogous to those observed in the solutions investigated here.