Measurement and Prediction of Octanol-Water Partition Coefficients for Selected Room Temperature Ionic Liquids

Octanol-water partition coefficients provide important information about the hydrophobicity or hydrophilicity of a substance. In this case ionic liquids are the focus due to their advantages for green engineering. Since they are non-volatile, thermally stable organic compounds they have many potential applications in industrial processes. They will replace solvents or catalysts in many synthetic reactions due to their high polarity, varying degrees of solubility in organic compounds, significant electrical conductivity, thermal stability, and negligible vapor pressure. A fast and inexpensive method utilizing the HPLC can estimate the logarithm of the octanol-water partition coefficient (log Pow). This method uses a 15-cm octadecyl-poly(vinyl alcohol) (ODP) column and a methanol-water gradient to provide a correlation between retention time and log(Pow). This testing focused on low log(Pow) values characteristic of ionic liquids (specifically ionic liquids of the imidazolium family). This method has a run time of 18 minutes versus the traditional method which takes several days. A discussion of new developments will also be covered.