Extending the range of switchable-hydrophilicity solvents.

A switchable-hydrophilicity solvent (SHS) is a solvent that in one state forms a biphasic mixture with water but can be reversibly switched to another state that is miscible with water. All of the amine SHSs that we have reported previously lie within a particular basicity and hydrophilicity range (9.5 < pKaH < 11 and 1.0 < log Kow < 2.5, respectively). We report an extension of this range by altering the pressure of CO2 as well as the water : SHS volume ratio used in the process. Increasing the pressure of CO2 and/or the water : amine volume ratio allows some amines with pKaH < 9.5 or log Kow > 2.5 to function as SHSs.