A solvent having switchable hydrophilicity

A new kind of switchable solvent, a switchable-hydrophilicity solvent, is hydrophobic and has very low miscibility with water when in air but is hydrophilic and has complete miscibility with water when under an atmosphere of CO2. We report here the first example of such a solvent, N,N,N′-tributylpentanamidine. Solvents such as these could be used for the extraction of low-polarity organic products, such as vegetable oils, followed by the removal of the solvent from the product by carbonated water. Carbonated water is able to extract the solvent from the product because the CO2 converts the solvent to its hydrophilic form. The solvent can then be separated from the carbonated water upon removal of the CO2, because this removal triggers the conversion of the solvent back to its hydrophobic, water-immiscible form. Importantly, distillation is not required for removal of the solvent from the product.