Ionic liquids have been touted as the next great class of environmentally-friendly solvents due to their lack of vapor-pressure and molecularly “tunable” properties. However, reports of their synthesis often include the very solvents that they will purportedly replace. Moreover, ionic liquids are often too costly as industrial-scale replacements solvents. As kinetic and thermodynamic data of their synthesis is nearly non-existent in the literature, little to no emphasis has been placed on reactor engineering and process intensification to reduce the cost of the ILs. For ionic liquids to be truly sustainable and to be used ubiquitously, they themselves must be made in a correspondingly benign manner in potentially large quantities and for low cost. This presentation will elaborate on the dramatic effect of the solvent on the kinetics of common quaternization reactions. The kinetic constants are both sensitive to the solvent and concentration of the reactants. Solvatochromic probes and linear solvation energy relationships (LSER) have been used to connect measures of “polarity” with kinetic rate for these reactions. Solvent selection in light of principles of green chemistry and engineering is discussed. Compressed CO₂ has been shown to be an attractive tunable reaction/separation medium. Phase behavior with CO₂ has a large implication on both the reaction and separations scheme and can be used to optimize the entire process of this environmentally-benign medium.