Carbon dioxide-expanded liquids as environmentally benign process solvents

Gas-expanded liquids are particularly exciting alternative solvents because they have many of the benefits of supercritical fluids, but at much lower pressures. The tunability of these solvents makes them ideal candidates for fine separations and reactions that are dependent on solvent power. In this work, gas-expanded are examined as a reactions and separations medium. The first reported use of gas antisolvent crystallization as a chiral separation method is reported here. This process takes advantage of the different physical properties of diastereomers to cause crystallization of one of the diastereomer from methanol by the addition of CO₂ as an antisolvent.; The crystallization work leads into an examination of interactions between carbon dioxide and short chain alcohols in CO₂-expanded liquids and supercritical CO₂ with alcohol cosolvents. These mixtures are shown to be innately acidic due to the reversible, in situ formation of alkylcarbonic acids. These acidic are compared to carbonic acid, the well-known analogue formed from water and CO₂.; The second half of this work concentrates on the concept of fluorous biphasic chemistry and related phase behavior. Fluorocarbons are shown to become miscible with organic solvents when modest CO₂ pressure is applied. The benefits and applications of this phenomenon are also considered. Additionally, several new concepts in fluorous phase catalysis are presented.