Molecular charisma in supercritical fluids

The unique properties of supercritical fluids (SCF) solutions near the critical region are often a manifestation of local properties which are significantly different than bulk properties. A variety of spectroscopic measurements, as well as thermodynamic and theoretical treatments, support the existence of local density and local composition augmentations in the vicinity of large solute molecules in SCF solutions. Opportunities to exploit this concept of molecular charisma exist for a variety of engineering application including separations using cosolvent/SCF systems and chemical reactions in SCF solvents. The component of cosolvent effect on solubilities in SCF systems resulting from molecular charisma is discussed and related to specific solute/cosolvent interactions and cosolvent concentration. As a consequence of two effects of molecular charisma, the potential to adjust reaction rates and reaction selectivities in SCF solvents is also enhanced. Reaction rates may be altered through the concentration of reactants at the reaction site. Additionally, modification of local solvent strength in SCF solutions, a property of the local reactant environment, can alter reaction rates and selectivities.