Pressure Tuning of Chemical Reaction Equilibria in Supercritical Fluids

Article abstract of DOI:10.1021/j100347a076

Supercritical fluid solvent effects were studied for the tautomeric equilibria of 2-hydroxypyridine and 2-pyridone at infinite dilution, both experimentally and theoretically.The fluids were propane at 393 K and 1,1-difluoroethane at 403 K, and pressures ranged from 21 to 206 bar.The equilibrium constant, K_c, which was measured by in situ UV spectroscopy, increased 4-fold a pressure increase of 400 bar in 1,1-difluoroethane, with a partial molar volume change on reaction reaching -1400 cm³/mol.A thermodynamic model was developed to increase the range of pressures studied and to explore temperature effects.The tuning of chemical reaction equilibria is a powerful technique for charaterizing a key advantage of supercritical fluid solvents, wich is their enormous adjustabilyty.