Impact of fluorine on the phase behavior of bisphenol-type compounds in Supercritical-CO2, 1,1-difluoroethane, and 1,1,1,2-tetrafluoroethane

Phase behavior data are reported for 2,2-bis(4-hydroxyphenyl) propane (BPA) and 2,2-bis(4-hydroxyphenyl) hexafluoropropane (BPAF) in CO2, difluoroethane (F152a), and tetrafluoroethane (F134a). BPA dissolves in F152a but not in CO, or F134a. BPAF is most soluble in F152a, moderately soluble in F134a, and least soluble in CO2. Aromatic rotation in BPAF is hindered by the CF3 groups, which is expected to reduce configurationally dependent BPAF-BPAF hydrogen bonding. Although both freons have similar polarizabilities and dipole moments, F152a is a superior solvent with a larger effective dipole moment due to its smaller molar volume. Also, the electrostatic potential field of F152a projects slightly beyond the molecular dimension of the fluorine and hydrogen atoms more so than with F134a, suggesting that F152a exhibits stronger electrostatic interactions over greater separation distances than F134a. Hence, fluorine has a significant effect on the phase behavior whether fluorine is added to the solute or solvent.