Dynamics in benzene-hexafluorobenzene solution forming specific interaction

The concentration dependence of the dynamic properties for the benzene (C-6-H-6) - hexafluorobenzene (C6F6) mixture has been investigated to test the extended conformal solution (ECS) theory against the negative excess enthalpy (H-E) system; the dynamic properties studied are second order orientational correlation time (tau(2R)) of a benzene-d(6) (C6D6) molecule, translational self-diffusion coefficient (D) of the respective components, and viscosity (eta). The respective dynamic properties have been fitted to the quadratic equations on the mole fraction of C6H6, and the quadratic (regular) terms are obtained. The strong interaction between unlike components has been recognized through the sizes and signs of the regular terms of the respective dynamic properties. In particular, the thermodynamically attractive force (negative H-E) slows down the reorientational motion of a C6H6 molecule in the C6H6-C6F6 mixture. The validity of the Stokes-Einstein (SE) and Stokes-Einstein-Debye (SED) laws have also been checked for tau(2R) and D. Both laws break down in the low viscosity ranges. The thermodynamically attractive force also enlarges the microscopic specific reorientational and translational parameters.