Dynamics in benzene-hexafluorobenzene solution forming specific interaction

Abstract

The concentration dependence of the dynamic properties for the benzene (C₆H₅) hexafluorobenzene (C₆H₅) mixture has been investigated to test the extended conformal solution (ECS) theory against the negative excess enthalpy (<em>H</em>^E) system; the dynamic properties studied are second order orientational correlation time (t_2R) of a benzene-d₆, (C₆D₆) molecule, translational self-diffusion coefficient (D ) of the respective components, and viscosity (h). The respective dynamic properties have been fitted to the quadratic equations on the mole fraction of C₆H₅, 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 thennodynamically attractive force (negative IF ) slows down the reorientational motion of a C₆H₅ molecule in the C₆H_{5 -}C₆F₅mixture. The validity of the Stokes-Einstein (SE) and Stokes-Einstein-Debye (SED) laws have also been checked for t_2R and <em>D</em>. Both laws break down in the low viscosity ranges. The thennodynamically attractive force also enlarges the microscopic specific reorientational and translational parameters.