Nonlinear dielectric effect study of tetrahydrofuran association in benzene and cyclohexane solutions

The nonlinear dielectric effect (NDE) has been applied to study the molecul ar association in tetrahydrofuran (THF) solutions in benzene and in cyclohe xane. On the basis of the experimental values of the NDE parameter, electri c permittivity, and density, determined as a function of temperature and co ncentration, and applying the general, statistical theory of NDE, the assoc iation constants and dipole moments of the associates were determined. The molecular orbital PM3 method has been applied to calculate the dipole momen ts and energy of molecular clusters. The results of NDE and PM3 studies are fairly consistent and reveal that a weak dipolar association takes place i n the cyclohexane solutions. In the benzene solutions the association, if a ny, is much weaker probably due to competitive interactions between the sol ute and the solvent.