Molecular associations in binary mixtures of pyridine and chlorobenzene in benzene solution using microwave absorption data

The dielectric relaxation time (τ) of binary mixtures of different molar concentrations of pyridine (C5H5N) and chlorobenzene (C6H5Cl) in benzene solution at different temperatures (25, 30, 35 and 40 °C) has been calculated by using standard microwave techniques and Gopala Krishna's single frequency (9.875 GHz) concentration variation method. The energy parameters (ΔHε, ΔFε, and ΔSε) for the dielectric relaxation process of the binary mixture containing 0.5 mol fraction of pyridine have been calculated at the respective temperatures. Comparisons have been made with the corresponding energy parameters for the viscous flow (ΔHη, ΔFη, and ΔSη). From the observations it is found that the dielectric relaxation process can be treated as the rate process. Based upon above studies, solute-solvent type of molecular associations arising from the interaction of chlorobenzene and benzene and pyridine and benzene molecules has been proposed. No solute-solute type of molecular association has been observed.