Dielectric relaxation studies of mixtures of N-methylacetamide and ethanol in benzene solutions using microwave absorption technique

Using standard standing wave microwave X-band techniques, and by following Gopala Krishna's single frequency (9.90 GHz) concentration variational method, the dielectric relaxation times (2) and dipole moments (mu) of binary mixtures of different molar concentrations of ethanol (EtOH) in binary mixtures of N-methylacetamide (NMA) and ethanol in benzene solutions at 25, 30, 35 and 40 degrees C have been calculated. The activation parameters (Delta H epsilon, Delta F epsilon, Delta S epsilon) for the dielectric relaxation process of binary mixtures containing 30 mol% of EtOH have been calculated at 25, 30, 35 and 40 degrees C and compared with the corresponding viscosity parameters. A good agreement between the free energy of activation from these two sets of values shows that the dielectric relaxation process, like the viscous flow, can be treated as a rate process. From relaxation time behaviour of NMA and EtOH binary mixtures in benzene solution, solute-solute and solute-solvent types of the molecular association have been predicted.