Dielectric Relaxation of Binary Mixtures of Tetrahydrofuran and N-Methylformamide in Benzene Solution Using Microwave Absorption Studies

摘要

Using standard standing wave microwave X-band technique and following Gopala Krishna's single frequency (9.90 GHz) concentration variational method, the dielectric relaxation times τ and the dipole moments μ of dilute solutions of Tetrahydrofuran (THF), N-methylformamide (NMF), and THF+NMF binary mixtures in benzene solutions have been calculated at different temperatures (25 °C, 30°C, 35 °C, and 40°C). The energy parameters (ΔH_ε, ΔF_ε, ΔS_ε)for the dielectric relaxation process for the THF+NMF binary mixture containing 30 mol% THF have been calculated at 25 °C, 30 °C, 35 °C, and 40 °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 process can be treated as a rate process. From relaxation time behaviour of THF and NMF binary mixture in benzene solution, solute-solute types of the molecular association has been proposed.