Dielectric relaxation of nitroalkanes in dilute solutions

The relative permittivity at frequencies of 10kHz and 10GHz and the refractive indices have been measured for dilute solutions of (a) nitroethane, (b) 1-nitropropane, (c) 2-nitropropane, and (d) 1-nitrobutane in cyclohexane at 10°, 20°, 30° and 40°C. Materials (b) and (c) together with (e)2-nitro 1-propanol and (f) 2-nitro-l-butanol, have also been studied in different nonpolar solvents. The electric dipole moments, the dielectric relaxation times, and the molar activation energy parameters have been calculated. The results for nitroalcohols show the existence of internal hydrogen bonding between the hydroxyl group and an oxygen atom of the nitro group. The plots of log τ versus log η for materials (b) and (c) are linear for the solvents n-heptane, cyclohexane and decalin. The possibility of interaction of these materials with p-xylene, carbon tetrachloride and p-dioxane are discussed. Activation enthalpy (ΔH_ε) of these materials is observed to be higher in dilute solutions than in pure liquids, and also ΔH_ε for nitrobutane is significantly lower than for the other materials.