Dielectric properties and structure of N-methylpropionamide + methanol mixtures

Abstract

The dielectric properties of mixtures of methanol with N-methylpropionamide (NMP) at 20 °C have been investigated over the range of frequency 1 MHz to 4 GHz. The dielectric relaxation is described by a simple Debye dispersion equation, in contrast with the behaviour for many non-aqueous mixtures. An exponential dependence of the relaxation frequency on mole fraction composition reveals two distinct regions of dielectric response, attributed to methanol-dominated and NMP-dominated liquid structures. Results are discussed in terms of the polarisation of a homogeneous liquid of uniformly hydrogen-bonded structure, which varies in character with solvent composition.