The dielectric properties of ethyl and methyl carbamates in aqueous solution

Abstract

Dielectric dispersion of aqueous solutions of ethyl carbamate (urethane, EC), methyl carbamate (urethylan, MC) and their eutectic mixture (‘liquithane’, EMC) has been measured. The partial static polarization of the polar fractions of all these solutions is the same and is attributed jointly to water and to the polar radicals of the solutes. The dielectric dispersion measurements show a single asymmetric dispersion band with a principal relaxation frequency which is displaced in approximate proportion to solution viscosity. The high-frequency ‘tail’ is consistent with a Davidson–Cole distribution parameter β of ca. 0.8, although other interpretations are possible. An alternative treatment of the data obtained at 70 GHz sees the modification of the relaxation frequency of water as equivalent to the binding of 2–5 mol of water per mol of carbamate.