Some physical properties associated with the urethane group—I.: N-ethyl urethane

Abstract

The enthalpy of hydrogen bond formation in N-ethyl urethane is estimated from i.r. and NMR data as about -2kcal.mole t̄1. From a comparison of the dielectric relaxation properties in the ultra high frequency region with the viscous flow and spectral properties of the N-ethyl urethane, it is concluded that in non-polar solvents dielectric orientation polarization involves the fracture and reformation of long hydrogen-bonded chains of N-ethyl urethane molecules. The activation energies for dielectric relaxation and for viscous flow in undiluted N-ethyl urethane are both 6·5 kcal.mole t̄1. In ethereal or ester solvents N-ethyl urethane hydrogen-bonds to the solvent and the activation energies for flow and dielectric reorientation processes are reduced; it is suggested that urethane solvent interactions are most important in determining flow or dielectric orientation processes. Dipole moments and NMR chemical shifts for N-ethyl urethanes are also reported.