A study of ethylene carbonate and ethylene monothiocarbonate oriented in a lyotropic nematic phase

Abstract

The proton magnetic resonance spectra of ethylene monothiocarbonate and ethylene sulphite in isotropic media have been recorded and analyzed at 100 MHz to obtain chemical shifts and scalar spin-spin coupling constants. An analysis of the spectrum of the 13C satellites of ethylene carbonate has been completed to obtain values of the proton scalar coupling constants. Both ethylene carbonate and ethylene monothiocarbonate have been used as solutes in a Lyotropic nematic phase consisting of 36% sodium decyl sulphate, 7% decyl alcohol, 7% sodium sulphate and 50% water or D 2O. The spectra are of unusual quality and differ in no significant regard from normal high-resolution proton spectra in isotropic liquids which have line widths of 1 Hz or less. The analysis of these spectra, with the precise scalar couplings from isotropic spectra, allow a determination of dipole-dipole coupling constants to a maximum error of ±0.05 Hz. The spectrum of ethylene carbonate is consistent with an arrangement of four protons at the corners of a rectangle while that for ethylene monothiocarbonate indicates a trapezoidal arrangement of four spins. The symmetry of the four proton spins can be time averaged from small ring-puckering motions of high frequency. Interproton distance ratios of cis-vicinal to geminal protons are larger than expected for a planar 5-membered ring with the totally eclipsed confirmation.