Proton and deuteron nuclear magnetic resonance study of host and guest motions in ethylene oxide-d4 clathrate hydrate

Abstract

The motions of water molecules in ethylene oxide-d4 clathrate hydrate have been studied between 200 and 280 K using continuous wave and pulsed 1H nmr methods. The 1H second moment and rotating frame relaxation time variation with temperature show that reorientation and diffusion of water molecules occur as two distinct processes. From the relaxation time data, activation energies of 8.15 and 12.0 kcal/mol are found for reorientation and diffusion, respectively.From the non-zero guest molecule D quadrupole coupling constant observed between ∼100 and 280 K, it is evident that there is some net orientation of the guest molecules in the hydrate cages at all temperatures. Also, there is a slow motional averaging superimposed on the rapid guest molecule reorientation which can be described approximately by the same parameters as the water molecule reorientation.