p,T Dependence of Self-diffusion in Fluoroethanols.

Abstract

The self-diffusion of ethanols substituted by fluorine at the methyl carbon has been studied by FTNMR using pulsed gradient spin-echo techniques for the first time. The results showed that the effects of adding fluorine appear to be steric in nature, with little effect of changing the hydroxyl hydrogen bond strength. 2,2-difluoroethanol has a more pronounced temperature dependence than 2-fluoroethanol or 2,2,2-trifluoroethanol.In addition, analysis of the experimental data to a VTF type equation reveals that 2,2-difluoroethanol has a much higher ideal glass transition temperature, To, than either 2-fluoroethanol or TFE. These data indicate that steric conformations in difluoroethanol produce more stable hydrogen bonded structures than in the other two liquids.There is little evidence from these selfdiffusion data of anv effect of intra-molecular hvdroeen bonding.[ Self-diffusion, fluoroethanols]