Motional narrowing of the fluorine N.M.R. in the halothane-trithymotide clathrate

The motional narrowing of 19F N.M.R. resonance of the halothane tri-o-thymotide clathrate was studied as a function of temperature. It was shown that the CF3 group exhibits free rotation about its C3 axis at temperatures as low as 108 K. Other motional narrowings were observed as the temperature was raised and finally at a temperature of about 25 K below the melting point of the clathrate diffusion of the halothane molecules through the lattice reduced the second moment to practically zero.