Analysis of the Internal Rotation of the · CF2CONH2 Radical as Observed by ESR in Irradiated Trifluoroacetamide Single Crystals

The temperature‐dependent ESR spectrum of the $·{\mathrm{CF}}_2{\mathrm{CONH}}_2\mathrm{radical}$ (found in x‐irradiated single crystals of trifluoroacetamide) has been measured at both 9 and 35 GHz over the temperature range from 77 to 290°K. A model is proposed which explains the observed temperature dependence in terms of a torsional oscillatory motion about the $\mathrm{C}–\mathrm{C}$ bond with a barrier height, V₀=3100 cal. Nonadiabatic spin exchange is used to account for the doublet splitting of the central line at 77°K changing to a single sharp line at all angles at 290°K. The exchange rate is described by the empirical equation $r^{\text{−1}}{\text{=3.6 × 10}}^8\hspace{0.17em}\exp \text{(−410\hspace{0.17em}}\mathrm{cal}\mathrm{/RT)}$ .