The effect of pressure on the conformational isomerization of cyclohexane innhyphen;pentanehyphen;d12solvent has been investigated by using the highhyphen;resolution, highhyphen;pressure nuclear magnetic resonance (NMR) technique. The isomerization rate of cyclohexane increases with increasing pressure at 218 K. The experimental data are interpreted in terms of stochastic models for isomerization reactions, and the results show that cyclohexane isomerization innhyphen;pentanehyphen;d12exhibits behavior typical for lowhyphen;friction, energy controlled regime. The effect of temperature and pressure on the conformational isomerization of 1,1hyphen;difluorocyclohexane in solution has been investigated with the use of19F Fourier transform (FT) NMR spectroscopy. The solvents used in this study arenhyphen;pentane, acetonehyphen;d6, and methylcyclohexane. Similarly, as in the case of cyclohexane, the ring inversion in 1,1hyphen;difluorocyclohexane is accelerated when pressure is increased, and this pressure dependence is nonlinear. The interpretation of the experimental data for 1,1hyphen;difluorocyclohexane depends critically on the estimate of Dgr;VDagger;TSTwhich value is not known at the present time. Therefore, it is impossible to determine whether isomerization of 1,1hyphen;difluorocyclohexane exhibits the Kramers turnover.
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