Investigation by Nuclear Magnetic Resonance of the Effects of Pressure on the Thermal Transition and Rotator Phase of 2,2-Dinitropropane

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Abstract
The thermal transition for 2,2‐dinitropropane, which normally occurs at —5°C, is observed at various pressures up to 1000 kg/cm2 in terms of the proton magnetic resonance line width. The spin‐lattice relaxation time (T1) is observed for temperatures from —11°C to 65°C, at atmospheric pressure and under 1000 kg/cm2. The compressibility and the specific volume are measured, and x‐ray powder patterns are compared, for temperatures above and below the transition. The latent heat of transformation and specific heat, above and below the transition, are calculated. Self‐diffusion sets in at the transition, for all pressures studied. Under pressure, molecular rotation in the higher temperature phase is restricted and T1 is insensitive to temperature. The correlation time for molecular rotation at atmospheric pressure and 50°C is 7×10—12 sec, in fair agreement with dielectric data. The temperature dependence of T1 suggests that the fraction of molecules subject to rotation in the upper phase increases with the temperature.

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