Calorimetric, dielectric, and infrared investigations of solid t-butyl chloride

Results of calorimetric, dielectric and infrared measurements for solid t-butyl chloride ((CH3)3CCl) are presented. Calorimetric data confirm earlier results that there are two phase transitions in the solid state of this substance. Transition temperatures, enthalpy, and entropy values are in good agreement with literature data. The transitions found at 181.1 and 219.4 K are interpreted as first-order transitions, whereas that at 248.4 K (the melting point) is described to a 2I transition according to the classification of McCullough. Permittivity measurements in the microwave region were performed in the range of temperatures from the melting point to approximately 200 K. The data reveal the presence of dielectric dispersion in this frequency range, thus corroborating the results of other authors. Results for the plastic crystalline phase satisfy the Cole–Cole relation with a distribution parameter of dielectric relaxation times, α, equal to zero. Dielectric relaxation times were computed for several temperatures and the activation energy was estimated on the basis of three activation models. The infrared absorption spectrum in the range 400 to 1500 cm−1 shows that in phase I the spectrum is almost identical with that of the liquid phase and that in phase II each of the four bands is distinctly split into two components. Changes in the spectrum are interpreted as due to Davydov splitting associated with various depths of potential wells.