Physical Chemistry of Binary Plastic Crystals. I. The System of Carbon Tetrachloride and t-Butyl Iodide

The binary system, carbon tetrachloride- t-butyl iodide, was studied by the proton magnetic resonance, the dielectric measurements and the X-ray diffraction. The complete phase diagram, constructed by the differential thermal analysis, shows a solid solution region where carbon tetrachloride is more than 50 mole%. Detailed studies of the solid solution containing 6.6 mole% of t-butyl iodide reveals that the solution can be described by the theory of regular solutions; its molecular polarization above the transition temperature obeys the Debye formula giving the dipole moment of t-butyl iodide a value of 1.6 debye units. The high-resolution nuclear magnetic resonance experiments with the same phase shows that carbon tetrachloride molecules diffuse in the solid solution with an energy of activation of 6.8 kcal./mole. The transition temperature varies with the composition, and below it the rotational motion of the solute molecules is more hindered. Pure t-butyl iodide shows motional narrowing around –150°C in the NMR line shape, above which temperature a reorienting molecular model can account for the magnitude of second moment of the nuclear magnetic resonance absorption.