THERMODYNAMIC PROPERTIES AND PHASE-TRANSITIONS OF 1-METHYLCYCLOHEXANOL AND 1-CHLORO-1-METHYLCYCLOHEXANE

Comprehensive investigations of thermodynamic properties of 1-methylcy clohexanol (I) and 1-chloro-1-methylcyclohexane (II) were carried out. The heat capacities and enthalpies of transitions of I and II in the condensed state between 5 and 320 K were measured by vacuum adiabatic calorimetry. It was found that II exists in the plastic crystal state over a narrow temperature interval from 214.37 to 234.52 K. The enthal pies of sublimation of I and vaporization of II and their saturated va por pressures were obtained. Infrared (LR) and Raman spectra of both c ompounds were recorded and vibrational analyses were made. Thermodynam ic functions of I and II in the ideal gas state were calculated by the statistical thermodynamics methods. It was shown by the low-temperatu re LR spectroscopy that only one 'chair'-conformer of II with equatori al methyl group exists in rigid crystal phase at T<214.37 K. The natur e of molecular rotation in the plastic crystal state of II is discusse d. (C) 1998 Elsevier Science B.V.