Heat capacities and enthalpies of transitions of 1-methylcyclopentanol and 1-chloro-1-methylcyclopentane in the condensed state

Heat capacities and enthalpies of transitions for 1-methylcyclopentanol (I) and 1-chloro-1-methylcyclopentane (II) in the condensed state were measured by vacuum adiabatic calorimetry in interval from 5 to 315 K. It was found that these compounds formed glasses by their cooling from 310 K at a rate (0.03-0.05)K . s(-1). The crystal I undergoes two solid-to-solid transitions at 281.72 K and 301.47 K and melts at 308.53 K. The correlation between the entropies of transitions of I testifies that it does not form the plastic crystal phase. Two solid-to-solid transitions at 164.20 K and 178.82 K occurred in the crystal II. The fusion temperature of II is 189.05 K. The ratio of the entropy of transition crII --> crI to that of fusion for II exceeds 8. This fact confirms that II forms the plastic crystal state even in a very narrow interval from 178.82 to 189.05 K. The thermodynamic characteristics of glassy I and II were obtained and the thermodynamic analysis of the heat capacity jump at T-g and the residual entropies was made for both compounds on the base of possible structural changes of molecules and substances at T-g.