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-methylcyclopentano l (I) and 1-chloro-1-methylcyclopentane (II) in the condensed state we re measured by vacuum adiabatic calorimetry in interval from 5 to 315 K. It was found that these compounds formed glasses by their cooling f rom 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 308.5 3 K. The correlation between the entropies of transitions of I testifi es 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 tran sition crII --> crI to that of fusion for II exceeds 8. This fact conf irms that II forms the plastic crystal state even in a very narrow int erval from 178.82 to 189.05 K. The thermodynamic characteristics of gl assy 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 com pounds on the base of possible structural changes of molecules and sub stances at T-g.