Thermodynamics of polymerisation of heterocyclic compounds. Part IV. The heat capacity, entropy, enthalpy and free energy of paraldehyde

Abstract

AbstractAn adiabatic calorimeter has been used to measure the heat capacity of paraldehyde from 80 to 310°K. An estimate has been made of heat capacity values below 80°K. Entropy, enthalpy and free energy values have been derived and are listed at 10° intervals. Published vapour pressure data have been used to calculate the entropy of paraldehyde gas at one atmosphere pressure and 298.16°K. The value obtained is 89.50 ± 1.20 cal deg−1 mole−1. The thermal behaviour of paraldehyde in the solid state is complex; transitions occur between four different crystalline forms of paraldehyde at 142.7, 147.5, and 230.3°K, respectively. The melting transition occurs at 285.7°K. The entropies of isotactic and syndiotactic polyacetaldehyde have been estimated as 13.8 ± 0.2 and 17.1 ± 0.2 cal deg−1 mole−1 respectively.