Journal of Chemical Thermodynamics, Vol.26, No.11, 1219-1230, 1994
Heat-Capacities Between the Temperatures 10-K and 445-K for 2,4-Dimethylpyrrole and Barriers to Methyl-Group Rotation in the Solid-State for 2,4-Dimethylpyrrole and 2,5-Dimethylpyrrole
Heat capacities and enthalpy increments between the temperatures T = 10 K and 445 K were determined for 2,4-dimethylpyrrole by adiabatic calorimetry. (Chemical Abstract registry number [625-82-1].) The triple-point temperature and enthalpy of fusion are reported, and enthalpies and entropies relative to those of the crystals at T --> 0 were derived. No crystal-to-crystal phase transitions or anomalies were observed. Heat capacities for the supercooled liquid were determined between the glass transition and triple-point temperatures. Barriers to methyl-group rotation in the solid state for 2,4-dimethylpyrrole and 2,5-dimethylpyrrole were estimated by comparison of the heat capacities of the crystals for 2,4-dimethylpyrrole with literature values for 2,5-dimethylpyrrole.