Thermochemical studies of 3-methylpyrazole and 1,3,5-trimethylpyrazole

The standard (p∘=0.1MPa) molar enthalpies of formation, at T=298.15K, in the condensed phases of two alkylpyrazoles, viz.   3-methylpyrazole and 1,3,5-trimethylpyrazole, were determined by static bomb calorimetry. Calvet microcalorimetry was used to measure the standard molar enthalpy of vaporisation of 1-methylpyrazole and the standard molar enthalpy of sublimation of 1,3,5-trimethylpyrazole. From these two sets of results, the standard molar enthalpies of formation of both alkylpyrazoles in gaseous phase, at T=298.15K, were derived. -ΔcUm∘(cr or l)kJ·mol-1Δcr, or lgHm∘kJ·mol-1ΔfHm∘(g)kJ·mol-13-Methylpyrazole2504.5±1.665.9±2.0140.1±2.61,3,5-Trimethylpyrazole3806.4±1.861.7±1.681.6±2.6Full-size tableTable optionsView in workspaceDownload as CSV The final results were analysed and discussed in terms of molecular structure.