Vapor Pressures and Energies of Combustion of R-1,2,4-triazoles (R = 3-methyl, 4-methyl, and 4-amino)

This study investigates the volatility of widely utilized triazole derivatives─3-methyl-1 H -1,2,4-triazole, 4-methyl-4 H -1,2,4-triazole, and 4-amino-4 H -1,2,4-triazole─through vapor pressure measurements obtained via the transpiration method in a temperature range of 288–353 K. The standard molar enthalpies of formation, in the crystalline state, at T = 298.15 K, were derived from the standard molar enthalpies of combustion, which were obtained from static bomb combustion calorimetry. From the experimental results, the standard molar enthalpies of formation in the gaseous phase at T = 298.15 K were derived. For comparison purposes, quantum chemical calculations at the G3(MP2)//B3LYP level were performed, using a set of working reactions and the gas-phase enthalpies of formation of both compounds were estimated; the results are in very good agreement with experimental data. Differential scanning calorimetry measurements further supported the investigation by providing complementary thermodynamic parameters, specifically molar heat capacities of triazoles. The vapor pressure data provide key insights into phase transitions, handling risks, detection potential, and the fundamental thermodynamic behavior of these compounds. This work contributes to the improvement on the validation of predictive models relevant to these substances.