In order to obtain a better understanding of thermal substituent effects in 1,2,4-triazole-3-one (TO), the thermal behavior
of 1,2,4-triazole, TO, as well as urazole and the decomposition mechanism of TO were investigated. Thermal substituent effects
were considered using thermogravimetry/differential thermal analysis, sealed cell differential scanning calorimetry, and molecular
orbital calculations. The onset temperature of 1,2,4-triazole was higher than that of TO and urazole. Analyses of evolved
decomposition gases were carried out using thermogravimetry–infrared spectroscopy and thermogravimetry–mass spectrometry.
The gases evolved from TO were determined as HNCO, HCN, N2, NH3, CO2, and N2O.