Isoconversional kinetic analysis of decomposition of nitropyrazoles

The thermal decomposition kinetics of pyrazole, N-nitropyrazole, 3-nitropyrazole and 4-nitropyrazole using TG–DTA technique under nitrogen atmosphere has been investigated. Friedman differential and Flynn–Wall–Ozawa integral methods were used to determine the kinetic parameters. The calculated activation energies are believed to be fairly well and qualitatively good in providing mechanistic clues. Pyrazole, 3-nitropyrazole and 4-nitropyrazole were decomposed by the multi step decomposition kinetics evident from the non-linear relationship of activation energy and the conversion rate. However, N-nitropyrazole was decomposed by single step decomposition or the unification of multistep decomposition kinetics evident from the linear relationship of activation energy and the extent of conversion. The present study may help to understand how the position and the number of nitro groups affect the decomposition kinetics of azoles and their possible use for the generation of vinylcarbenes.

► Azoles undergo peculiar decomposition mechanism.
► Pyrazole and C-nitropyrazoles decomposed by multi step kinetics.
► N-nitropyrazole decomposed by single or unification of multistep kinetics.