An insight into the thermal behaviour of biologically active 8-aryl-4-oxo-4,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazine-3-carbohydrazides

- Thermal behaviour of four biologically active fused 1,2,4-triazinones was studied.
- Compounds are characterized by high thermal stability.
- Three-step thermal degradation of compounds while combustion/pyrolysis is observed.
- First step is related to the violent, exothermic burning of hydrazide fragments.
- Volatile products of pyrolysis were identified.

The combustion and pyrolysis characteristics of four biologically active fused triazinylcarbohydrazides were investigated by using thermogravimetric analysis (in air and nitrogen atmosphere). Together with the analyses performed in nitrogen the FTIR spectra of the evolved gas phase products were recorded. It is indicated that the combustion process can be subdivided into three stages: (i) removing and combustion of the hydrazine fragment; (ii) partial degradation and thermal decomposition of sample; (iii) further cracking process and complete combustion of the remaining parts of compounds. Although the pyrolysis process is also a three-stage one, the last stage is not associated with complete burning of the studied samples. During pyrolysis of all studied compounds, ammonia, carbon dioxide, isocyanic acid, hydrogen cyanide, aniline or its derivatives and carbon monoxide are identified as major products in the FTIR spectra of gaseous products.