ИСТИНА

Physico-chemical characterization of low-melting oxygen-rich energetic N trinitromethyl-3,4-dinitropyrazole (1), N-trinitromethyl-3,5-dinitropyrazole (2), N-flurodinitromethyl-3,5-dinitropyrazole (3), and N-[(difluroamino)dinitromethyl]-3,5-dinitropyrazole (4) has been conducted, including studies on the thermal decomposition, burning behavior, and flame structure. Combustion studies of the nitropyrazoles have shown that all the compounds have similar pressure exponents in the burning rate law rb=Apn, slightly less than unity (0.87-0.89). The burning rates at 10 MPa vary from 26.8 mm s 1 (for 1) to 77.5 mm s 1 (for 4). The surface temperature of nitropyrazoles has been shown by thermocouple-aided measurements to be controlled by evaporation and be close to the surface temperature of nitroglycerine NG. It has been found that the stability of N-substituted trinitromethyl azoles is relatively higher than stability of similar C-substituted azoles. Substitution of the nitro group by the fluorine or difluoromine group in the trinitromethyl substituent results in a change in the C-NO2 bond length and the corresponding change in the thermal stability. However, there is no linear correlation between the rate constants and the C-NO2 bond length, which indicates the presence of other factors affecting the stability of trinitro- and substituted dinitromethyl derivatives. An analysis of thermocouple data shows that the burning rate of nitropyrazoles 1, 2, and 4 depends on the rate of heat release in the condensed phase, which, in turn, is determined by decomposition kinetics at the surface temperature. The increase in the stability of the fluoro derivative 3 leads to a drop in the depth of decomposition in the melt even despite an increase in the surface temperature, and converts the leading reaction of its combustion into the gas phase.