Synthesis, crystal structure and thermal behaviors of 2,3-dihydro-4-nitro-3-(dinitromethylene)-1H-pyrazol-5-amine potassium salt [K(NNMPA)

Abstract

A novel high-energy organic potassium salt, 3-(dinitromethylene)-4-nitro-2,3-dihydro-1H-pyrazol-5-amine potassium salt [K(NNMPA)], was first synthesized by an unexpected reaction of 1-amino-1-hydrazino-2,2-dinitroethylene (AHDNE) and KOH in methanol aqueous solution. K(NNMPA) was characterized by elemental analysis, IR spectra, 13C NMR and single-crystal X-ray diffraction. K(NNMPA) crystallized in monoclinic system, space group P21/c with crystal parameters of a=9.358(3)Å, b=13.079(4)Å, c=7.568(2)Å, β=107.344(5)°, V=884.2(5)Å3, Z=4, μ=0.638mm−1, F(000)=544 and Dcalc=2.03gcm−3. Thermal decomposition of K(NNMPA) was studied with DSC and TG-DTG methods and presents two exothermic decomposition processes. The kinetic equation of the first process obtained is dαdT=1018.42β4(1-α)[-ln(1-α)]3/4exp(-1.665×105/RT). The self-accelerating decomposition temperature (TSADT) and critical temperature of thermal explosion (Tb) of K(NNMPA) are 137.4 and 146.3°C, respectively. K(NNMPA) exhibits lower thermal stability than K(AHDNE).