Preparation, crystal structure and thermal behavior of K(FOX-7)·H₂O

A high-energy organic potassium salt of 1, 1-diamino-2, 2-dinitroethlyene(FOX-7) was synthesized by mixing FOX-7 and KOH in water-methanol system. Crystal structure of K(FOX-7)·H₂O was determined by X-ray diffraction analysis. The crystal belongs to triclinic crystallographic system, space group P1 and cell parameters: a=0.7493(2) nm, b=0.9767(3) nm, c=2.0035(5) nm, α=90.017(4)°, β=97.129(4)°, γ=90.019(4)°, V=1.4548(7) nm³, D_c=1.865 g/cm³, μ=0.724 mm^-1, F(000)=832, Z=8, R₁=0.0523, wR₂=0.1082. The thermal behavior of K(FOX-7)·H₂O was studied, and the apparent activation energy and pre-exponential factor of the second decomposition reaction are 135.9 kJ/mol and 10^12.17 s^-1, respectively. The critical temperature of thermal explosion is 212.02 °C. The specific heat capacity of K(FOX-7)·H₂O was determined with micro-DSC method, and the molar heat capacity is 210.88 J·mol^-1·K^-1 at 298.15 K. Thermodynamic functions of K(FOX-7)·H₂O, relative to the standard temperature 298.15 K, were calculated through thermodynamic relationship, and the adiabatic time-to-explosion also was obtained as a certain value between 15.7-16.8 s.