Structural Characterization and Thermal Properties of 1-Amino-1-ethylamino-2,2-dinitroethylene

Abstract

1-amino-1-ethylamino-2,2-dinitroethylene (AEFOX-7) was synthesized by the reaction of 1,1-diamino-2,2-dinitroethylene (FOX-7) and ethylamine aqueous solution at 92 °C. The theoretical investigation on AEFOX-7 was carried out by B3LYP/6–311++G** method. The IR frequencies and NMR chemical shifts were performed and compared with the experimental results. The thermal behavior of AEFOX-7 was studied with differential scanning calorimetry and thermal gravity-derivative thermogravimetry methods, and can be divided into a melting process and an exothermic decomposition process. The enthalpy, apparent activation energy and pre-exponential factor of the exothermic decomposition reaction were obtained as 374.88 kJ/mol, 169.7 kJ/mol, and 1019.24 s−1, respectively. The critical temperature of thermal explosion of AEFOX-7 is 145.2 °C. The specific heat capacity of AEFOX-7 was determined with micro-DSC method and theoretical calculation method, and the molar heat capacity is 214.50 J/(mol K) at 298.15 K. The adiabatic time-to-explosion of AEFOX-7 was calculated to be a certain value between 1.38–1.40 s. The thermal stability of AEFOX-7 is much lower than that of FOX-7.

Studies on Thermodynamic Properties of FOX-7 and Its Five Closed-Loop Derivatives

“…It has a density of 1.885 g·cm –3 , a heat of formation of −133.7 kJ·mol –1 , the same insensitivity to TATB (1,3,5-triamino-2,4,6-trinitrobenzene) and a similar energy density as those of RDX (1,3,5-trinitroperhydro-1,3,5-triazine) and HMX (cyclotetramethylene tetranitramine). , Since first being synthesized in 1998, FOX-7 has received much attention and been considered as the main component to be used in insensitive ammunitions and solid propellants. Many research studies have been carried out on the synthesis, mechanism, molecule structure, thermal behavior, detonation performance, and application of FOX-7. − FOX-7 is a representative “push–pull” nitro-enamine compound, which possesses a highly polarized carbon–carbon double bond with positive and negative charges being stabilized by the amino group and nitro group, respectively. ,, The positive end of the carbon–carbon double bond can be attacked by nucleophilic reagents to synthesize new singly substituted derivatives or disubstituted closed-loop derivatives. ,− Five disubstituted closed-loop derivatives of FOX-7 (Scheme ) were synthesized by our group, and their structures and some properties were reported in succession. − …”