Improving the Stability of Trinitramide by Chemical Substitution: N(NF2)3 has Higher Stability and Excellent Propulsion Performance

Abstract

AbstractThe potential for improving the stability of trinitramide (N(NO2)3) by chemical substitution of the NO2 group has been investigated using Kohn‐Sham density functional theory [M06‐2X/6‐31+G(d,p)] and ab initio quantum chemistry [CBS‐QB3]. Monosubstituted analogs are generally found to have a decreased N‐NO2 bond dissociation enthalpy (BDE) because of increased stabilization of the N(NO2)X radical intermediate resulting from the bond cleavage. This is particularly apparent for N(NO2)2NH2, which has a BDE of only 54 kJ/mol. Instead it is shown that the stability of TNA can be significantly improved by substituting all three NO2 for the NF2 group. The resulting molecule, N(NF2)3, has a N−N BDE of 138 kJ/mol, which is 17 kJ/mol higher than the N−N BDE of N(NO2)3. In contrast to N(NO2)3, there are no indications that the stability of N(NF2)3 is significantly reduced in polar solvents. Condensed phase properties of N(NF2)3 have been estimated based on surface electrostatic potential calculations, and N(NF2)3 is estimated to be a liquid in the approximate temperature range of 170–290 K because of its nonpolar character. The performance of N(NF2)3 in propellant formulations with fuels rich in hydrogen and/or aluminum has been investigated. N(NF2)3 propellants are shown to outperform propellants based on standard oxidizers by up to 20 % in specific impulse and up to 100 % in density impulse. Compositions of N(NF2)3 and HMX have significantly higher detonation performance than CL‐20.