Improving the Stability of Trinitramide by Chemical Substitution: N(NF 2 ) 3 has Higher Stability and Excellent Propulsion Performance

The potential for improving the stability of trinitramide (N(NO 2 ) 3 ) by chemical substitution of the NO 2 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‐NO 2 bond dissociation enthalpy (BDE) because of increased stabilization of the N(NO 2 )X radical intermediate resulting from the bond cleavage. This is particularly apparent for N(NO 2 ) 2 NH 2 , 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 NO 2 for the NF 2 group. The resulting molecule, N(NF 2 ) 3 , has a N−N BDE of 138 kJ/mol, which is 17 kJ/mol higher than the N−N BDE of N(NO 2 ) 3 . In contrast to N(NO 2 ) 3 , there are no indications that the stability of N(NF 2 ) 3 is significantly reduced in polar solvents. Condensed phase properties of N(NF 2 ) 3 have been estimated based on surface electrostatic potential calculations, and N(NF 2 ) 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(NF 2 ) 3 in propellant formulations with fuels rich in hydrogen and/or aluminum has been investigated. N(NF 2 ) 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(NF 2 ) 3 and HMX have significantly higher detonation performance than CL‐20.