Design of new aliphatic azido nitro compounds as plasticizer: an initial exploration on AFCTEE (1-azido-formic acid 1,1,1-trinitro-ethyl ester)

To explore new high-energy azido nitro compounds as plasticizers for propellants, AFCTEE (1-azido-formic acid 1,1,1-trinitro-ethyl ester) was designed and studied using density functional theory. The predicted density of AFCTEE, 1.90 gcm−3, is comparable to that of HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane) and much higher than that of general organic azido compounds. AFCTEE possesses higher energetic properties and chemical stability than the promising azido nitro plasticizer DAMNP (1,3-diazido-2-methyl-2-nitropropane) and the conventional plasticizer NG (nitroglycerine), and it has a moderate thermal stability. The pyrolysis of AFCTEE starts from the rupture of C–NO2 and then the breakage of N–N2 via Curtius rearrangement. This work is the initial exploration for AFCTEE, aiming at the energetics, spectra (IR, NMR, and UV), stability, and decomposition mechanism. Compared with DAMNP, the advantages of superior energetic properties and chemical stability suggest AFCTEE is a promising energetic azido nitro compound and is worth further investigation.

A theoretical study on the stability and intramolecular interaction in 5-nitrotetrazolates with the DFT and DFT-D methods

Two new salts 3,5-diazido-1,2,4-triazolium 5-nitrotetrazolate and 1-methyl-3,5-diazido-1,2,4-triazolium 5-nitrotetrazolate were designed based on the structures of experimentally synthesized 3-azido-1,2,4-triazolium 5-nitro-tetrazolate and 1-methyl-3-azido-1,2,4-triazolium 5-nitro-tetrazolate, to explore new promising candidates for energetic materials and to investigate the influences of the substituents (- CH 3 and - N 3) and solvent (water) on the intramolecular interactions and properties. The intramolecular hydrogen bonding interactions were investigated by the natural bond orbital (NBO) and the quantum theory of atoms in molecules (QTAIM) analyses using the density functional theory (DFT) and the dispersion correction DFT (DFT-D) methods. The low-lying singlet electronic transitions were estimated using the time-dependent DFT. All four examined salts exist as ionic structures in aqueous solution while acid–base molecular complexes form in gas phase. The hydrogen bond energy (E H ) obtained with the DFT-D method is larger than that obtained with the DFT method, but the trend is consistent, i.e. - N 3 increases while - CH 3 decreases E H . In addition, the position of the strongest electronic absorption peak has a little correlation with the number of - N 3 and - CH 3 groups. 3,5-diazido-1,2,4-triazolium 5-nitrotetrazolate is a valuable energetic salt with the highest nitrogen content, oxygen coefficient and density and the second highest heat of formation and chemical stability.