Comparative Theoretical Studies of Energetic Azo s-Triazines

Abstract

In this work, the properties of the synthesized high-nitrogen compounds 4,4',6,6'-tetra(azido)azo-1,3,5-triazine (TAAT) and 4,4',6,6'-tetra(azido)hydrazo-1,3,5-triazine (TAHT), and a set of designed bridged triazines with similar bridges were studied theoretically to facilitate further developments for the molecules of interests. The gas-phase heats of formation were predicted based on the isodesmic reactions by using the DFT-B3LYP/AUG-cc-PVDZ method. The estimates of the condensed-phase heats of formation and heats of sublimation were estimated in the framework of the Politzer approach. Calculation results show that the method gives a good estimation for enthalpies, in comparison with available experimental data for TAAT and TAHT. The crystal density has been computed using molecular packing calculations. The calculated detonation velocities and detonation pressures indicate that -NF(2), -NO(2), -N═N-, and -N═N(O)- groups are effective structural units for improving the detonation performance of the bridged triazines. The synthesized TAAT and TAHT are not preferred energetic materials due to their inferior detonation performance. The p→π conjugation effect between the triazine rings and bridges makes the molecule stable as a whole. The electrostatic behavior of the bridged triazines is characterized by an anomalous surface potential imbalance when incorporating the strongly electron-withdrawing -NF(2) and -NO(2) groups into the molecule. An analysis of the bond dissociation energies shows that all these derivatives have good thermal stability over RDX and HMX, and the -NH-NH- bridge is more helpful for improving the stability than -N═N(O)- and -N═N- bridges. Considering the detonation performance and thermal stability, three bridged triazines may be considered as the potential candidates of high-energy density materials (HEDMs).

Preparation, morphologies and thermal behavior of high nitrogen compound 2-amino-4,6-diazido-s-triazine and its derivatives

“…However, there is an obvious melting process for TAAT at about 152 °C before decomposition covered by an enthalpy of fusion 93-100 J. , respectively, which are lower than that of C-N 3 (366-370 kJ mol -1 ) bond [37]. It was found that the bond order of C-N 3 and C-R' (R' denotes groups N=N and NH-NH) bonds are much smaller than those of C-N bonds, which indicates that the trigger linkage in the compounds appears to be C-N 3 or C-R' bond [38]. For the TAHT, the C-N 3 bonds have the lowest bond order, so they are easier to break than other bonds according to the principle of the smallest bond order (PSBO) [39].…”

“…When two DAAT molecules are combined by hydrazo or azo bridge (-NH-NH-or -NH=NH-) forming TAHT and TAAT, their thermal stability and heat of decomposition are slightly lower than DAAT. It has been found that the hydrazo in TAHT desensitize this compounds and decrease its volatility, which results in a non-observable melting point up to their fast decomposition at 202 °C [38]. However, there is an obvious melting process for TAAT at about 152 °C before decomposition covered by an enthalpy of fusion 93-100 J. , respectively, which are lower than that of C-N 3 (366-370 kJ mol -1 ) bond [37].…”

First principles prediction of an insensitive high energy density material

“…31 and 33, are shown in Table 2. 7b, 39 The isodesmic reaction used in this study is outlined in Fig. An alternative approach for calculating gas phase heat of formation is to use isodesmic reactions.…”

Exploring aliphatic nitro azides for plasticizers: a combined DFT and MD investigation

“…31,32 The molecular packings of M2 with the lowest energy in their respective space group are collected in Table 5. The polymorph of M2 was predicted by searching the molecular packings among seven most possible space groups (C2/c, P2 1 , P2 1 /C, P 1, P2 1 2 1 2 1 , Pbac, and Pna2 1 ) using the Dreiding force eld and the Polymorph module.…”