Theoretical analysis of the effects of nitration of the explosive properties of triazoles: 4-nitro-2H-1,2,3-triazole and 4,5-dinitro-2H-1,2,3-triazole

Abstract At the molecular level, the ground-state intrinsic energies of the CNO 2 and NN bonds and the excited-state bond polarities of the 4-nitro- and 4,5-dinitro-2H-1,2,3-triazoles have been compared with one another using their theoretical optimized geometries. Their enthalpies of formation have been calculated using a modified Xα approach and, finally their explosive characteristics have been studied at the macroscopic level with the help of the thermodynamic code of Kondrikov-Sumin. With respect to the planar mononitro derivative, the second nitration provokes, 1. (i) a torsion of about 30 ° of the two nitro groups 2. (ii) a significant lowering of the CN bond dissociation energy, by about 9 kcal mol −1 , together with a weakening of the NN bonds thus reducing thermostability 3. (iii) an increase of the CNO 2 and NN bond polarities in the electronic excited states, correlated with a lowering of shock sensitivity, and 4. (iv) an increase of the gas-phase enthalpy of formation from − 25 kcal mol − 1 (or − 51 kcal mol − 1 , estimated for the condensed phase) for the mononitro derivative to + 65 kcal mol − 1 (viz. + 50 kcal mol −1 for the dinitro compound. Using these enthalpy results and a Kondrikov-Sumin-like equation of state, one can describe the ideal velocity of detonation D CJ as a function of the density ρ 0 by D CJ = 0.337 + 3.86 ρ 0 and D CJ = 2.246 + 3.61 ρ 0 for the mononitro and dinitro derivatives, respectively, thus giving the corresponding velocities of 6.5 and 8.0 km s −1 for an assumed density of 1.6 g cm −3 .