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

At the molecular level, the ground-state intrinsic energies of the C-N O2 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 anothe r using their theoretical optimized geometries. Their enthalpies of fo rmation have been calculated using a modified X alpha approach and, fi nally their explosive characteristics have been studied at the macrosc opic level with the help of the thermodynamic code of Kondrikov-Sumin. With respect to the planar mononitro derivative, the second nitration provokes, (i) a torsion of about 30 degrees of the two nitro groups, (ii) a significant lowering of the C-N bond dissociation energy, by ab out 9 kcal mol(-1), together with a weakening of the N-N bonds thus re ducing thermostability, (iii) an increase of the C-NO2 and N-N bond po larities in the electronic excited states, correlated with a lowering of shock sensitivity, and (iv) an increase of the gas-phase enthalpy o f 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 describ e the ideal velocity of detonation D-CJ as a function of the density r ho(0) by D-CJ = 0.337 + 3.86 rho(0) and D-CJ = 2.246 + 3.61 rho(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 densit y of 1.6 g cm(-3).