A theoretical investigation on the structures, densities, detonation properties and pyrolysis mechanism of the nitro derivatives of toluenes

The nitro derivatives of toluenes are optimized to obtain their molecular geometries and electronic structures at the DFT-B3LYP/6-31G* level. Detonation properties are evaluated using the modified Kamlet-Jacobs equations based on the calculated densities and heats of formation. It is found that there are good linear relationships between density, detonation velocity, detonation pressure and the number of nitro and methyl groups. Thermal stability and the pyrolysis mechanism of the title compounds are investigated by calculating the bond dissociation energies at the unrestricted B3LYP/6-31G* level. The activation energies of H-transfer reaction are smaller than the BDEs of all bonds and this illustrates that the pyrolysis of the title compounds may be started from the isomerization reaction of H transfer. According to the quantitative standard of energetics and stability as an HEDC (high energy density compound), pentanitrotoluene essentially satisfies this requirement. In addition, we have discussed the effect of the nitro and methyl groups on the static electronic structural parameters and the kinetic parameter.