Correlation Between Molecular Charge Properties and Impact Sensitivity of Explosives: Nitrobenzene Derivatives

Nitrobenzenic explosives can have high energy density and low impact sensitivity. In this work, the density functional theory (DFT) charge density of 50 nitrobenzenic molecules was analyzed using the Distributed Multipole Analysis (DMA) method to investigate the impact sensitivity of their explosives. The DMA monopole, dipole and quadrupole electric multipoles localized on the atoms of a molecule provide a very detailed picture of the molecular charge density and have a clear chemical interpretation. The DMA multipoles of each molecule were used to develop models correlating molecular charge properties and impact sensitivity of nitrobenzenic explosives, which is quantified by the quantity h(50). Three models previously applied to 17 nitroaromatic molecules (J. Phys. Chem. A 115, 9055, 2011) are now examined for a larger dataset of 50 molecules. Model 1 used the nitro group charge as a single parameter for h(50) prediction, Model 2 additionally included the quadrupole values of the benzene ring atoms (a measure of charge delocalization) and Model 3 included the dipole moment (indicator of site polarization) of the nitro groups of each molecule, as well as the average C-NO2 bond distance, which quantifies bond strength. Two additional new models that include the quadrupole values of the nitro group were also proposed. The original three models (Models 1-3), as well as the new models (4-5), applied to the set of 50 nitrobenzenic molecules, displayed good results even when compared with the previous work. Among the computed DMA electrical multipole values, two proved to be essential for developing a good model, as found before for the smaller set: the DMA quadrupole values of the ring atoms that quantify the degree of electronic delocalization in the ring and the total DMA charge (monopole) values of the explosophore nitro group.

Automated summary

In this study, the charge density of 50 nitrobenzenic molecules was analyzed using the DMA method to investigate their impact sensitivity. Several models were developed to correlate molecular charge properties with impact sensitivity, with good results obtained for the larger dataset of 50 molecules. Key multipole values were identified as important factors in developing accurate predictive models for nitrobenzenic explosives.