A theoretical investigation into the strength of N–NO 2 bonds, ring strain and electrostatic potential upon formation of intermolecular H-bonds between HF and the nitro group in nitrogen heterocyclic rings C n H 2 n N–NO 2 ( n = 2–5), RDX and HMX

Changes in N–NO 2 bond strength, ring strain energy and electrostatic potential upon formation of intermolecular H-bonds between HF and the nitro group in nitrogen heterocyclic rings C n H 2 n N–NO 2 ( n = 2–5), RDX and HMX were investigated using DFT-B3LYP and MP2(full) methods with the 6-311++G(2df,2p) and aug-cc-pVTZ basis sets. Analysis of electron density shifts was also carried out. The results indicate that H-bonding energy correlates well with the increment of ring strain energy. Upon complex formation, the strength of the N–NO 2 trigger-bond is enhanced, suggesting reduced sensitivity, while judged by the increased ring strain energy, sensitivity is increased. However, some features of the molecular surface electrostatic potential, such as a local maximum above the N−NO 2 bond and ring, σ + 2 and electrostatic balance parameter ν, remain essentially unchanged upon complex formation, and only a small change in the impact sensitivity h 50 is suggested. It is not sufficient to determine sensitivity solely on the basis of trigger bond or ring strain; as a global feature of a molecule, the molecular surface electrostatic potential is available to help judge the change of sensitivity in H-bonded complexes. Graphical Abstract The strengthened N–NO 2 bond suggests reduced sensitivity, while it is reverse by theincreased ring strain energy upon the complex formation. However, the molecular surfaceelectrostatic potential ( V S ) shows the little change of h 50 . The V S should be taken into accountin the analysis of explosive sensitivity in the H-bonded complex.