A Facile Method for Assessing the Change in Detonation Properties during Chemical Functionalization: The Case of NH₂→NHNO₂ and NH₂→=N⁺=N^– Conversions

A simple and fast procedure for estimation of the effect of chemical functionalization on the change in detonation properties of energetic materials is reported. The procedure consists of two levels: the first level is the calculation based on atomic increments and can be performed with a pocket calculator. This level indicates a pool of possible chemical structures, which can be significantly improved in detonation properties by the given chemical transformation. At the second level, quantum-chemical calculations provide accurate estimates of the change in detonation properties taking into account exact chemical structures. Quantum-chemical calculations at Level 2 are aimed to obtain crystalline density (d_c) and solid-state enthalpy of formation (ΔH_f) and include the following sequence of computational tasks: vacuum-isolated molecule relaxation (PBE/DND) → crystal structure prediction (COMPASSII) → crystal cell relaxation (PBE/DND). The method is well-calibrated on the available experimental data providing high regression qualities (R² > 0.9) and is reliable. Thus, we have analyzed transformation of both aromatic and aliphatic amines into the corresponding nitramines and diazo compounds. The calculations at Level 1 indicate that both d_c and ΔH_f are always positive and increase detonation properties, while the calculations at Level 2 indicate the specific amines, which are the most sensitive to such chemical transformation, whose detailed description is presented in the full paper.