Substituent Effects on Thermodynamic and Detonation Properties of Polynitrobenzenes

Abstract

Density functional theory (DFT) calculations were performed for a series of polynitrobenzene derivatives. Some nitrobenzenes with amino groups attached were also investigated as a benchmark or as a precursor. Heats of formation (HOF) were evaluated. The isodesmic reactions used for the prediction of HOFs are of permutation type in terms of the substituents. The HOFs increase non‐additively with increasing number of nitro groups. The attachment of the amino groups to polynitrobenzenes dramatically decreases the HOF. The HOF of hexanitrobenzene (HNB) is 344.05 kJ mol−1 at the B3LYP/6‐311+G** level. This value is much larger than that of the widely used 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB), which engenders HNB a large chemical energy of detonation. The strengths of the group interactions were analyzed according to the disproportionation energy. The nearest‐neighbor interactions in polynitrobenzenes are in the range of 27.20–55.90 kJ mol−1. The energy barrier for the internal rotation of nitro group in nitrobenzene is 24.6 kJ mol−1. However, the energy barrier for the internal rotation of 2‐position nitro group of 1,2,3‐trinitrobenzene is as large as 216.3 kJ mol−1. The chemical energies of detonation for polynitrobenzenes with three or more nitro groups are over 6000 J g−1. Pentanitroaniline and HNB have good performances in terms of detonation velocity and pressure.

Use of G4 Theory for the Assessment of Inaccuracies in Experimental Enthalpies of Formation of Aromatic Nitro Compounds

“…The enthalpies of formation of nitro compounds were calculated earlier by different quantum chemical composite and DFT methods using the standard atomization reaction procedure and isodesmic reaction method. − In our previous work, it was revealed that the G4 method, one of the most successful and widely used composite methods, underestimates the Δ f H 298 ° (g) values for most nitro compounds by up to 20 kJ·mol –1 . Therefore, reliable results cannot be expected when using the atomization reaction.…”

Carbonyl-bridged energetic materials: biomimetic synthesis, organic catalytic synthesis, and energetic performances

“…Meanwhile, a simple method, developed by Pang et al on the basis of the empirical Kamlet formula, was employed to calculate the heats of detonation of some metal-containing explosives (see ESI †). 58 The results showed Q for compound 1 to be 2.28 kcal g −1 , higher than those of most commonly used explosives, [59][60][61] including hexanitrohexaazaisowutzitane (CL-20; about 1.5 kcal g −1 ) 59,62 and octanitrocubane (ONC; 1.8 kcal g −1 ), 63 the two most powerful organic explosives known to date (see Chart 1). The findings imply that bridging carbonyl group is an effective and important energetic linker for constructing high-performance energetic materials with improved density, improved OB, suitable thermostability, high heat of formation and high energy.…”