Theoretical investigation into the solvent effect on the thermal decomposition of RDX in tetrahydrofuran, acetone, toluene, and benzene.

Fu-De Ren,Xiong Cao,Yu-Tong Cui

doi:10.1007/s00894-021-04966-z

Fu-De Ren, Xiong Cao + Show 1 more

Open Access

https://doi.org/10.1007/s00894-021-04966-z

Copy DOI

Abstract

In order to clarify the solvent effect on the thermal decomposition of explosive, the N-NO2 trigger-bond strengths and ring strains of RDX (cyclotrimethylenetrinitramine) in its H-bonded complexes with solvent molecules (i.e., tetrahydrofuran, acetone, toluene, and benzene), and the activation energies of the intermolecular hydrogen exchanges between the solvent molecules and C3H8O2N4 or CH4O2N2, as the model molecule of RDX, were investigated by the BHandHLYP, B3LYP, MP2(full), and M06-2X methods with the 6-311 + + G(2df,2p) basis set, accompanied by a comparison with the calculations by the integral equation formalism polarized continuum model. The solvent effects ignore the ring strain while strengthening the N-NO2 bond, leading to a possible decreased sensitivity, as is opposite to the experimental results. However, the activation energies are in the order of C3H8O2N4/CH4O2N2∙∙∙acetone < C3H8O2N4/CH4O2N2∙∙∙THF < C3H8O2N4/CH4O2N2∙∙∙toluene < C3H8O2N4/CH4O2N2∙∙∙benzene < C3H8O2N4/CH4O2N2, suggesting that the order of the critical explosion temperatures might be RDX∙∙∙acetone < RDX∙∙∙THF < RDX∙∙∙toluene < RDX∙∙∙benzene < RDX, as is roughly consistent with the experimental results. Therefore, the intermolecular hydrogen exchange with the HONO elimination is a possible mechanism of the solvent effect on the initial thermal decomposition of RDX. The solvent effect on the sensitivity is analyzed by the surface electrostatic potentials.

Highlights

With the development of science and military technology, both belligerents always strive to destroy each other's military powers with the most advanced equipments
By ab initio and density functional theory (DFT) methods, Habibollahzadeh et al [11] found that a competitive reaction occurred between the symmetrical ring-opening reaction and N‒NO2 bond dissociation, with the formation of three methylene nitramines, which was consistent with the experimental result by Liu et al [3]
Wu et al [12] calculated the bond dissociation energy (BDE) of the N‒NO2 bond and the ring-opening energy of the symmetric ring-breaking by DFT, and concluded that the dissociation pathway of the N‒NO2 bond was the main pathway of the decomposition reaction, which was consistent with the semi-empirical PM3 calculation by Pivina et al [13]

Summary

Introduction

With the development of science and military technology, both belligerents always strive to destroy each other's military powers with the most advanced equipments. In order to reveal the essence of the solvent effect on the initial thermal decomposition of RDX, in this work, the changes of the N–NO2 bond strengths and ring strains upon the formation of the intermolecular interactions between RDX and solvent molecules THF, acetone, toluene or benzene, as well as the activation energies of the intermolecular hydrogen exchange reactions (leading to the possible HONO elimination) between the model molecule of RDX and above solvent molecules were investigated.

Results

Conclusion