Impact of regioisomerism on unimolecular decomposition reactions of energetic materials: Quantum chemistry modeling of ICM-103 and NAPTO

Abstract

Energetic regioisomers usually behave different physicochemical properties, and the thermal decomposition mechanism might also be different. In this work, the unimolecular decomposition reactions of two novel energetic isomers, ICM-103 and NAPTO, were investigated through quantum chemistry calculations to reveal the decay mechanism of energetic regioisomers. The molecular properties were first explored to reveal their differences in the molecular properties of ICM-103 and NAPTO. Then, six initial decomposition channels were obtained, including N2 release of azide group, H transfer, O transfer, nitro dissociation, nitro-nitrite isomerization, and ring-opening reaction. Thermochemistry results show that the most possible decay reaction is the cleavage of NN bonds of azide group to generate N2, and the energy barrier of ICM-103 is lower than that of NAPTO, which is consistent with the conclusion that NAPTO is more stable form the experiment. Specially, two molecules react differently, and a sequential N2 loss is expected in one, and N2O loss in the other is almost lost in the clutter. Besides, the nitro dissociation, nitro-nitrite isomerization, and ring-opening reaction energy of ICM-103 are also lower than that of NAPTO. However, for the other same reaction, the energy barrier of ICM-103 is higher than that of NAPTO. These findings in the initial decomposition pathways of ICM-103 and NAPTO could gain more understanding of the effect of regiochemical control on the thermal stability of energetic materials.