Impact of Positional Isomerism on Melting Point and Stability in New Energetic Melt-Castable Materials

For an energetic material with a definite composi-tion, the substituent position is the most crucial factor to influence its physicochemical properties. Thus, it is becoming increasingly important to understand the impact of positional isomerism on multidimensional properties differences. Herein, we reported two new potential energetic melt-castable molecules, a pair of positional isomers (4-MMDNP and 5-MMDNP). These two explosives exhibit obviously different properties, including densities ( Delta rho = 0.03 g cm-3), melting point (Delta Tm = 47.2 degrees C), decomposition temperature (Delta Td = 27.3 degrees C), stability (IS = 20 J, FS = 160 N vs IS = 10 J, FS = 40 N), etc., even though they share similar compositions and structures. Simultaneously, by analyzing crystal packing, intermolecular interactions, and monomolecular parameters, we were able to uncover the roots of property differences. Altogether, our results provide comprehensive molecular and crystal level insight into the effect of positional isomerism, which may be useful for new molecular design.

Automated summary

For an energetic material, the position of substituents plays a crucial role in determining its physicochemical properties. This study focused on the impact of positional isomerism on two new potential energetic melt-castable molecules, 4-MMDNP and 5-MMDNP. Despite having similar compositions and structures, these explosives exhibited significant differences in properties such as density, melting point, decomposition temperature, and stability. By analyzing crystal packing and intermolecular interactions, the reasons for these property differences were uncovered. These findings provide valuable insights for the design of new molecules.