Crystal lattice free volume and thermal decomposition of nitramines

Abstract

The linear, directly proportional, equations between the Arrhenius parameters (Ea and log A) of the thermal decomposition and the crystal lattice free space per molecule, ΔV, of 22 nitramines are described. It is shown that, because of a significant limitation by the molecular structural characteristics of such compounds, they are divided into a number of partial relationships. These partial relationships divide the nitramines into a group of substances relating to dimethyl nitramine and a sub-group related to ε−HNIW. These directly proportional equations mean that an increase in the ΔV values is related to an increase in the thermal stability of the corresponding nitramines. A comparison with similar published dependencies for the impact and friction sensitivities, on the one hand, and with the relationship between the Ea values and the sum of the negative and positive extremes of molecular surface electrostatic potentials, on the other, confirms the well-known fact that intermolecular interaction in the nitramines studied plays a decisive role in the thermal reactivity of such compounds. The crystal lattice free space manifests itself here perhaps only in the solid state thermal decomposition of RDX, HMX and DINGU. This study again confirms a level of disorder in the distribution of the forces in the crystal lattice of the “common” quality of ε−HNIW, compared with its “reduced sensitivity (RS)” or pure analogues.