A new look on the electric spark sensitivity of nitramines

Electric spark energy, EES, for a 50% probability of initiation of the 14 nitramines was determined using a measuring instrument in which the electrodes are in direct contact with the sample. Indirectly proportional relationships were established between the logarithm of the EES values and the length of the longest N–N bond in the nitramine molecule. This finding is compatible with the mechanism of the first step in the electro-reduction of the nitramine grouping. Directly proportional relationships were found to exist between the EES values and the crystal lattice free volumes, ΔV (i.e. an increase in the ΔV values increases the nitramine's resistance to electric sparks) but there were several nitramines with the opposite course of this relationship. Also a semilogarithic relationships between the EES values and a ratio of intrinsic volumes of molecule, Vint, to the ΔV values were described as well as ambiguous linear dependence between these energies and a sum of the positive and negative extremes of the molecular surface electrostatic potentials, VS,Σ. Several nitramines studied (always the same ones) display roughly the same distribution in the coordinate systems of relationships with lengths of the longest N–N bonds, the Vint/ΔV ratio and the sum VS,Σ as the independent variables. It was found that, typically, such relationships start from a single identical point, in effect a point corresponding to data for a structural unit from which the studied nitramines can be hypothetically generated, and/or are converging on another point, often the one corresponding to the data for HNIW. All the findings point to a fundamental influence of the intermolecular forces on reactivity of nitramines exposed to electric sparks. Relationship between electric spark sensitivity, expressed as energy of electric spark EES, and crystal lattice free volume, ΔV, of the studied nitramines. [Display omitted] •The electric spark energy corelate with length of the N-N bonds, the crystal lattice free volume, ΔV, and with the ratio of instristic volumes / ΔV.