New aspects of initiation reactivities of energetic materials demonstrated on nitramines

A brief survey is presented of the author's results obtained from studies of the chemical micro-mechanisms of nitramines initiation from the point of view of organic chemistry. The relationships have been presented and discussed between the characteristics of impact and electric spark sensitivities, detonation and thermal decomposition, on the one hand, and 15N NMR chemical shifts of nitrogen atoms of nitramino groups, on the other. In the case of the impact sensitivity, the said relationships involve the 15N shifts of the amino nitrogen atoms carrying the nitro group primarily split off from the molecule. In the case of the initiation by shock, heat and electric spark, the 15N shifts of nitrogen atoms in the primarily split off nitro groups themselves are involved. Also, the relationships are presented between the characteristics of thermal reactivity and values of the electronic charges at the nitro groups that are primarily split off. It has been stated that the chemical micro-mechanisms of primary fission processes of molecules of nitramines in the initiation by mechanical stimuli (inclusive the detonation course) and electric spark should be the same as in the case of their low-temperature thermal decomposition. It has been found that the electron structure and close neighbourhood of nitrogen atom of the primarily leaving nitro group is a dominant factor in initiation by shock, electric spark and heat. In the case of initiation by impact a key role plays characteristics of amino nitrogen atoms which are carriers of these most reactive nitro groups. Also mentioned is relevance of the modified Evans-Polanyi-Semenov relationship. On the basis of the findings presented it also has been stated that the detonation transformation itself of the nitramines should be preceded by an induction period.