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Electric Spark Sensitivity of Nitramines. Part I. Aspects of Molecular Structure

100%

Zeman S. , Pelikán W. , Majzlík J. , Friedl Z. , Kočí J.

tom Vol. 3, nr 3

27-44

An ESZ KTTV instrument of a new, relatively simple construction has been applied to determination of electric spark sensitivity (EES) of 16 nitramines. Results obtained are compared with those from measurements by means of an older RDAD instrument. Attention was focused both on the relationships between the EES values from both the instruments and theoretical B3LYP/6-311+G(d,p) N-NO2 bond dissociation energies, B3LYP/6-31G(d,p) Mulliken net charges of the nitro group, heats of fusion and 15N NMR chemical shifts of the nitrogen atoms of the most reactive nitro groups, respectively. It is stated a larger difference between results of both instruments. The EES values from both the instruments correlate with such characteristics of molecular structure which correspond to the primarily leaving nitro group in the nitramine molecule. It has been found that these relationships for ESZ KTTV results are strongly affected by molecular structure factors. It is also pointed out that the dislocations in the crystals should have some relation to electric spark sensitivity.

N-N Bond Lengths and Initiation Reactivity of Nitramines

75%

Zeman S. , Atalar T. , Růžička A.

tom Vol. 17, no. 2

169--200

For the 16 selected nitramines, it is shown that an increase in the energy content of these molecules (represented by enthalpies of formation) is connected with an increase in the lengths of the longest N–N bonds in the molecules. These lengths are directly proportional to the activation energies of the low-temperature thermal decomposition of the pure nitramines in all states of matter for this reaction. Raising the energy content also leads to reductions in the rate constants of thermal decomposition. Both of these facts are in contrast to expectations and also with similar published findings concerning thermal decomposition of nitramines in solution, which can be explained by the solvation effect and termination of the emerging aza-radicals in solutions. The calculated dissociation energies of the weakest N–N bonds yielded a relatively good reciprocal conformity with the lengths of the longest N–N bonds of the nitramines studied, especially when using the UB3LYP/6-31G* method. The relationship between the impact sensitivity of these nitramines and the lengths of their longest N–N bond is not completely clear. Such lengths cannot be a measure of impact reactivity, because the longest N–N bond might be stabilized in some cases by suitable intermolecular interactions with adjacent molecules in the crystal lattice.