Comparison with Molecular Surface Electrostatic Potential and Thermal Reactivity of Nitramines

Molecular surface electrostatic potentials VS（r） （ ESP） of seventeen nitramines have been calculated. As a criterion of the imbalance between the maximum positive,VS,max and minimum negative,VS,min,values of molecular surface electrostatic potentials their sum was derived and used as a new simple characteristic for ESPs-VS,Σ. These VS,Σ values have close relationships with the Arrhenius parameters,activation energy Ea and preexponent log A,of thermal decomposition of the nitramines studied. The correlation between the VS,Σ values and heats of fusion of the nitramines studied is described. These findings suggested analyzing the physico-chemical behavior of the nitramine crystals during this decomposition; in this connection an investigation was carried out using isothermal thermogravimetry and scanning electron microscopy of thermally exposed crystals of cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole（ sintering of its crystal surfaces）,of β-1,3,5,7-tetranitro-1,3,5,7-tetrazocane（ cracking of its crystals during β !δ transition） and of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane. The results suggest a need to study the pre-decomposition states on thermal decomposition of the nitramines' molecule's crystals.