Comparison with Molecular Surface Electrostatic Potential and Thermal Reactivity of Nitramines

Molecular surface electrostatic potentials V_S(r) ( ESP) of seventeen nitramines have been calculated. As a criterion of the imbalance between the maximum positive,V_(S,max) and minimum negative,V_(S,min),values of molecular surface electrostatic potentials their sum was derived and used as a new simple characteristic for ESPs-V_(S,Σ). These V_(S,Σ) values have close relationships with the Arrhenius parameters,activation energy E_a and preexponent log A,of thermal decomposition of the nitramines studied. The correlation between the V_(S,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.

Molecular surface electrostatic potentials Vs（r） （ESP） of seventeen nitramines have been calculated. As a criterion of the imbalance be- tween 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,∑. These Vs,∑ 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.∑ 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/3-1,3,5,7-tetr anitro-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.