FOX-12制备过程的反应机理及动力学

采用量子化学计算方法, 在B3LYP/6-311G(d,p)水平上研究了N-脒基脲二硝基酰胺盐(FOX-12)制备过程的反应机理. 优化得到了反应势能面上各稳定点的几何构型, 通过内禀反应坐标(IRC)确认了反应物、 中间体、 过渡态及产物之间的相关性. 为了得到更可靠的反应能量和势能面信息, 进一步在MP2/6-311++G(3df,3pd)水平上对得到的构型进行能量校正, 结果表明, 先取代磺酸基通道(A1)和先取代氢通道(B)都能生成二硝基酰胺酸(HDN), 其中通道A为主反应通道; HDN可以通过HDN→FOX-12与HDN→ADN→FOX-12 两种途径转化为目标产物FOX-12, 而第2种途径为较优途径. 应用经典过渡态理论(TST)与变分过渡态理论(CVT)以及小曲率隧道效应模型校正的变分过渡态理论(CVT/SCT)计算了在200~400 K范围内各反应通道相关基元反应的速率常数, 提供了在上述温度区间内的三参数Arrhenius关系式.

Mechanisms and Kinetics of the Synthesis of FOX-12†

The mechanisms of the synthesis of N-guanylurea-dinitramide(FOX-12) were investigated at B3LYP/6-311G(d,p) level. The geometries of the reactants, intermediates, transition states, and products were optimized, respectively. The relevance between every transition state and the corresponding reactant/product was confirmed via the intrinsic reaction coordinates(IRC). The single-point energies of the species at the optimized geometries were corrected at the MP2/6-311++G(3df,3pd) level. It was shown that the binitro-amide acid(HDN) could be obtained by both channel A1, in which —SO₃ was preferentially replaced by nitronium(N\begin{array}{c}{O}_2^{+}\end{array}), and channel B, in which —H was preferentially replaced by N\begin{array}{c}{O}_2^{+}\end{array}, while the channel A1 was found to be the dominant channel. Then the intermediate product of HDN could be converted to the targeted product of FOX-12 via the channel of either HDN→FOX-12 or HDN→amonium dinitramide(ADN)→FOX-12, while the latter was tend to be considered as the better approach. The rate constants were calculated at temperature ranges of 200—400 K by means of the classical transition state theory(TST) and the canonical vibration transition state theory(CVT) corrected by the small-curvature tunneling(SCT). And the three-parameter Arrhenius expressions of rate constants were also provided. It was expected that the present study may provide a theoretical basis to the research and engineering amplification of FOX-12 as well as other energetic materials.