FOX-12制备过程的反应机理及动力学

Mechanisms and Kinetics of the Synthesis of FOX-12

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。

The mechanisms of the synthesis of N-guanylurea-dinitramide （FOX-12） were investigated at B3LYP/6-311 G（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 binitroamide acid（HDN） could be obtained by both channel Al, in which -SO3 was preferentially replaced by nitronium（ NO2^＋） , and channel B, in which -H was preferentially replaced by NO2^＋, while the channel Al 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.