环脲硝胺化合物的性能和电子结构之间的关系II. 水解安定性

环脲硝胺单质炸药具有密度大、能量高、爆速快等优点,但容易水解。水解安定性如何成为它们能否被实际应用或广泛应用的关键问题。文献1]和2]实测了系列该类化合物的水解速度常数,并从分子结构和理论有机传统观点分析了它们水解安定性的递变原因,推测了它们的水解机理.为从电子微观层次上研究该类化合物结构与性能之间的规律联系,我们用SCF-CNDO/2全价电子半经验方法进行计算,找到它们的羰基伸缩振动频率与计算参量之间的线性关系。考虑到计算结果对构型、构象的敏感依赖关系,所以将11个文献物分为具单、双和三环三类进行了仔细的优化计算,发现其水解安定性与分子中羰基C上正电荷有关,且受空间位阻效应影响很大。

The Relations Between Properties and Electronic Structure of Cyclourea Nitroamine Compounds II. Hydrolytic Stability

The eleven title compounds are classified into three series according to their molecular structure having mono-, bi- and tri-condensed ring system, respectively. For each series the hydrolytic stabilities decrease with the increase of the calculated CNDO/2 net positive charge on C atom of carbonyl group. This relation supports the kinetic hydrolysis mechanism, in which the hydrolysis reaction is initiated by the nucleophylic attack on the C atom of the carbonyl group. It can be applied to predict the relative stsbility of some cyclourea nitroamines by means of similar theoretically calculated parameters. For bi- and tri-condensed ring compounds, which have V- and U-type optimized configurations respecively, the steric hindrance due to the C=O group covering large —CH_2C(NO_2)_3 group plays an important role also, especially for the V-type bi-condensed ring compounds.