1,3-INTERACTION BETWEEN AMIDE NITROGENS------Possibility and Limitation

本研究的目的是探索酰胺型氮原子之间可能的1，3-相互作用。1，3，5-三苯甲酰基全氢-1，3，5-三嗪（A）是最合适的体系，X射线晶体学分析表明，该分子是对称的，氮原子具有近似的三角结构。这意味着所涉及的氮是常规的酰胺氮，这与1，2-二酰基肼中的四面体氮相反。虽然没有发现酰胺氮之间的1，3-相互作用，但我们对（A）的C-13 NMR谱进行了变温研究。随着温度的降低，观察到对应于酰胺旋转的线形变化。随着温度进一步降低，观察到第二次化学交换。这种速率过程很可能是由于氮转化造成的。不幸的是，NMR光谱仪一般不能达到低于-100 ℃的温度，因此我们未能最终解释。总之，在（A）中，氮原子可能在某种程度上具有四面体特征。这可能意味着酰胺氮之间确实存在1，3-相互作用。要最后确定这一结论还需要进一步的研究。因此，我们未能最终确定我们的解释。

The purpose of this investigation is to explore the possible 1,3- interaction between amide-type nitrogen atoms. It seems that 1,3,5- tribenzoylperhydro-1,3,5-triazine(A) is the most appropriate system for this purpose.The X-ray crystallographic analysis of (A) revealed that the molecule is symmetric and the nitrogen atoms have approximate trigonal structures. This means that the nitrogen involved is a conventional amide nitrogen, which is in contrast to the tetrahedral nitrogen in 1,2-diacylhydrazine. The results were already published in Acta Cryst.Though no indication of 1,3-interaction between amide nitrogens, we explored variable temperature of C-13 NMR spectra of (A). As the temperature lowered, there was observed a change of line-shape which corresponds to the amide rotation. As the temperature further lowered, there was observed the second chemical exchange. This rate process is most likely due to the nitrogen inversion. Unfortunately the NMR spectrometer in general cannot reach temperature below-100C and hence we failed to finalize our interpretation.In conclusion, it is likely that in (A) the nitrogen atoms have a tetrahedral character to some extent. This might mean that the 1,3-interaction between amide nitrogens do exist. Further study would be required to finalize this conclusion.;C and hence we failed to finalize our interpretation.