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

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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.