ANOMALOUS ENERGY EFFECTS IN SOME ALIPHATIC AND ALICYCLIC AZA SYSTEMS AND THEIR NITRO-DERIVATIVES

We have used an ab initio SCF molecular orbital approach in conjunction with the isodesmic reaction procedure to investigate anomalous energy effects in aliphatic and alicyclic aza systems. These molecules are found to be significantly stabilized, which we attribute to -conjugation of the nitrogen lone pairs; these are presumably delocalized to some extent through the -bond framework. The stabilization increases with the number of nitrogens in a series of similar molecules and is greater in cyclic systems, particularly when rings are fused. The magnitudes of the most negative electrostatic potentials of the aza nitrogens, which can be viewed as indicating the degrees of delocalization of the nitrogen lone pairs, decrease as the added stability increases. In these systems, the introduction of nitro groups also has an overall stabilizing effect, which may be due to further delocalization of -electrons, reflecting the strong electron-withdrawing power of the nitro group. 1990 American Chemical Society.

ANOMALOUS ENERGY EFFECTS IN SOME ALIPHATIC AND ALICYCLIC AZA SYSTEMS AND THEIR NITRO-DERIVATIVES Academic Article