[structure: see text] The free energy of activation, deltaG*, for nitrogen inversion was calculated from the coalescence temperature for the methyl signals obtained via variable temperature NMR for a series of imino derivatives of the title compounds. There was a direct correlation between the long-range nonbonding circumannular orbital interactions between the heteroatoms in the 1,3-positions and the deltaG* for inversion of groups on nitrogen. Values of deltaG* range from 26 kcal/mol on systems with maximum interaction in the transition state (I and II) to 17 kcal/mole on those systems with minimal interaction (III and IV).
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