Evidence of N-N single bond as a hindrance of electron delocalization in cyclic and acyclic azines

摘要

In the grouping C=N-N=C both in heterocyclic and acyclic azines the N-N bond has a character of an isolated single bond, the C=N bonds that of a double bond. This has been confirmed in solutions by comparison of reduction potentials of model compounds and by evaluation of substituent effect using a Linear Free Energy Relationship, in solid state by x-ray data. As a consequence, in cyclic (pyridazines and 1,2,4-triazines) as well as acyclic compounds, bearing the grouping C=N-N=C, the electron delocalization over the central N-N bond is very limited or absent.