The nitrogen atom orbital populations in the azabenzenes as determined by their¹⁴N nuclear quadrupole coupling constants

Abstract

An analysis is presented of the 14N nuclear quadrupole coupling constants of pyridine, γ-picoline, pyrazine, tetramethylpyrazine, phenazine and s-triazine in terms of the populations of the sigma and pi bonding orbitals around the nitrogen atom. The limitations inherent in the interpretation of the quadrupole coupling data are discussed and it is shown that it is best used to determine the difference between the sigma and pi orbital populations. By assuming that the sigma orbital population remains constant for all these compounds values of the pi orbital populations are obtained and compared with the predictions of molecular orbital theories of various degrees of sophistication.