Nuclear Quadrupole Resonance in Solid Diazines

Abstract

Nitrogen−14 nuclear quadrupole resonance data are reported for pyridazine, pyrazine, and pyrimidine. The spectra are analyzed assuming sp2 hybridization of the nitrogen σ bonding and lone-pair orbitals. Coupling constants and asymmetry parameters are interpreted in terms of electron densities in σ and π orbitals and compared with values for pyridine. Evidence is presented indicating significant polarization of the σ bonds and strong localization of the lone-pair electrons. Good agreement is found with LCAO MO calculations of π-charge densities.