13C Nuclear Magnetic Resonance Spectroscopy. VI. Azines and Methyl Azines

Abstract

The 13C nuclear magnetic resonance spectra of the six known unsubstituted azines, pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, and s-tetrazine have been obtained, as well as those of some of their methyl derivatives. The carbon shieldings have been compared with those calculated theoretically, and estimates of the effects of π and σ electron densities and of bond orders are attempted. Reasonably good agreement between theory and experiment is obtained if the σ bonds between carbon and nitrogen are assumed to be very slightly polar.