Additivity of 13C-1H and 1H-1H spin-spin coupling constants in six-membered aromatic nitrogen-containing heterocycles

Abstract

We have analyzed proton-coupled 13C NMR and PMR spectra of pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, and 1,2,4-triazine for one-molar solutions of the compounds in DMSO-D6. Comparison of the values obtained for the 13C-1H and 1H-1H spin-spin coupling constants with the values calculated on the basis of the spin-spin coupling constants in pyridine and benzene has shown that it is possible to predict the constants using linear additive equations. Substantial nonlinear deviations (5–6 Hz) are observed for 1JCH when the carbon atom is located between two adjacent nitrogen atoms.