13C and15N NMR study of substituted 1,2,4-triazines

1995

13C and 15N NMR spectra of eight substituted 1,2,4-triazines were measured and assigned. The assignments of the 13C NMR spectra were based on the substituent chemical shifts and nJ(C,H) coupling constants. 15N NMR chemical shifts generally showing well separated ranges were assigned by the proton coupled 15N NMR spectra. 15N NMR chemical shifts of N-4 in 3- and 5-methoxy or -thiomethyl-substituted 1,2,4-triazines were found to be related significantly (confidence level >99%) with the π-charge at N-4 calculated by a semi-empirical molecular orbital (AM1) procedure. For the 15N NMR chemical shifts of N-1 and N-2, no reliable correlations with the molecular electronic properties such as AM1 π-…