Studies on 13C magnetic resonance spectroscopy. XIII. 13C and 1H NMR of 4-substituted pyridazine and 2-substituted pyrazine derivatives.

^<13>C chemical shifts of 4-substituted pyridazines and 2-substituted pyrazines, together with 1H chemical shifts of the former compounds were measured. Linear correlations of the 13C and 1H chemical shifts of 4-substituted pyridazines with those of monosubstituted benzenes and monosubstituted pyridines and with substituent constants σπ were found. In addition, similar trends were noted for 2-substituted pyrazines. Chemical shifts of pyridazines and pyrazines can be predicted on the basis of these relationships.