The relative sign of the proton-proton couplings in diazine N-oxide

Abstract

Although the n.m.r. spectrum of pyridine was originally analysedl-3 on the basis of a positive value for the coupling across the nitrogen ( J 2 , 6 +OS40 HZ), a recent analysis4 of the spectrum obtained with simultaneous double-irradiation of the 14N nucleus has established that the coupling is negative ( J 2 , 6 -0.13 HZ). Negative values for J 2 , 6 have also been derived5 for 3-acetylpyridine (-0.21 Hz) and other /3-monosubstituted pyridines.