Natural abundance proton‐coupled 15 N NMR spectra of pyridines observed from proton polarization transfer experiments

Natural abundance proton‐coupled 15 N NMR spectra have been observed for pyridine and a series of mono‐ and disubstituted pyridines using polarization transfer achieved by the selective population transfer method. The magnitudes and signs of the 15 N 1 H spin‐spin coupling constants between the ring‐nitrogen and ring‐protons are determined from complete iterative spectral analysis and/or selective population transfer experiments. Substituent effects on the 15 N 1 H coupling constants are discussed and compared with those for 13 C 1 H couplings in substituted benzenes.