CARBON-13 NUCLEAR MAGNETIC RESONANCE STUDIES OF 3-SUBSTITUTED PYRIDINES

Carbon-13 magnetic shieldings for eight 3-substituted pyridines are reported and compared with those of the corresponding monosubstituted benzenes. Thirty of the forty carbon shieldings measured in the spectra of the pyridines yield substituent effects that are within ±1.3 ppm of those found for the benzenes. Shieldings of the carbons in the 6 position in the pyridines are shown to reflect electron release or withdrawal by substituent groups.