Deuterium Isotope Effects on Aromatic Carbon-13 Chemical Shifts. III. One-, Two-, and Three-Bond Isotope Effects on the 13C Chemical Shifts of 3-Substituted Pyridines

The one-, two-, and three-bond deuterium isotope effects (1Δ, 2Δ, and 3Δ) on the 13C chemical shifts of 3-substituted pyridines are reported. 1Δ, 2Δ, and 3Δ are correlated with the 13C chemical shifts of the observed carbons. 1Δ, show a linear correlation with the 13C chemical shifts with a positive slope. On the other hand, 2Δ and 3Δ show linear correlations with the negative slopes. They can thus be interpreted in terms of the π-electron density change by the substituent and the electron release effects by carbons one and two bonds apart from deuterium, respectively.