Inter- and intra-molecular hydrogen bonding effects on geminal 15N, 1H spin coupling and 15N chemical shifts in pyridine derivatives

The two‐bond 15N,H coupling constant in 3,5‐dimethylpyridine was determined in 30 solvents and shown to vary between −11 and −3 Hz. An increasing ability of the solvent to form hydrogen bonds causes a steady decrease in ∣ 2J(15N,H)∣, which is also observed with some selected pyridine derivatives with intramolecular hydrogen bonds. A linear correlation is found between the positive lone‐pair effect on ∣2J(15N,H)∣ and the decrease in nitrogen shielding.