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1 H NMR studies of intramolecular hydrogen bonding in N ‐(pyridyl)amides of 6‐methylpicolinic acid N ‐oxide
Author(s) -
Brzezinski Bogumil
Publication year - 1979
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270120709
Subject(s) - intramolecular force , chemistry , chemical shift , substituent , pyridine , hydrogen bond , chloroform , ring (chemistry) , proton , proton nmr , pyridine n oxide , amide , oxide , medicinal chemistry , crystallography , stereochemistry , molecule , organic chemistry , physics , quantum mechanics
The 1 H NMR spectra of seven N ‐(pyridyl)amides of 6‐methylpicolinic acid N ‐oxide in chloroform were obtained. The influence on the chemical shifts of the NH protons of temperature, concentration and the CH 3 substituent in the pyridine ring was studied. The NH protons were found to be shifted to low fields (∼14 ppm) owing to the formation of strong intramolecular hydrogen bonding. The influence of the pyridine ring on the chemical shift of the NH proton is comparable with the inductive effect of the p ‐nitrophenyl group. The hindered rotation around the N ‐pyridyl bond of N ‐(α‐pyridyl)amides of 6‐methylpicolinic acid in solution is discussed.