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Molecular conformation of N , N ′‐diarylthioureas: An assessment by 1 H NMR and infrared spectroscopy
Author(s) -
Sudha L. V.,
Manogaran S.,
Sathyanarayana D. N.
Publication year - 1985
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260230802
Subject(s) - chemistry , intramolecular force , conformational isomerism , pyridine , chemical shift , substituent , hydrogen bond , molecule , nuclear magnetic resonance spectroscopy , infrared spectroscopy , crystallography , ring (chemistry) , proton nmr , spectroscopy , infrared , stereochemistry , computational chemistry , medicinal chemistry , organic chemistry , physics , quantum mechanics , optics
Several N , N ′‐dipyridyl‐ and N ‐phenyl‐ N ′‐pyridyl‐thioureas were examined in different solvents at various temperatures by 1 H NMR in order to study their conformational properties. The influence of concentration and the methyl substituent in the pyridine ring on the chemical shifts of the NH and pyridine groups was investigated. The observed chemical shifts are analysed in terms of the conformational properties of the molecules. Free energy barriers to the internal rotation about the CN bonds have been determined. Infrared spectra have been measured to supplement the NMR studies. Intramolecular hydrogen bonding played a major role in the preferred conformation of pyridylthioureas. The data further revealed an interesting dynamic exchange phenomenon occurring in symmetric N , N ′‐dipyridylthioureas between two intramolecularly hydrogen bonded conformers.