Premium
Stereodynamics of some pyridoxine derivatives
Author(s) -
Rakhmatullin I. Z.,
Galiullina L. F.,
Balandina A. A.,
Garipov M. R.,
Strelnik A. D.,
Galiullina A. S.,
Shtyrlin Y. G.,
Klochkov V. V.
Publication year - 2017
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.4528
Subject(s) - chemistry , substituent , ring (chemistry) , nuclear magnetic resonance spectroscopy , crystallography , activation energy , stereochemistry , twist , conformational isomerism , proton nmr , acetal , computational chemistry , molecule , organic chemistry , geometry , mathematics
The conformational properties of three pyridoxine derivatives were studied by 1 H dynamic NMR spectroscopy. Conformational exchange caused by a rotation of 2‐nytrophenyl group around one single C–C bond, of 2,4‐dinitrophenyl substituent around two single C–O bonds, and twist‐twist transformations of the seven‐membered ketal cycle was observed by NMR experiments at low temperatures. Meanwhile, the conformational exchange of the acetal ring remains fast in the NMR timescale even at 198 K. The energy barriers for all observed conformational exchange processes were determined by the lineshape analysis of dynamic NMR spectra. The activation barriers of the 2‐nitrophenyl group rotation were almost the same for all studied compounds, about 40–41 kJ/mol. The energy barriers of the conformational exchange processes of the 2,4‐nitrophenyl group and the ketal cycle increased significantly up to 10 kJ/mol in comparison with previously studied compounds with similar structure. Copyright © 2016 John Wiley & Sons, Ltd.