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Pronounced stereospecificity of 1 H, 13 C, 15 N and 77 Se shielding constants in the selenophenyl oximes as shown by NMR spectroscopy and GIAO calculations
Author(s) -
Afonin Andrei V.,
Pavlov Dmitry V.,
Ushakov Igor A.,
Schmidt Elena Yu.,
Mikhaleva Al'bina I.
Publication year - 2009
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.2471
Subject(s) - chemistry , chemical shift , stereospecificity , ring (chemistry) , nmr spectra database , resonance (particle physics) , nuclear magnetic resonance spectroscopy , crystallography , spectral line , stereochemistry , analytical chemistry (journal) , organic chemistry , atomic physics , physics , astronomy , catalysis
In the 1 H and 13 C NMR spectra of 1‐(2‐selenophenyl)‐1‐alkanone oximes, the 1 H, the 13 C‐3 and 13 C‐5 signals of the selenophene ring are shifted by 0.1–0.4, 2.5–3.0 and 5.5–6.0 ppm, respectively, to higher frequencies, whereas those of the 13 C‐1, 13 C‐2 and 13 C‐4 carbons are shifted by 4–5, ∼11 and ∼1.7 ppm to lower frequencies on going from the E to Z isomer. The 15 N chemical shift of the oximic nitrogen is larger by 13–16 ppm in the E isomer relative to the Z isomer. An extraordinarily large difference (above 90 ppm) between the 77 Se resonance positions is revealed in the studied oxime isomers, the 77 Se peak being shifted to higher frequencies in the Z isomer. The trends in the changes of the measured chemical shifts are well reproduced by the GIAO calculations of the 1 H, 13 C, 15 N and 77 Se shielding constants in the energy‐favorable conformation with the syn orientation of theCNOH group relative to the selenophene ring. Copyright © 2009 John Wiley & Sons, Ltd.