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Axial/equatorial populations in α‐hetero‐substituted cyclohexanone Oximes and O ‐methyl oximes
Author(s) -
Ribeiro Douglas S.,
Olivato Paulo R.,
Rittner Roberto
Publication year - 2000
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 - 10.1002/1097-458x(200008)38:8<627::aid-mrc680>3.0.co;2-m
Subject(s) - chemistry , cyclohexanone , cyclohexanone oxime , organic chemistry , stereochemistry , medicinal chemistry , computational chemistry , catalysis
Axial equatorial populations were determined for ( E )‐2‐X‐cyclohexanone oximes and O ‐methyl oxime ethers in chloroform by the Eliel method [X = F, Cl, Br, OCH 3 , N(CH 3 ) 2 , SCH 3 ]. A novel approach is presented, which uses 1 H NMR data from the protons bonded to C‐6. The conformational proportions were also obtained from the C‐4 chemical shifts, the Z ‐isomer spectral parameters being taken as reference for calculation. For both series, all substituents adopt preferentially the axial conformation (86– 96%), but the O ‐methyl oxime ethers present an enhanced axial population compared with the corresponding oximes, owing to the accepted occurrence of a π C = NOH /σ * CX stabilizing interaction. Copyright © 2000 John Wiley & Sons, Ltd.