Premium
Spectroscopic studies on olefins—III: NMR of cis ‐ and trans ‐ disubstituted olefins
Author(s) -
Rummens F. H. A.,
de Haan J. W.
Publication year - 1970
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.1270020406
Subject(s) - allylic rearrangement , vicinal , steric effects , chemistry , proton , carbon 13 nmr , proton nmr , coupling constant , spectral line , nmr spectra database , stereochemistry , computational chemistry , crystallography , medicinal chemistry , organic chemistry , physics , nuclear physics , catalysis , particle physics , astronomy
The proton NMR spectra of four cis / trans pairs of 1,2‐disubstituted olefins have been analysed. The observed trends of the olefinic, vicinal and allylic proton‐proton coupling constants are discussed in terms of rehybridization at the sp 2 carbon atoms. It is found that in these substances the trans ‐allylic couplings are generally more negative than the cis ‐allylic couplings contrary to Barfield's 1 theoretical prediction but in agreement with some earlier experimental data. Steric hindrance between cisoid substituents is cited as the probable origin of this end related trends.