ISSN:
0749-1581
Schlagwort(e):
NMR
;
13C NMR
;
Conformation
;
Ab initio calculations
;
1-cis-Methoxy-1,3-trans-butadiene
;
1-trans-Methoxy-1,3-trans-butadiene
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
The proton-coupled 13C NMR spectra of 1-trans-methoxy- (2) and 1-cis-methoxy-1,3-trans-butadiene (3) are consistent with a methoxy heavy atom planar conformation with s-syn and s-anti orientations, respectively. Ab initio 6-31G* calculations confirmed such conformations. They were taken as model compounds to determine the influence of electrostatic interactions on the methoxy 13C NMR parameters. A shielding increase of 4 ppm is observed in 2, with respect to 3, for the OMe 13C chemical shift in an s-syn conformation and is ascribed to the attraction between the methyl and vinyl moieties as proposed by Li and Chesnut. The methyl 1J(C,H) coupling is not affected by this interaction, showing that the carbon 2p electrons are more polarizable than those in the 2s orbital.
Zusätzliches Material:
1 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/mrc.1260320402
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