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13C NMR Spectra of some Simetrically 2, 2’ -Disubstituted Stlbenes: Conjugational and Conformational Effects13C NMR Spectra of some Simetrically 2, 2’ -Disubstituted Stlbenes: Conjugational and Conformational Effects

In the 13C NMR spectra of symmetrically 2, 2’ -disubstituted cis-stilbenes the decrease of alpha-effects and increase of gamma-effects at ortho-carbons with respect to trans-isomers were observed. However, the most significant differences in substituent effects between trans- and cis-isomers were founf for gamma-effects, at unsubstituted ortho-C-6 and C-4 atoms. The one bond C-H splitting of olefinic carbons is greater in cis-than trans-stilbenes. The differences in substituent effects and apparent coupling constants are asumed to originate mainly from the different conjugational interactions in cis- and trans-stilbenes. The conformational and configurational differences of these molecules were substantiated by molecular mechanics calculations.

2 ; 2’ -disubstituted cis-stilbenes ; 13C NMR Spectra ; Conjugational and Conformational Analysis

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