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Six α,β,β-trifluorostyrenes with the following substituents,viz.,p-MeO,p-Me,m-Me,p-Cl,m-Cl,and rn-CF_3,were synthesized by the reaction of the corresponding Grignard reagentswith tetrafluoroethylene in tetrahydrofuran.Similarly,a-and β-trifluoroethenylnaphthalenes wereprepared.(?)The substituent electronic effects on the ~(19)F-NMR parameters were investigated for the trifluoro-styrenes(I).Linear correlations between the Hammett σ constants and the following ~(19)F-NMR para-meters were established,namely,chemical shifts δ(F~1)and δ(F~2),coupling constants J_(12),differencesof chemical shifts ⊿δ_(—1)(δ(F~3)—δ(F~1))or ⊿δ_(3—2).The results are consistent with previous expectationsbased on the simple concept of“distorted π-electron clouds”.Facts are presented which indicatethat the ⊿δ_(3—1)(or ⊿δ_(3—2)values may serve as empirical measures of the degree of polarization ofthe π bonds of these fluoroolefins.
Six α, β, β-trifluorostyrenes with the following substituents, viz., P-MeO, p-Me, m-Me, p-Cl, m-Cl, and rn-CF_3, were synthesized by the reaction of the corresponding Grignard (?) The substituent electronic effects on the ~ (19) F-NMR parameters were investigated for the trifluoro-styrenes (I). Linear correlations between the Hammett σ constants The chemical shifts δ (F~1) and δ (F~2), coupling constants J_ (12), differencesof chemical shifts ⊿δ_ (-1) The results are consistent with previous expectations based on the simple concept of “distorted π-electron clouds.” Facts are presented which indicate that the same ⊿δ_ (3-1) (or ⊿δ_ (3-2) values may serve as empirical measures of the degree of polarization of the π bonds of these fluoroolefins.