The 13C NMR spectra of a number of ring-substituted 9-vinylcarbazoles and cis- and trans-9-propenylcarbazoles were studied. It was found that the CB chemical shifts of the vinyl atoms of these compounds correlate satisfactorily with the σ constants of the substituents in the 3 and 6 position of the carbazolyl rings; the slopes of the straight lines increase in the order 5.84, 7.68, 9.56. The inductive and conjugation components of the effect of the substituents on the chemical shifts of the CB atoms were evaluated. It follows from the results obtained that the effects of p-π conjugation are realized not only in the relatively planar isomers but also in the nonplanar cis isomers of 9-alkenylcarbazoles.
ASJC Scopus subject areas
- Organic Chemistry