Abstract: | The 15N chemical shifts of aniline, the toluidines, xylidines, and several halogen and oxygen substituted anilines have been measured at the natural abundance level of 15N. Substituent parameters obtained by multiple regression analysis show that the methyl group induces comparable upfield shifts at the ortho and para positions (2·37 and 2·55 ppm/methyl, respectively) and a small (0·77 ppm/methyl) upfield shift at the meta position. The chemical shifts correlate reasonably well with 19F shifts of similarly substituted fluorobenzenes, with C-1 of the anilines themselves and with Hammett sigma values. While the shifts of C-methyl substituted anilines do not correlate with the methyl resonances of corresponding polymethylbenzenes, those of the halo- and alkoxyanilines show a reasonable parallelism with corresponding 13C-methyl shifts. The results are interpreted in terms of possible modes of transmission of electron density in an alternating and additive manner through the sigma framework. |