Nitrogen-15 magnetic resonance spectroscopy XVI—natural-abundance spectra of aromatic amines

✍ Scribed by Robert L. Lichter; John D. Roberts

• Publisher: John Wiley and Sons
• Year: 1974
• Tongue: English
• Weight: 379 KB
• Volume: 6
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270061206

✦ Synopsis

Abstract

The ^15^N chemical shifts of aniline, the toluidines, xylidines, and several halogen and oxygen substituted anilines have been measured at the natural abundance level of ^15^N. 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 ^19^F 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 ^13^C‐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.