13C chemical shifts of symmetrically substituted biphenyls: Unambiguous signal assignment for the carbons ortho and para to an aryl group

✍ Scribed by Karou Fuji; Toshihide Yamada; Eiichi Fujita

• Book ID: 102950893
• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 556 KB
• Volume: 17
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270170406

✦ Synopsis

Abstract

The natural abundance ^13^C NMR spectra of 2,2′‐dimethyl‐, 2,2′‐dimethoxy‐ and 2,2′‐dihydroxybiphenyls, and a series of 2,2′‐dimethoxy‐5,5′‐disubstituted biphenyls were recorded. Unambiguous signal assignments of the carbons ortho and para to an aryl ring in biphenyls were made by selective deuteration and/or the graphical method for ^1^H single frequency off‐resonance decoupled spectra. Contrary to the reported assignments, it was shown that the signal for C‐6 in 2,2′‐dimethylbiphenyl clearly appears at lower field than that for C‐4. The signals for the ortho carbons (C‐6) of 2,2′‐dimethoxy‐5,5′‐disubstituted biphenyls generally appeared at lower fields than those for the para carbons (C‐4). The validity of applying deuterium isotope shifts to the assignments of ^13^C chemical shifts of di‐ and tetra‐substituted biphenyls is also discussed.