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13 C chemical shifts of symmetrically substituted biphenyls: Unambiguous signal assignment for the carbons ortho and para to an aryl group
Author(s) -
Fuji Karou,
Yamada Toshihide,
Fujita Eiichi
Publication year - 1981
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270170406
Subject(s) - deuterium , aryl , chemical shift , chemistry , spectral line , ring (chemistry) , medicinal chemistry , isotope , group (periodic table) , signal (programming language) , stereochemistry , organic chemistry , physics , atomic physics , alkyl , quantum mechanics , astronomy , computer science , programming language
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.