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Substituent Conformational effects in vicinal 13 C 13 C spin–spin coupling constants
Author(s) -
Marshall James L.,
Faehl Larry G.,
Kattner Richard,
Hansen Poul Erik
Publication year - 1979
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.1270120309
Subject(s) - vicinal , coupling constant , chemistry , carbon 13 , spin (aerodynamics) , proton , crystallography , substituent , carbon fibers , proton spin crisis , coupling (piping) , stereochemistry , physics , materials science , organic chemistry , nuclear physics , thermodynamics , composite number , metallurgy , composite material , particle physics
A series of 7‐ 13 C‐labeled o ‐substituted toluene derivatives and carboxyl‐ 13 C‐isocrotonic and crotonic acid were synthesized and studied by 13 C NMR spectroscopy to obtain 13 C 13 C spin‐spin coupling constants involving the labeled carbon. The cis 3 J (CC) values were different from those in previous studies in that these J (CC) values were relatively small and the usual dependence of 3 J (CC) on the s ‐character of the terminal carbon was reversed. Further, a strong dependence of 3 J (CC) on the conformational orientation of a terminal carbonyl group was shown to exist. Through‐space interactions of the two coupling carbons were shown to contribute to these ‘anomalous’ results, and thus it was shown the cis carbon‐carbon couplings may not be directly related to geometrically equivalent proton‐proton couplings, as are other carbon‐carbon couplings.