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Proton n.m.r. spin‐tickling studies of 13 C‐labeled compounds. The correlation of J (C,H) and J (H,H)
Author(s) -
Marshall James L.,
Seiwell Ruth
Publication year - 1976
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.1270080806
Subject(s) - proton , coupling constant , chemistry , stereochemistry , spin (aerodynamics) , medicinal chemistry , crystallography , physics , thermodynamics , nuclear physics , particle physics
A tabulation has been compiled for twenty 13 CH coupling constants of various carboxylic acids and includes 2 J (C,H), 3 J (C,H) and 4 J (C,H) values of olefins (both cis and trans ); 3 J (C,H), 4 J (C,H) and 5 J (C,H) values of aromatics; 3 J (C,H) and 4 J (C,H) values of acetylenes; and 2 J (C,H) and 3 J (C,H) values of rigid aliphatics. This tabulation has been completed in the present study by the spin‐tickling proton n.m.r. study of 13 C‐ carboxyl ‐ endo ‐1,2,3,4,7,7‐hexachloronorbornene‐5‐carboxylic acid, which has established that the 2 J (C,H) value is negative and the 3 J (C,H) values (both cis and trans ) are positive in this system. A plot of these twenty J (C,H) values vs the corresponding J (H,H) values of geometrically equivalent model systems (where there is a proton in place of a carboxyl group) gives a correlation coefficient of 0·975 (with a slope of 0·62), indicating that carbon–proton and proton–proton couplings operate by similar mechanisms throughout this broad series of structural types.