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Deuterium‐induced primary and secondary isotope effects on 13 C,H coupling constants in halomethanes
Author(s) -
Sergeyeva N. D.,
Sergeyev N. M.,
Raynes W. T.
Publication year - 1998
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199804)36:4<255::aid-omr259>3.0.co;2-4
Subject(s) - chemistry , deuterium , kinetic isotope effect , coupling constant , halogen , proton , carbon 13 nmr , carbon 13 , deuterium nmr , spectral line , chemical shift , computational chemistry , analytical chemistry (journal) , stereochemistry , organic chemistry , atomic physics , nuclear physics , alkyl , physics , particle physics , astronomy
Primary p Δ J ( 13 C,H) and secondary s Δ J ( 13 C,H) isotope effects on carbon–proton coupling constants were measured in studies of proton‐ and deuteron‐coupled 13 C NMR spectra of the halomethanes CH n D m X 4‐ n ‐ m , where X is Cl, Br or I. Both effects are always negative. The magnitudes of p Δ J ( 13 C,H) increase with the number of halogen atoms whereas those of s Δ J ( 13 C,H) decrease. p Δ J ( 13 C,H) is almost linearly dependent on the number of halogen atoms whereas for s Δ J ( 13 C,H) the dependence is non‐linear. New results for the isotope effect on the 13 C,H coupling constant in fluoroform are in accord with data for the other members of the haloform series. For CH 3 Br and CH 3 I estimates of the main features of the surfaces for the 13 C,H coupling constants were made using known molecular force fields. © 1998 John Wiley & Sons, Ltd.