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37 Cl/ 35 Cl isotope effects in 13 C NMR spectroscopy of chlorohydrocarbons
Author(s) -
Aliev Abil E.,
Harris Kenneth D. M.
Publication year - 1993
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/mrc.1260310111
Subject(s) - chemistry , isotope , isotopic shift , kinetic isotope effect , carbon 13 , nuclear magnetic resonance spectroscopy , chemical shift , isotopes of chlorine , analytical chemistry (journal) , spectral line , nmr spectra database , chlorine , spectroscopy , stable isotope ratio , nuclear magnetic resonance , deuterium , atomic physics , stereochemistry , physics , quantum mechanics , organic chemistry , astronomy , chromatography
Isotope effects on the chemical shift of 13 C directly bonded to the isotopes 35 Cl and 37 Cl are reported for a wide range of chlorohydrocarbons. By recording 13 C NMR spectra under conditions of composite pulse 1 H decoupling, 13 C resonances can be obtained that are sufficiently narrow to allow the very small splittings of the order of a few ppb due to the 35 Cl/ 37 Cl isotope effect to be resolved at ambient temperature. Observation of this phenomenon allows the routine identification of 13 C resonances due to carbon atoms directly bonded to chlorine, since, for natural abundance samples, the isotope effect splits the 13 C signal into a set of lines with a characteristic intensity distribution. Various structural features influencing the magnitude of the isotope effect have been elucidated, and the temperature dependence of the isotope effect is also discussed. From low‐temperature 13 C NMR spectra for chlorocyclohexane, isotope shifts for the carbon atom directly bonded to chlorine were measured separately for the axial and equatorial conformations. The measured values indicate that the isotope shift is larger for the axial conformation.