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Deuterium isotope effects on 13 C chemical shifts of intramolecularly hydrogen‐bonded olefins
Author(s) -
Hansen P. E.,
Bolvig S.,
Duus F.,
Petrova M. V.,
Kawecki R.,
Krajewski R.,
Kozerski L.
Publication year - 1995
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.1260330803
Subject(s) - chemistry , kinetic isotope effect , deuterium , tautomer , steric effects , hydrogen , chemical shift , hydrogen bond , computational chemistry , substituent , photochemistry , deuterium nmr , medicinal chemistry , organic chemistry , molecule , nuclear magnetic resonance spectroscopy , physics , quantum mechanics
A series of intramolecularly hydrogen‐bonded enamines, enols and enethiols with ester carbonylic, ketonic carbonylic, thioester carbonylic, nitro and sulphoxide acceptors were investigated to obtain 13 C chemical shifts and deuterium isotope effects. Results from 33 new compounds and six remeasurements are compared with already existing data. An important aim was to show that isotope effects on chemical shifts are useful descriptors of hydrogen‐bonded systems and not only a parameter proportional to the 13 C chemical shifts. Substituent effects were studied and the donors and acceptors ranked according to their abilities to support hydrogen bonding. Steric effects strengthen the hydrogen bonding in cyclic five‐membered β‐diketones. Plots of two‐bond [ 2 ΔC(OD)] vs. four‐bond isotope effects [ 4 ΔC(OD)] show that 4 ΔC(OD) increases with increasing hydrogen bond strength and that large deviations from this relationship can be an indicator of tautomerism.