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Deuterium isotope effects on 13C chemical shifts of intramolecularly hydrogen-bonded olefins

✍ Scribed by P. E. Hansen; S. Bolvig; F. Duus; M. V. Petrova; R. Kawecki; R. Krajewski; L. Kozerski

Publisher
John Wiley and Sons
Year
1995
Tongue
English
Weight
806 KB
Volume
33
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

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.

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