Substituent effects on scalar J(13C, 13C) couplings in pyrimidines. An experimental and DFT study

Magnetic Resonance in Chemistry : MRC
Dora G de KowalewskiRubén H Contreras

Abstract

One- two- and three 13C, 13C (n = 1, 2, 3) scalar couplings, (n)J(C,C) in a set of pyrimidine derivatives were studied both experimentally at natural abundance and theoretically by their DFT calculation of all four contributions. Trends of non-contact terms are discussed and substituent effects are rationalized, comparing some of them with the corresponding values in benzene and pyridine. Although substituent effects on non-contact terms are relatively important, the whole trend is dominated by the Fermi contact term. According to the current literature, substituent effects on 1J(C,C) couplings in benzene derivatives are dominated by the inductive effect, which, apparently, is also the case in nitrogen heteroaromatic compounds. However, some differences observed in this work for substituent effects on 1J(C,C) couplings in pyrimidine derivatives suggest that in the latter type of compounds substituent effects can be affected by the orientation of the ring nitrogen lone pairs.

References

Sep 15, 1988·Physical Review A: General Physics·A D Becke
Nov 1, 2000·Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy·K Kamieńska-TrelaJ Wójcik
Jul 27, 2001·Journal of the American Chemical Society·A B ShtarevJ Michl
Aug 15, 2002·Journal of the American Chemical Society·Serdar KurtkayaJames P Snyder
Apr 8, 2004·Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry·Dieter CremerWolfgang Lüttke

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Citations

Sep 6, 2005·Magnetic Resonance in Chemistry : MRC·Rosa M ClaramuntJosé Elguero
Aug 19, 2009·The Journal of Physical Chemistry. a·Rubén H ContrerasCláudio F Tormena

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