substituent effects in the 13c-nmr spectra of six-membered nitrogen heteroaromatic compounds取代基效应的色谱仪光谱六元氮heteroaromatic化合物.pdf

Int. J. Mol. Sci. 2005, 6, 11-17 International Journal of Molecular Sciences ISSN 1422-0067 © 2005 by MDPI /ijms/ Substituent Effects in the 13C-NMR Spectra of Six-Membered Nitrogen Heteroaromatic Compounds Janusz Oszczapowicz Department of Chemistry, Warsaw University, Pasteura 1, 02-093 Warszawa, Poland; Fax: (+48) 22- 822-5996; e-mail oszczapo@.pl Received: 15 June 2004; in revised form: 25 January 2005 / Accepted 26 January 2005 / Published: 31 January 2005 ________________________________________________________________________________ 13 Abstract: It is shown that the C-NMR chemical shifts of carbon atoms in substituted six- membered heteroaromatic compounds correlate with the correponding additivity parameters for substituted benzene derivatives. Thus, for precalculation of chemical shifts in such compounds, just one set of parameters can be used. The differences between experimental chemical shifts and those calculated from correlation with the common set may provide insights into intramolecular interactions not reported in the literature. Keywords: 13C-NMR, substituent polar effects, pyridines, pyrazines, pyrimidines ________________________________________________________________________________ Introduction Substitution of any six-membered aromatic or heteroaromatic ring by a certain substituent causes changes of