Effects of electronic resonance interaction on the methoxy group NMR parameters. Theoretical and experimental study of substituted 2-methoxypyridines
In order to increase the understanding of the interactions which define the planar conformation of the methoxy group with respect to the aryl ring in methyl aryl ethers and the effect these interactions have on the methoxy NMR parameters, 17O and 13C spectra were measured and ab initio optimized geo...
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| Autores principales: | , , , , |
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| Formato: | Artículo publishedVersion |
| Publicado: |
1993
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| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_00223654_v97_n1_p91_Contreras https://repositoriouba.sisbi.uba.ar/gsdl/cgi-bin/library.cgi?a=d&c=artiaex&d=paper_00223654_v97_n1_p91_Contreras_oai |
| Aporte de: |
| Sumario: | In order to increase the understanding of the interactions which define the planar conformation of the methoxy group with respect to the aryl ring in methyl aryl ethers and the effect these interactions have on the methoxy NMR parameters, 17O and 13C spectra were measured and ab initio optimized geometries were calculated for three different conformations of the methoxy group in 2-methoxy-5-X-pyridines (X = H, NO2, and NH2). 17O and 13C chemical shifts were also calculated using the LORG approach. It was found that, contrary to what has been commonly assumed, the oxygen and the carbon of the methoxy group are deshielded when the electronic resonance interaction is increased. Therefore, the large 13C deshielding effect observed for a conformation with an out-of-plane methoxy group in aryl methyl ethers and related compounds has to be attributed to the inhibition of the attractive van der Waals forces between the methyl moiety and the aromatic ortho-cis carbon atom. © 1993 American Chemical Society. |
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