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Experimental and Theoretical Study of the Ethoxy Group Conformational Effect on 13C Chemical Shifts in Ortho-Substituted Phenetols

✍ Scribed by Dora G. de Kowalewski; Valdemar J. Kowalewski; Edith Botek; Rubén H. Contreras; Julio C. Facelli

Publisher
John Wiley and Sons
Year
1997
Tongue
English
Weight
239 KB
Volume
35
Category
Article
ISSN
0749-1581

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✦ Synopsis

The 13C chemical shifts of nine 2-X-substituted phenetol derivatives were measured together with the 13C chemical shifts of the corresponding X-monosubstituted benzenes. Using an additivity scheme, the ethoxy cisand transortho-SCSs (substituent chemical shifts) at C-6 and C-2, respectively, were determined to be shielding e †ects of 16.5 and 10.9 ppm, respectively, which are close to those determined previously in anisole derivatives. Optimized geometries at the Hartree-Fock level employing a D95** basis set for three di †erent phenetol conformers were obtained and the corresponding chemical shifts of all 13C nuclei were calculated using the same basis set and the CHF-GIAO approach. Results are discussed in terms of di †erent interactions deÐning di †erent conformations, particularly that between a polar bond and a proximate highly polarizable one.

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