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Experimental and Theoretical Study of the Ethoxy Group Conformational Effect on 13 C Chemical Shifts in Ortho ‐Substituted Phenetols
Author(s) -
de Kowalewski Dora G.,
Kowalewski Valdemar J.,
Botek Edith,
Contreras Rubén H.,
Facelli Julio C.
Publication year - 1997
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199706)35:6<351::aid-omr6>3.0.co;2-t
Subject(s) - chemistry , chemical shift , conformational isomerism , anisole , polarizability , substituent , computational chemistry , basis set , alkoxy group , group (periodic table) , carbon 13 nmr , additive function , stereochemistry , molecule , organic chemistry , density functional theory , mathematical analysis , alkyl , mathematics , catalysis
The 13 C chemical shifts of nine 2‐X‐substituted phenetol derivatives were measured together with the 13 C chemical shifts of the corresponding X‐monosubstituted benzenes. Using an additivity scheme, the ethoxy cis ‐ and trans ‐ ortho ‐SCSs (substituent chemical shifts) at C‐6 and C‐2, respectively, were determined to be shielding effects 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 different phenetol conformers were obtained and the corresponding chemical shifts of all 13 C nuclei were calculated using the same basis set and the CHF‐GIAO approach. Results are discussed in terms of different interactions defining different conformations, particularly that between a polar bond and a proximate highly polarizable one. © John Wiley & Sons, Ltd.