
%0 Journal Article
%A Yamagami, C 
%A Takao, N 
%A Takeuchi, Y 
%T <sup>15</sup>N Nuclear Magnetic-Resonance Spectra of <I>ortho</I>-Substituted Phenylacetanilides: The Origin of &#947;-<I>syn</I> Effects
%J Australian Journal of Chemistry
%D 1989/04/01
%V 42
%N 4
%P 463-469
%K 
%R https://doi.org/10.1071/CH9890463
%U https://www.publish.csiro.au/paper/CH9890463 
%X The 15N chemical shifts of X &#945; and Y &#945;, i.e., the nuclei through which the side chains, X and Y, respectively, of o-substituted phenylacetanilides (2a) are bonded to the aromatic ring were determined. There was observed a uniform upfield shift (&#947;syn effect). In order to explore the origin of the &#947; effect, other o-disubstitutes benzenes (2b-d) were also examined. The values of D, defined as the difference between &#947; &#945; substituent chemical shifts of the ortho (2) and para (3) series of compounds, and considered as a measure of the &#947;-syn effect, were correlated with various electronic and steric substituent parameters. Correlations with electronegativity and van der Waals terms were successful. Examination of the correlations indicated that the &#947;-syn effect is mostly governed by electronegativity. The classic steric compression theory does not seem very convincing as a means of explaining the shielding &#947;-syn effect observed in the present study. 
