
%0 Journal Article
%A Bate, DL 
%A Rae, ID 
%T Aromatic amides. VIII. Z,E Isomer ratios and stereochemistry about aryl-nitrogen bonds in N-aryl amides and thioamides
%J Australian Journal of Chemistry
%D 1974/12/01
%V 27
%N 12
%P 2611-2616
%K 
%R https://doi.org/10.1071/CH9742611
%U https://www.publish.csiro.au/paper/CH9742611 
%X For 4?-substituted 2?,6?-diethylacetanilides, the Z/E isomer ratio depends on the nature of the 4?- substituent, the Z isomer being relatively favoured by electron-withdrawing substituents. The acyla- tion shifts of the ortho aromatic protons for 4?-substituted thiopivalanilides are greatest when the substituent is electron- withdrawing. These relationships complement the previously observed changes in isomer ratios of thioamides and acylation shifts of amides. It is proposed that the Z isomer is more nearly planar when the 4?- substituent is electron-withdrawing. As the substituent becomes more electron-releasing, the amide group is able to twist more out of the ring plane and the Z isomer is destabilized, relative to the E isomer, by n-&#960; electron repulsions. 
