Linear free energy relationships (LFER) were applied to the IR, 1H and 13C
NMR spectral data of N-(substituted phenyl)-2-cyanoacetamides. A variety of
substituents were employed for phenyl substitution and fairly good
correlations were obtained using the simple Hammett and the Hammett-Taft
dual substituent parameter equations. The correlation results of the
substituent induced 13C NMR chemical shifts (SCS) of the C1, C=O and N-H
atom indicated different sensitivity with respect to electronic substituent
effects. A better correlation of the SCSC=O with a combination of
electrophilic and nucleophilic substituent constants indicated a significant
contribution of extended resonance interaction (?-delocalization) within the
?1-unit. The conformations of the investigated compounds were studied using
the DFT B3LYP/6-311G method and, together with the results of 13C NMR and
IR spectroscopic studies, a better insight into the influence of such a
structure on the transmission of electronic substituent effects was
obtained.
Substituent effect on IR, 1H and 13C NMR spectral data in n-(substituted phenyl)-2-cyanoacetamides: A correlation study