Substituent Effect on Ir , 1 H - and 13 C - Nmr Spectral Data in N - ( Substi - Tuted Phenyl ) - 2 - Cyanoacetamides : a Correlation Study

Linear free energy relationships (LFER) were applied to the IR, Hand C-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 C-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 (π–delocalization) within the π1–unit. The conformations of the investigated compounds were studied using the DFT B3LYP/6-311G** method and, together with the results of C-NMR and IR spectroscopic studies, a better insight into the influence of such a structure on the transmission of electronic substituent effects was obtained.