Modelling 13C substituent chemical shifts in 3-aryl-2-cyanoacrylamides. An application of the dual-substituent parameter non-linear resonance (DSP-NLR) method

Abstract

¹³ C Substituent chemical shifts (SCS) in 3-phenyl- and 3-thienyl-2-cyanoacrylamides have been examined by multiple linear regression analysis using standard field parameters (σ_F) together with various resonance parameters. The side-chain SCS are best modelled by a method, DSP-NLR, which explicitly allows for a non-linear resonance response. A combination of polarization and resonance mechanisms accounts satisfactorily for substituent effects at all side-chain sites.