N-(substituted phenyl)-2-chloroacetamides: LSER and LFER study

Abstract

The UV absorption spectra of twelve N-(substituted phenyl)-2-chloroacetamides were recorded in eighteen solvents. The effect of specific and non-specific solvent–solute interactions on the absorption maxima shifts was evaluated by using the Kamlet–Taft solvent parameter set, i.e. applying linear solvation energy relationships (LSER) principles. Optimized geometries and experimental results were interpreted by using DFT (B3LYP/6-311+G(d,p) method) and time-dependent density functional (TD-DFT) method. Overall electron density in both ground and excited state was obtained by the use of Quantum Theory of Atoms in Molecules, i.e. Bader’s analysis. It was found that both solvent and substituents cause appropriate change of the extent of conjugation in the molecules that further affect their intra-molecular charge transfer (ICT) character. Linear free energy relationships (LFERs) were applied to the substituent-induced NMR chemical shifts (SCS) using single substituent parameter (SSP) and dual substituent parameter (DSP) model. Transmission mode of the electronic effects of substituent was discussed according to the results of theoretical calculations and results of LFER correlations. Comparative analysis of presented results with the ones published for structurally similar series of amide which contained cyano group, instead chlorine, provides additional information on the impact of present group to the properties of investigated compound. Keywords: N-(substituted phenyl)-2-chloroacetamides, UV absorption spectra, Solvent effects, Substituent effects, Molecular geometry optimization, Bader’ analysis