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ABSTRACT Linear free energy relationships (LFER) were applied to the kinetic data for the reaction of 5-substituted orotic acids, series 1, with diazodiphenylmethane (DDM) in N, N-dimethylformamide and compared with results obtained for 2-substituted benzoic acids, series 2. The correlation analysis of the kinetic data with σ substituent parameters was carried out using SSP (single substituent parameter) methods. From the sign and value of proportinality constant ρ, lower sensitivity to the substituent effect was obtained in series 1, 0.876, than in the series 2, 1.877. Evaluation of substituent 'ortho-effect' was performed using the Charton model, which includes the steric substituent parameter, and Fujita and Nishioka's model, which describes the total ortho -effect as contribution of ordinary polar effect, the ortho -steric and ortho -polar effects. Results of correlations, obtained by using the Charton model, showed highest contribution of the polar effect, 0.861 vs. 2.101, whereas the steric effect is of lowest significance, 0.117 vs. 0.055, for series 1 and 2, respectively. Also, a low negative value of coefficient with the steric effect, -0.08, obtained from the Fujita-Nishioka model indicated low steric effect, influencing a decrease of the reaction rate in series 1. The structural and substituent effects were also studied by using the density functional theory method, and together with kinetic data, it gave a better insight into the influence of the effect of both geometry and substituent on the π−electron density shift induced reactivity of investigated acids. [ABSTRACT FROM AUTHOR]

The derivatives of isatin have already been known to display a variety of biological activities. Therefore, the studies on their activity and its relation to structure have recently become a popular subject for investigation. The examined compounds were synthesized by the reaction of isatin and substituted primary amines and characterized by spectroscopic methods. The investigation of the antimicrobial and antioxidative activity of the synthesized compounds was performed by broth microdilution method. As for the characterization of the investigated isatin based Schiff bases, the linear solvation energy relationships (LSER) were used to analyze the solvent influence on the UV absorption maxima shifts (νmax), using the well known Kamlet-Taft model and taking geometrical isomers into consideration when possible. Linear free energy relationships (LFER) were used to analyze substituent effect on pKa, as well as NMR chemical shifts and νmax values. The antimicrobial activity and characterization were related using both experimental and theoretical methods. [ABSTRACT FROM AUTHOR]

The derivatives of isatin (1H-indole-2,3-dione) have already been reported to show a variety of biological activities. However, there have hitherto been no reports on the solvatochromic effects of isatin derivatives, and it could be of interest to study and relate them to their electronic structures, as a part of the characterisation of these compounds. Linear solvation energy relationships (LSER) were used to analyze the influence of the solvent on the shifts of the UV absorption maxima of investigated isatin derivatives, i.e., isatin based Schiff bases, using Kamlet-Taft model. Linear free energy relationships (LFER) were applied to the substituent-induced NMR chemical shifts (SCS) using a single substituent parameter (SSP). The obtained correlations together with theoretical calculations gave insight into the influence of the molecular conformation on the transmission of substituent effects, as well as on solute-solvent interactions. The molecular electrostatic potential (MEP) surface map was plotted over the optimized geometry of the molecules in order to visualize the electron density distribution and explain the origin of the solvent- -solute interactions. [ABSTRACT FROM AUTHOR]