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An efficient computational approach for the evaluation of substituent constants
Boris Galabov1, Sonia Ilieva, Henry F Schaefer
1Department of Chemistry, University of Sofia, Sofia 1164, Bulgaria.
The Journal of Organic Chemistry
|August 12, 2006
Summary
This study introduces a computational method to predict substituent constants for benzene derivatives. Electrostatic potential values accurately correlate with reactivity, with water solvent enhancing substituent effects.
Area of Science:
- Computational chemistry
- Physical organic chemistry
Background:
- Understanding substituent effects is crucial in organic chemistry.
- Accurate prediction of electronic structure parameters is essential for reactivity studies.
Purpose of the Study:
- To develop an efficient computational approach for evaluating sigma(0) substituent constants.
- To investigate the relationship between electronic structure and experimental reactivity constants.
- To assess the influence of solvent effects on substituent properties.
Main Methods:
- Density functional theory (DFT) computations at B3LYP/6-311+G(2d,2p) and BPW91/6-311G(d,p) levels.
- Analysis of linear correlations between experimental reactivity constants and theoretical electrostatic potential values (EPN).
- Solvent effect calculations using the Self-Consistent Isotherma l Polarizable Continuum Model (SCIPCM).
Main Results:
- An excellent linear correlation was found between experimental reactivity constants and EPN at para and meta positions.
- EPN serves as a reliable local reactivity descriptor for substituted benzene systems.
- Water solvent, via SCIPCM, enhances the polar substituent effect by approximately 30%.
- Intramolecular factors predominantly determine the relative values of sigma(0) constants.
Conclusions:
- The proposed computational method provides an accurate and efficient way to determine sigma(0) constants.
- EPN is a valuable descriptor for predicting reactivity in substituted benzenes.
- Solvent effects play a significant role in modulating substituent influences, and intramolecular effects are primary drivers of substituent constants.
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