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Published on: July 19, 2019
H-bonding-assisted substituent effect
Tadeusz M Krygowski1, Joanna E Zachara-Horeglad, Marcin Palusiak
1Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland. tmkryg@chem.uw.edu.pl
The Journal of Organic Chemistry
|June 26, 2010
Summary
Intramolecular noncovalent interactions, like hydrogen and lithium bonding, influence substituent properties in conjugated systems. These interactions modulate electron-donating and withdrawing effects, similar to the Hammett substituent effect.
Area of Science:
- Physical Chemistry
- Computational Chemistry
- Organic Chemistry
Background:
- Intramolecular noncovalent interactions, such as hydrogen bonding (H-bonding) and lithium bonding (Li-bonding), play a crucial role in molecular systems.
- Salicylaldehyde, o-hydroxy Schiff base, o-nitrosophenol, and their lithium analogues are key examples of systems exhibiting intramolecular resonance-assisted interactions.
- Understanding these interactions is vital for predicting and controlling molecular properties.
Purpose of the Study:
- To investigate the influence of intramolecular noncovalent interactions (H-bonding and Li-bonding) on substituent properties.
- To analyze how these interactions affect electron delocalization through resonance (mesomeric) effects.
- To explore the applicability of a Hammett-like substituent effect model to these noncovalently bonded systems.
Main Methods:
- Theoretical investigation of molecular systems including salicylaldehyde, o-hydroxy Schiff base, o-nitrosophenol, and their lithium analogues.
- Analysis of intramolecular noncovalent interactions (A-H...B and A-Li...B).
- Evaluation of pi-electron delocalization within conjugated systems.
Main Results:
- Demonstrated that intramolecular noncovalent interactions significantly influence substituent properties.
- Showed that these interactions modulate the electron-donating and electron-withdrawing characteristics of substituents.
- Established a correlation between noncovalent interactions, pi-electron delocalization, and a Hammett-like substituent effect.
Conclusions:
- Intramolecular noncovalent interactions are key modulators of substituent electronic effects in conjugated systems.
- The observed effects can be effectively described using a Hammett-like substituent parameter approach.
- This study provides insights into the interplay between noncovalent bonding and electronic communication in organic molecules.
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