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Quantification of CH···π interactions: implications on how substituent effects influence aromatic interactions.
Benjamin W Gung1, Bright U Emenike, Michael Lewis
1Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, USA. gungbw@muohio.edu
Chemistry (Weinheim an Der Bergstrasse, Germany)
|September 21, 2010
Summary
Attractive interactions between benzene rings and acetate groups were studied using a triptycene model. Acidity of the alpha-protons proved to be a better predictor of this interaction than Hammett constants.
Area of Science:
- Organic Chemistry
- Supramolecular Chemistry
- Physical Chemistry
Background:
- Non-covalent interactions are fundamental to molecular recognition and self-assembly.
- Understanding attractive forces between aromatic rings and functional groups is key to designing novel materials and catalysts.
- The triptycene framework provides a rigid scaffold to precisely orient interacting moieties.
Purpose of the Study:
- To experimentally quantify the attractive interaction between substituted benzene rings and α-substituted acetate groups.
- To compare the predictive power of Hammett constants and α-proton acidity for these interactions.
- To elucidate the electronic and structural factors governing these specific non-covalent interactions.
Main Methods:
- Utilizing a triptycene-based model system to isolate and study the interaction.
- Synthesizing a series of triptycene derivatives with varying substituents on the benzene ring and acetate group.
- Employing spectroscopic or computational methods to determine the strength of the attractive interaction.
- Correlating interaction strength with electronic parameters (Hammett constants) and acidity measurements.
Main Results:
- A significant attractive interaction was experimentally determined between the substituted benzene ring and the α-substituted acetate group.
- The interaction strength showed a good correlation with Hammett constants (R²=0.90).
- A much stronger correlation was observed between the interaction strength and the acidity of the α-protons (R²=0.98).
Conclusions:
- The acidity of α-protons is a superior descriptor for the attractive interaction compared to Hammett constants.
- This finding provides valuable insights into the nature of non-covalent interactions involving aromatic systems and carbonyl functionalities.
- The results can guide the rational design of molecules with tailored intermolecular interactions.
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