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Reversible O-ylide formation in carbene/ether reactions
Pablo A Hoijemberg1, Robert A Moss, Karsten Krogh-Jespersen
1Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, USA.
The Journal of Physical Chemistry. A
|December 20, 2011
Summary
p-Nitrophenylchlorocarbene forms reversible O-ylides with ethers like THF. Spectroscopic and computational studies reveal the thermodynamics of these carbene-ether interactions.
Area of Science:
- Organic Chemistry
- Physical Chemistry
Background:
- Carbenes are reactive intermediates with diverse chemical applications.
- Understanding carbene reactivity with ethers is crucial for synthetic chemistry.
Purpose of the Study:
- To investigate the reversible reaction between p-nitrophenylchlorocarbene and various ethers.
- To characterize the resulting O-ylide intermediates and their thermodynamic properties.
Main Methods:
- UV-visible spectroscopy was employed to visualize and quantify O-ylide formation.
- Equilibrium constants (K(eq)) were determined at varying temperatures.
- Density functional theory (DFT) calculations were performed for structural and energetic analysis.
Main Results:
- Reversible O-ylide formation was observed with diethyl ether, di-n-propyl ether, and tetrahydrofuran (THF).
- Equilibrium constants ranged from 0.10 M⁻¹ (di-n-propyl ether) to 7.5 M⁻¹ (THF) at 295 K.
- Thermodynamic parameters (ΔH°, ΔS°, ΔG°) indicated favorable, albeit small, free energies for ylide formation.
Conclusions:
- p-Nitrophenylchlorocarbene reversibly interacts with ethers to form O-ylides.
- Spectroscopic and computational methods provide insights into carbene-ether complexation.
- The study elucidates the thermodynamic driving forces in these reversible reactions.
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