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Basicity of some phosphines in THF.
Andrew Streitwieser1, Arlene E McKeown, Faraj Hasanayn
1Department of Chemistry, University of California, Berkeley, Berkeley, California 94720-1460, USA. astreit@berkeley.edu
Organic Letters
|March 25, 2005
Summary
Researchers studied phosphine reactions with acidic indicators, forming ion pairs and free ions. Molecular orbital computations supported the pKa of tribenzylphosphine, revealing limitations in the Fuoss equation for ion pair dissociation.
Area of Science:
- Physical Chemistry
- Organometallic Chemistry
Background:
- Understanding the behavior of phosphines in solution is crucial for various chemical applications.
- Ion pair and free ion formation are key phenomena in electrolyte solutions and reaction mechanisms.
Purpose of the Study:
- To investigate the reaction products of phosphines with acidic indicators.
- To determine the pKa of tribenzylphosphine and validate it using computational methods.
- To assess the applicability of the Fuoss equation for describing ion pair dissociation involving phosphines.
Main Methods:
- Reaction of phosphines with an acidic indicator.
- Determination of pKa values.
- Molecular Orbital (MO) computations.
- Analysis of ion pair dissociation using the Fuoss equation.
Main Results:
- The reaction yields both ion pairs and free ions.
- MO computations indicate that the determined pKa for tribenzylphosphine is reasonable.
- A significant limitation of the Fuoss equation was identified for the dissociation of these ion pairs.
Conclusions:
- Phosphine reactions with acidic indicators produce a mixture of ion pairs and free ions.
- Computational chemistry supports the experimental pKa value for tribenzylphosphine.
- The Fuoss equation may not accurately describe ion pair dissociation in all phosphine-related systems.