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Activation in prochiral reaction assemblies on Pt(111)
Marc-André Laliberté1, Stéphane Lavoie, Bjørk Hammer
1Département de Chimie, Université Laval, Québec, QC, Canada G1K 7P4.
Journal of the American Chemical Society
|April 3, 2008
Summary
Trifluoroacetophenone (TFAP) forms hydrogen-bonded dimers and trimers on platinum surfaces. This self-assembly behavior may explain the limited rate enhancement observed in the enantioselective hydrogenation of similar molecules.
Area of Science:
- Surface science and catalysis
- Organic chemistry
Background:
- Trifluoroacetophenone (TFAP) is a prochiral ketone relevant to asymmetric catalysis.
- Enantioselective hydrogenation of ketones is crucial for synthesizing chiral molecules.
- Cinchona alkaloids are commonly used chiral modifiers on platinum catalysts.
Purpose of the Study:
- To investigate the self-assembly of TFAP on a Pt(111) surface.
- To propose a model for TFAP interaction that explains observed catalytic outcomes.
- To understand the role of molecular assembly in enantioselective hydrogenation reactions.
Main Methods:
- Experimental observation of TFAP adsorption and assembly on Pt(111) at room temperature.
- Theoretical proposal linking TFAP self-assembly to catalytic interactions.
- Analysis of TFAP activation in homomolecular assemblies versus diastereomeric complexes.
Main Results:
- TFAP forms C=O···H-C bonded dimers and trimers on Pt(111) at room temperature.
- These self-assembled structures are proposed to mimic interactions in catalytic systems.
- The observed self-assembly suggests similar TFAP activation at racemic and chiral sites.
Conclusions:
- The self-assembly of TFAP on platinum surfaces provides a model for understanding prochiral carbonyl-chiral modifier interactions.
- This molecular assembly mechanism offers a potential explanation for the lack of significant rate enhancement in the Orito reaction for alpha-phenyl ketones.
- Understanding supramolecular organization is key to optimizing enantioselective catalytic processes.
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