Solvent-Induced Reversal of Activities between Two Closely Related Heterogeneous Catalysts in the Aldol Reaction

Date
2013-01-01
Authors
Kandel, Kapil
Althaus, Stacey
Peeraphatdit, Chorthip
Kobayashi, Takeshi
Trewyn, Brian
Pruski, Marek
Slowing, Igor
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Ames Laboratory
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Chemistry
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Abstract

The relative rates of the aldol reaction catalyzed by supported primary and secondary amines can be inverted by 2 orders of magnitude, depending on the use of hexane or water as a solvent. Our analyses suggest that this dramatic shift in the catalytic behavior of the supported amines does not involve differences in reaction mechanism, but is caused by activation of imine to enamine equilibria and stabilization of iminium species. The effects of solvent polarity and acidity were found to be important to the performance of the catalytic reaction. This study highlights the critical role of solvent in multicomponent heterogeneous catalytic processes.

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Reprinted (adapted) with permission from ACS Catalysis 3 (2013): 265, doi:10.1021/cs300748g. Copyright 2014 American Chemical Society.

Keywords
mesoporous silica nanoparticles, aldol condensation, enamine catalysis, solvent effects, solid-state NMR
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