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Intraparticle Diffusional versus Site Effects on Reaction Pathways in Liquid‐Phase Cross Aldol Reactions
Author(s) -
Ponnuru Koushik,
Manayil Jinesh C.,
Cho Hong Je,
Fan Wei,
Wilson Karen,
Jentoft Friederike C.
Publication year - 2018
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201701219
Subject(s) - aldol reaction , aldol condensation , chemistry , regioselectivity , benzaldehyde , organic chemistry , catalysis , dehydration reaction
Abstract Chemo‐ and regioselectivity in a heterogeneously catalyzed cross aldol reaction were directed by tuning the nature of the sites, textural properties, and reaction conditions. Catalysts included sulfonic acid‐functionalized resins or SBA‐15 with varying particle size or pore diameter, H‐BEA zeolites, and Sn‐BEA zeotype; conditions were 25 °C to 170 °C in organic media. Benzaldehyde and 2‐butanone yielded branched (reaction at ‐CH 2 ‐ of butanone) and linear (reaction at ‐CH 3 ) addition and condensation products; and fission of the branched aldol led to β‐methyl styrene and acetic acid. Strong acids promoted the dehydration step, and regioselectivity originated from preferred formation of the branched aldol. Both, resins and functionalized SBA‐15 materials yielded predominantly the branched condensation product, unless particle morphology or temperature moved the reaction into the diffusion‐limited regime, in which case more fission products were formed, corresponding to Wheeler Type II selectivity. For H‐form zeolites, fission of the branched aldol competed with dehydration of the linear aldol, possibly because weaker acidity or steric restrictions prevented dehydration of the branched aldol.