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Kinetic Explanation for the Temperature Dependence of the Regioselectivity in the Hydroformylation of Neohexene
Author(s) -
Güven Sabriye,
Nieuwenhuizen Marko M. L.,
Hamers Bart,
Franke Robert,
Priske Markus,
Becker Marc,
Vogt Dieter
Publication year - 2014
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201300818
Subject(s) - hydroformylation , chemistry , hydrogenolysis , regioselectivity , aldehyde , catalysis , medicinal chemistry , denticity , alkyl , ligand (biochemistry) , rhodium , photochemistry , organic chemistry , metal , biochemistry , receptor
The kinetics of Rh‐catalyzed neohexene hydroformylation were investigated with the bulky monodentate ligand tris(2,4‐di‐ tert ‐butylphenyl)phosphite. The hydrogenolysis of the Rh–acyl intermediate was identified as the rate‐limiting step for both the linear and the branched aldehydes. Rate equations for both aldehydes were derived and kinetic parameters were estimated. Increased aldehyde linearity at higher temperatures, frequently observed in hydroformylation, was elucidated by deuterioformylation experiments. These showed that at 100 °C the formation of linear Rh–alkyl was more reversible than the formation of the branched derivative. The ratio of linear to branched Rh–acyl species was determined by in situ high‐pressure IR spectroscopy experiments, which allowed the difference in the activation energies for the hydrogenolysis steps towards the aldehyde isomers to be quantified. The hydrogenolysis of Rh–acyl was found to be the step that caused the greatest temperature effect on the regioselectivity.