Mechanism of Regioselective Ring-Opening Reactions of 1,2-Epoxyoctane Catalyzed by Tris(pentafluorophenyl)borane

A Combined Experimental, Density Functional Theory, and Microkinetic Study

Ying Yu, Youlong Zhu, Mihir N. Bhagat, Arjun Raghuraman, Kurt F. Hirsekorn, Justin M Notestein, Sonbinh T. Nguyen, Linda J. Broadbelt

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

A nonconventional, water-mediated catalytic mechanism was proposed to explain the effects of residual water on the reactivity and regioselectivity of tris(pentafluorophenyl)borane catalyst in the ring-opening reaction of 1,2-epoxyoctane by 2-propanol. This nonconventional mechanism was proposed to operate in parallel with conventional Lewis acid-catalyzed ring-opening. Microkinetic modeling was conducted to validate the proposed reaction mechanism, with all kinetic and thermodynamic parameters derived from density functional theory (DFT) calculations. Experimental data at a variety of temperatures and water contents were captured by the model after adjustments within reasonable limits set by experimental benchmarking and accuracy of theory of a small subset of parameters. In addition, the microkinetic model was able to generate accurate predictions at reaction conditions that were not used for parameter estimation. Detailed analysis of the net reaction rates showed that >95% of the reaction flux passed through conventional Lewis-acid pathways at water levels <500 ppm, even though the borane-epoxide adduct never accounted for more than 30% of the catalyst speciation under reaction conditions. With increasing water, as much as 80% of the reaction flux utilized water-mediated reaction intermediates. Within the water-mediated mechanisms, different hydrogen bond acceptors (HBAs) influenced the reaction regioselectivity. Overall, this validated mechanism and microkinetic model provided better understanding of industrially important ring-opening catalysis with this catalyst in the presence of water and could facilitate future improvement of catalyst regioselectivity and reactivity.

Original languageEnglish
JournalACS Catalysis
DOIs
Publication statusAccepted/In press - Jan 1 2018

Fingerprint

Density functional theory
Regioselectivity
Water
Lewis Acids
Catalysts
Boranes
Fluxes
Reaction intermediates
2-Propanol
Acids
Epoxy Compounds
Propanol
Benchmarking
Water levels
Parameter estimation
Water content
Catalysis
Reaction rates
1,2-epoxyoctane
tris(pentafluorophenyl)borane

Keywords

  • catalysis
  • DFT
  • mechanism
  • microkinetic modeling
  • regioselectivity
  • ring-opening reactions

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

Cite this

Mechanism of Regioselective Ring-Opening Reactions of 1,2-Epoxyoctane Catalyzed by Tris(pentafluorophenyl)borane : A Combined Experimental, Density Functional Theory, and Microkinetic Study. / Yu, Ying; Zhu, Youlong; Bhagat, Mihir N.; Raghuraman, Arjun; Hirsekorn, Kurt F.; Notestein, Justin M; Nguyen, Sonbinh T.; Broadbelt, Linda J.

In: ACS Catalysis, 01.01.2018.

Research output: Contribution to journalArticle

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abstract = "A nonconventional, water-mediated catalytic mechanism was proposed to explain the effects of residual water on the reactivity and regioselectivity of tris(pentafluorophenyl)borane catalyst in the ring-opening reaction of 1,2-epoxyoctane by 2-propanol. This nonconventional mechanism was proposed to operate in parallel with conventional Lewis acid-catalyzed ring-opening. Microkinetic modeling was conducted to validate the proposed reaction mechanism, with all kinetic and thermodynamic parameters derived from density functional theory (DFT) calculations. Experimental data at a variety of temperatures and water contents were captured by the model after adjustments within reasonable limits set by experimental benchmarking and accuracy of theory of a small subset of parameters. In addition, the microkinetic model was able to generate accurate predictions at reaction conditions that were not used for parameter estimation. Detailed analysis of the net reaction rates showed that >95{\%} of the reaction flux passed through conventional Lewis-acid pathways at water levels <500 ppm, even though the borane-epoxide adduct never accounted for more than 30{\%} of the catalyst speciation under reaction conditions. With increasing water, as much as 80{\%} of the reaction flux utilized water-mediated reaction intermediates. Within the water-mediated mechanisms, different hydrogen bond acceptors (HBAs) influenced the reaction regioselectivity. Overall, this validated mechanism and microkinetic model provided better understanding of industrially important ring-opening catalysis with this catalyst in the presence of water and could facilitate future improvement of catalyst regioselectivity and reactivity.",
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AU - Raghuraman, Arjun

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