Mechanism of base-catalyzed reactions in phase-transfer systems with poly(ethylene glycols) as catalysts. The isomerization of allylanisole

Ronny Neumann, Yoel Sasson

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Abstract

The mechanism of base-catalyzed reactions with poly(ethylene glycol) (PEG) as phase-transfer catalysts was studied by using the isomerization of allylanisole as a model reaction. The reaction kinetics showed the reaction to be chemical reaction controlled. The reaction system was a three-phase system consisting of an organic solvent phase, a PEG-potassium hydroxide complex phase, and a basic aqueous phase. The reaction mechanism included diffusion of the substrate from the solvent to the complex phase reaction and back diffusion of the product. The concentration of the aqueous phase is also important. When the aqueous phase is unsaturated there is no reaction. Concentrations above saturation increase rate because the basic complex becomes more potent under anhydrous conditions. The chain length and chain end moiety of the PEG catalysts have significant influence on the reaction rate. In general, short chain catalysts were more effective per gram but not per mole of catalyst. Etherification of the terminal hydroxyl group reduced activity. When alkoxide species were used as bases the trends were reversed, long chain catalysts being more effective and etherification increasing activity.

Original languageEnglish
Pages (from-to)3448-3451
Number of pages4
JournalJournal of Organic Chemistry
Volume49
Issue number19
Publication statusPublished - 1984

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Isomerization
Polyethylene glycols
Catalysts
Chain length
Reaction kinetics
Hydroxyl Radical
Organic solvents
Reaction rates
Chemical reactions
Substrates

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

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abstract = "The mechanism of base-catalyzed reactions with poly(ethylene glycol) (PEG) as phase-transfer catalysts was studied by using the isomerization of allylanisole as a model reaction. The reaction kinetics showed the reaction to be chemical reaction controlled. The reaction system was a three-phase system consisting of an organic solvent phase, a PEG-potassium hydroxide complex phase, and a basic aqueous phase. The reaction mechanism included diffusion of the substrate from the solvent to the complex phase reaction and back diffusion of the product. The concentration of the aqueous phase is also important. When the aqueous phase is unsaturated there is no reaction. Concentrations above saturation increase rate because the basic complex becomes more potent under anhydrous conditions. The chain length and chain end moiety of the PEG catalysts have significant influence on the reaction rate. In general, short chain catalysts were more effective per gram but not per mole of catalyst. Etherification of the terminal hydroxyl group reduced activity. When alkoxide species were used as bases the trends were reversed, long chain catalysts being more effective and etherification increasing activity.",
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T1 - Mechanism of base-catalyzed reactions in phase-transfer systems with poly(ethylene glycols) as catalysts. The isomerization of allylanisole

AU - Neumann, Ronny

AU - Sasson, Yoel

PY - 1984

Y1 - 1984

N2 - The mechanism of base-catalyzed reactions with poly(ethylene glycol) (PEG) as phase-transfer catalysts was studied by using the isomerization of allylanisole as a model reaction. The reaction kinetics showed the reaction to be chemical reaction controlled. The reaction system was a three-phase system consisting of an organic solvent phase, a PEG-potassium hydroxide complex phase, and a basic aqueous phase. The reaction mechanism included diffusion of the substrate from the solvent to the complex phase reaction and back diffusion of the product. The concentration of the aqueous phase is also important. When the aqueous phase is unsaturated there is no reaction. Concentrations above saturation increase rate because the basic complex becomes more potent under anhydrous conditions. The chain length and chain end moiety of the PEG catalysts have significant influence on the reaction rate. In general, short chain catalysts were more effective per gram but not per mole of catalyst. Etherification of the terminal hydroxyl group reduced activity. When alkoxide species were used as bases the trends were reversed, long chain catalysts being more effective and etherification increasing activity.

AB - The mechanism of base-catalyzed reactions with poly(ethylene glycol) (PEG) as phase-transfer catalysts was studied by using the isomerization of allylanisole as a model reaction. The reaction kinetics showed the reaction to be chemical reaction controlled. The reaction system was a three-phase system consisting of an organic solvent phase, a PEG-potassium hydroxide complex phase, and a basic aqueous phase. The reaction mechanism included diffusion of the substrate from the solvent to the complex phase reaction and back diffusion of the product. The concentration of the aqueous phase is also important. When the aqueous phase is unsaturated there is no reaction. Concentrations above saturation increase rate because the basic complex becomes more potent under anhydrous conditions. The chain length and chain end moiety of the PEG catalysts have significant influence on the reaction rate. In general, short chain catalysts were more effective per gram but not per mole of catalyst. Etherification of the terminal hydroxyl group reduced activity. When alkoxide species were used as bases the trends were reversed, long chain catalysts being more effective and etherification increasing activity.

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