Kinetic Study of the Reaction of .ALPHA.-Bromoxylene and 2,4,6-Tribromophenol via Phase Transfer Catalysis at Low Alkalinity

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  • Wang Maw-Ling
    Department of Environmental Engineering, Hung-Kuang University
  • Yang Chau-Yun
    Department of Chemical Engineering, National Tsing Hua University
  • Hsieh Yu-Ming
    Department of Electronic Materials, Chin Min Institute of Technology

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  • Kinetic Study of the Reaction of α-Bromoxylene and 2,4,6-Tribromophenol via Phase Transfer Catalysis at Low Alkalinity
  • Kinetic Study of the Reaction of アルファ Bromoxylene and 2 4 6 Tribromophenol via Phase Transfer Catalysis at Low Alkalinity

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Abstract

The reaction of 2,4,6-tribromophenol and α-bromoxylenes (o-, p- and m-) catalyzed by tetrabutylammonium bromide was carried out in an alkaline solution of KOH of low concentration/organic solvent two-phase medium. The concentration of tetrabutylammonium 2,4,6-tribromophenoxide (ArOQ) is constant throughout the path of reaction while more than 98% of the catalyst exists as tetrabutylammonium 2,4,6-tribromophenoxide (ArOQ) in the organic phase. The mass transfer resistance of ArOQ between the two phases is negligible compared to the rate of organic-phase reaction. The reaction in the organic phase is a rate-determining step. A pseudo-first-order rate law is proposed to express the kinetic data. The effects of potassium hydroxide, organic solvents, agitation speed, amount of aqueous-phase reactant (2,4,6-tribromophenol), amount of catalyst, organic-phase reactant (α-bromoxylene), inorganic salts and temperature on the conversion are investigated in detail. It is found that the reaction rate is not well-correlated to the polarity of the organic solvent. The solvolysis effect, which concerns with the polarity and Lewis-base of the organic solvents, is used to explain the characteristics of the reaction satisfactorily at low alkaline concentration. The stability of carbonium ions of different α-bromoxylenes is used to explain their reaction rates satisfactorily.

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