Kinetic Studies of Solvolysis. IX. The S<SUB>N</SUB>l-type Cleavage of <I>t</I>-Butyl <I>p</I>-Substituted-phenyl Ethers and Optically-active α-Phenethyl Phenyl Ether by Hydrogen Halides in a Phenol-Dioxane Solvent

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概要

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• 1) Hydrogen chloride cleaves <I>t</I>-butyl phenyl ether at 70.0°C in 20 wt.% phenol-dioxane. The reaction is kinetically first-order in each reactant. The second-order rate constants show an increase with increasing phenol concentrations, and <I>p</I>-nitrophenol accelerates the reaction.<BR>2) The hydrogen bromide cleavage of <I>t</I>-butyl phenyl ether at 19.2°C in 20wt. % phenol-dioxane gives a second-order rate constant greater than that of hydrogen chloride.<BR>3) The rate sequence of the hydrogen chloride cleavage of <I>t</I>-butyl <I>p</I>-substituted-phenyl ethers at 70.0°C in 20 wt.% phenol-dioxane is H><I>p</I>-CH<SUB>3</SUB>><I>p</I>-NO<SUB>2</SUB>><I>p</I>-Cl, and there is no linear relationship between those rate constants and Hammett'σ constants.<BR>4) The hydrogen chloride cleavage of (+)-α-phenethyl phenyl ether at 30.0°C in 50.0 wt.% phenol-dioxane obeys good second-order kinetics for both polarimetric and titrimetric runs. The value of the polarimetric rate constant exceeds that of the titrimetric constant, and from the final reading of the polarimetric run it has been concluded that the α-phenethyl chloride produced in the cleavage partly retained the configuration.<BR>5) It has been concluded that the hydrogen halide cleavage of those phenyl ethers in phenol-dioxane proceeds through the protonated ether produced by a rapid equilibration between hydrogen halide and those ethers, and that the protonated ether reacts by an S<SUB>n</SUB><I>i</I>-like mechanism. For the cleavage of the opticallyactive ethers, a detailed mechanism involving two parallel series of cleavage reactions of antipodal protonated ethers has been suggested wherein the partial racemization of the product is explained as resulting from the interconversion between the antipodal intermediates. For each series of S<SUB>n</SUB><I>i</I>-type reactions, the possibility of a two-stage or three-stage mechanism has been discussed.

• 社団法人 日本化学会の論文

著者

• OKAMOTO K.

  Department of Polymer Science and Engineering, Kyoto Institute of Technology

• Takeuchi Ken-ichi

  Department Of Energy And Hydrocarbon Chemistry Graduate School Of Engineering Kyoto University

• Shingu Haruo

  Department of Fuel Chemistry Faculty of Engineering Kyoto University

• Takeuchi Ken-ichi

  Department of Fuel Chemistry Faculty of Engineering Kyoto University

• Okamoto K.

  Department of Pathology, Faculty of Medicine, Kyoto University

• Okamoto Kunio

  Department of Fuel Chemistry Faculty of Engineering Kyoto University

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