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Transition-State Variation in the Solvolyses of Phenyl Chlorothionoformate in Alcohol-Water Mixtures

  • 구인선;양기열;강대호;박혜진;강금덕;이익춘
    • Bulletin of the Korean Chemical Society
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    • v.20 no.5
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    • pp.577-580
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    • 1999

  • Solvolyses of phenyl chlorothionoformate in water, D2O, CH3OD, 50% D2O-CH3OD, and in aqueous binary mixtures of acetone, ethanol and methanol are investigated at 25.0℃. The Grunwald-Winstein plots of firstorder rate constants for phenyl chlorothionoformate with Ycl (based on 2-adamantyl chloride) show a dispersion phenomenon, and also the extended Grunwald-Winstein plots show a poor correlation for the solvolyses of phenyl chlorothionoformate. The ring parameter (I) has been shown to give considerable improvement when it is added as an hI term to the original and extended Grunwald-Winstein correlations. The dispersions in the Grunwald-Winstein correlations in the present studies are caused by the conjugation between the reaction center and the aromatic ring in the vicinity of the reaction center. This study has shown that the magnitude of l and m values associated with a change of solvent composition leads to predict the SN2 transition state. The kinetic solvent isotope effects determined in deuterated water and methanol are consistent with the proposed mechanism of the general base catalyzed SN2 mechanism.

  • https://doi.org/10.5012/bkcs.1999.20.5.577 인용 PDF

Segregation resistance of high fluidity concrete depending on addition method of thixotropy-inducing materials (고유동 콘크리트의 고요변성 부여 물질 혼합방법에 따른 재료분리 방지 여부)

  • Kim, Young-Ki;Lee, Yu-Jeong;Heo, Jun-Ho;Han, Dongyeop
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2022.11a
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    • pp.113-114
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    • 2022

  • The aim of the research is to evaluate the segregation resistivity of the mixture conditions by changing the PVA and borax solutions for thixotropic property on concrete mixture. Since the water addition caused by producing solutions of PVA and borax induces segregation of the concrete mixture, the unit water was reduced by replacing the water amount for PVA and borax solution. By replacing the water from PVA and borax solutions, the segregation was prevented with prefixed concrete mix design and thixotropic properties were also occurred.

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