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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 20, Number 5
BKCSDE 20(5)
May 20, 1999 

Transition-State Variation in the Solvolyses of Phenyl Chlorothionoformate in Alcohol-Water Mixtures
IN Sun Koo, Kiyull Yang, Dae Ho Kang, Hye Jin Park, Keumduck Kang, Ikchoon Lee
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.
577 - 580
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