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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 17, Number 11
BKCSDE 17(11)
November 20, 1996 

Solvent Effects on the Solvolysis of 1-(4-Methoxyphenyl)-l-phenyl-2,2,2-trifiuoroethyl Chloride. Influence of an Electron-Withdrawing α-Substituent on Carbonium Ion Center
Jeong-Min Kweon, Sung-Hong Kim, Soo-Dong Yoh*
Solvolysis rates of 1-(4-methoxyphenyl)-l-phenyl-2,2,2-trifiuoroethyl chloride (1) and 1-(4-methoxyphenyl)-1-phenylethyl chloride (2) were measured in a variety of aqueous binary solvents, and the solvent effect was treated with the Grunwald-Winstein equation. The solvent effect on the solvolysis of 1 failed to give a single linear correlations using the ordinary Y or YCl, but exhibited the wide split pattern which could not be related to the solvent nucleophilicity. The improved correlations with YBnCl and extended dual-parameter treatment, log (k/k0)=mYCl+hI (mΔYΔ), were observed for the solvolysis of 1. These results suggest that the incipient cationic charge in the solvolysis of 1 is delocalized strongly into the aryl-rings in the transition state. While the solvent effect on the solvolysis of 2 is better correlated with Y or YCl than YBnCl but the linearity is not satisfactory. The correlation is comparably improved by the use of the extended Grunwald-Winstein equation, log (k/k0)=0.81YCl+0.26NOTs (R=0.994, SD=±0.12), indicating the cationic charge of reaction center of 2 was localized mostly in the transition state.
1056 - 1061
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