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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 18, Number 9
BKCSDE 18(9)
September 20, 1997 

 
Title
Stoichiometric Solvation Effects. Part 4. Product-Rate Correlations for Solvolyses of p-Methoxyphenyl Chloroformate in Alcohol-Water Mixtures
Author
In Sun Koo*, Kiyull Yang, Ja Chal Koo, Jong-keun Park, Ikchoon Lee
Keywords
Abstract
Solvolyses of p-methoxyphenyl chloroformate in water, D2O, CH3OD, 50% D2O-CH3OD, and in aqueous binary mixtures of acetone, ethanol and methanol are investigated at 25.0 ℃. Product selectivities are reported at 25 ℃ for a wide range of ethanol-water and methanol-water solvent compositions. The Grunwald-Winstein plots of first-order rate constants for p-methoxyphenyl chloroformate with YCl (based on 1-adamantyl chloride) show marked dispersions into three separate curves for the three aqueous mixtures with a small m value and a rate maximum for aqueous alcohol solvents. Third-order rate constants, kww, kaw, kwa and kaa were calculated from the observed kww and kaa values together with kaw and kwa calculated from the intercept and slope of the plot of 1/S vs. [alcohol]/[water]. The calculated rate constants, kcalc and mol % of ester agree satisfactorily with those of the observed rate constants, kobs and mol % of ester, supporting the stoichiometric solvation effect analysis. The kinetic solvent isotope effects determined in water and methanol are consistent with the proposed mechanism of the general base catalyzed carbonyl addition-elimination.
Page
1017 - 1021
Full Text
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