Nucleophilic substitution reaction of alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chloride in alcohol-water mixtures

Solvolyses of alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chloride in H2O, D2O, CH3OD, 50% D2O-CH3OD, and in aqueous binary mixtures of acetone, dioxane, ethanol and methanol are investigated at 25.0 degrees C. The Grun wald-Winstein plots of first-order rate constants for alpha-methoxy-alpha-( trifluoromethyl)phenylacetyl chloride with Y-CI show a dispersion phenomeno n. Solvent nucleophilicity N has been shown to give considerable improvemen t when it is added as an IN term to the original Grunwald-Winstein for the solvolyses of alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chloride. T he dispersions in the Grunwald-Winstein correlations in the present studies are caused by solvent nucleophilicity. The magnitude of I and m values ass ociated with a change of solvent composition predicts the associative S(N)2 transition state. The kinetic solvent isotope effects determined in deuter ated water and methanol are consistent with the proposed mechanism of the g eneral base catalyzed associative S(N)2 or SAN mechanism for the of alpha-m ethoxy-alpha-(trifluoromethyl)phenylacetyl chloride.