engleski

Solvolytic reactivity of various carboxylates

In order to provide new insights into SN1 solvolytic reactivity, stabilization effects of leaving groups and influences of solvent, the three-parameter LFER equation (Eq. 1) has been established on the basis of the log k vs. Ef correlation. In Eq. log k (25 °C) = sf (Nf + Ef), k is the solvolysis first-order rate constant, sf (slope of the correlation line) and Nf (negative intercept on the abscissa) are the nucleofuge-specific parameters, whereas Ef represents the electrofugality parameter of variously substituted benzhydrylium electrofuges. Employing these parameters and Eq.1, the solvolytic reactivity of any combination of an electrofuge and a nuclefuge in a given solvent can be predicted, which has already been demonstrated for various types of leaving groups. Solvolytic reactivities of various benzhydryl carboxylates in ethanol, acetone and acetonitrile binary mixtures with water have been studied by measuring solvolysis first-order rate constants from which the nucleofuge-specific parameters (Nf, and sf ) have been determined by using Eq. log k (25 °C) = sf (Nf + Ef). Furthermore, a quantum-chemical DFT-PCM model for calculating the reactivity of carboxylates has been developed. A very good correlation between the experimental and calculated reactivities of studied carboxylates has been obtained.

heterolysis; carboxylates; nucleofugality; model; DFT

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