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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 8, Number 1
January 20, 1987 

The Solvolysis of Benzoyl Chloride in Water-Acetone Mixtures Under High Pressure
Jong-Gi Jee*, Taikyue Ree
By using a complete rate constant(ke) which treats a solvent (water) as a reactant, and a conventional rate constant(kc), which ignores the solvent in describing the rate, the parameters Δ V≠s, ΔH≠s, and ΔS≠s were introduced. These quantities represent the volume change, the enthalpy change, and the entropy change accompanying the electrostriction which occurs when solvent molecules condense on the activated complex. The authors measured the rates of the solvolysis of benzoyl chloride in water-acetone mixtures at 15°to 30℃ and 1 bar to 2500 bars. Applying the authors' theory to the experimental results, the parameters, ΔV≠s, ΔH≠s, and ΔS≠ s were evaluated, and it was found that they are all negative, indicating that water dipoles condense on the activated complex. They also proposed the following equations: ΔH≠c = ΔH≠e + ΔH≠s and ΔS≠c = ΔS≠e + ΔS≠s, where Δ H≠c and ΔS≠c are the activation enthalpy change and the activation entropy change for the conventional reaction rate, respectively, and Δ H≠e and ΔS≠e are the corresponding quantities for the complete reaction rate. The authors proposed that for the SN1 type, all the quantities, ΔH≠s, ΔS≠s, ΔH≠e and ΔS≠e are comparatively large, and for the SN2 type, these quantities are smaller than for the SN1 type, and occasionally the case ΔS≠e < 0 occurs. Using these criteria, the authors concluded that at high temperature, high pressure and for a high water content solvent, the SN1 type mechanism predominates whereas in the reversed case the SN2 type predominates.
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