Abstract
The rates of the acid hydrolysis of potassium ethyl malonate in presence of KCl, NaCl, Li2SO4 and MgSO4 in water and in 50% by weight of dioxane—water mixture were measured. The concentration of the added salts covered the range 0–1M. A negative salt effect on the rate of the half-ester hydrolysis was observed. The applicability ofBrønsted's equation was tested and deviations found were explained as due among other reasons, to the operation of an iondipole type of interaction. The correlation between the hydration numbers as well as the radii of the cations of the added electrolytes and the reaction rate were discussed. The activation energy was found to increase with an increase of the concentration of electrolyte due to the relative changes in solvation of the transition state as a result of hydration of the electrolytes added. The thermodynamic properties of the activated complex were calculated and discussed as functions of the salt concentration. A remarkable linear compensation between ΔH ≠ and ΔS ≠ was found.
Zusammenfassung
Es wurde die Kinetik der Hydrolyse von Kaliumethylmalonat in Gegenwart von KCl, NaCl, Li2SO4 und MgSO4 (jeweils 0–1M) in Wasser und in 50% (w/w) Dioxan—Wasser untersucht. Es wurde ein negativer Salz-Effekt bezüglich der Hydrolysegeschwindigkeit des Halbesters beobachtet. Es werden sowohl Korrelationen zwischen Hydratationszahlen bzw. Ionenradien und der Reaktionsgeschwindigkeit, als auch zwischen Aktivierungsenergie und Elektrolytkonzentration diskutiert. Die thermodynamischen Parameter werden als Funktion der Salzkonzentration untersucht.
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Khalil, F.Y., Hanna, M.T. Kinetic salt effects in the acid hydrolysis of potassium ethyl malonate in water and in 50% dioxane—Water mixture. Monatshefte für Chemie 111, 841–849 (1980). https://doi.org/10.1007/BF00899249
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DOI: https://doi.org/10.1007/BF00899249