Issue 5, 1986

Solvent effect on activation parameters for intramolecular general base-catalysed hydrolyses of salicylate esters and hydroxide ion-catalysed hydrolysis of methyl p-hydroxybenzoate

Abstract

The effects of varying concentrations of methyl alcohol, dimethyl sulphoxide, t-butyl alcohol, and acetonitrile on activation parameters for intramolecular general base-catalysed aqueous cleavages of methyl salicylate and alkaline hydrolysis of methyl p-hydroxybenzoate have been studied. The activation parameters for intramolecular general base-catalysed cleavage of phenyl salicylate was studied under varying concentrations of t-butyl alcohol, dimethyl sulphoxide, and acetonitrile. A significant enthalpy–entropy compensation effect is observed in the hydrolyses of these esters with change of t-butyl alcohol content into the reaction medium. The variation of acetonitrile concentration causes an enthalpy–entropy compensation effect only in the alkaline hydrolysis of methyl p-hydroxybenzoate. A significantly larger negative value of ΔS*, observed in the hydrolysis of methyl p-hydroxybenzoate at 90% H2O (v/v), compared with those for hydrolyses of salicylate esters obtained under an essentially similar solvent composition, is attributed to the difference in mechanisms for hydrolysis of these esters.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 2, 1986, 655-659

Solvent effect on activation parameters for intramolecular general base-catalysed hydrolyses of salicylate esters and hydroxide ion-catalysed hydrolysis of methyl p-hydroxybenzoate

M. N. Khan, I. L. Fatope, K. I. Isaac and M. O. Zubair, J. Chem. Soc., Perkin Trans. 2, 1986, 655 DOI: 10.1039/P29860000655

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