Solvent effect on activation parameters for intramolecular general base-catalysed hydrolyses of salicylate esters and hydroxide ion-catalysed hydrolysis of methyl p-hydroxybenzoate
- 1 January 1986
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 5,p. 655-659
- https://doi.org/10.1039/p29860000655
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.Keywords
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