English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Open

The pH-independent hydrolysis of four esters, p-methoxyphenyl 2,2-dichloroethanoate (1a), p-methoxyphenyl 2,2-dichloropropanoate (1b), p-methoxyphenyl 2,2-dichlorobutanoate (1c), and p-methoxyphenyl 2,2-dichloropentanoate (1d), in dilute aqueous solution has been studied as a function of the molality of added cosolutes ethanol, 1-propanol, and 1-butanol. The rate constants for the neutral hydrolysis decrease with increasing cosolute concentration. These kinetic medium effects respond to both the hydrophobicity of the ester and of the monohydric alcohol. The observed rate effects were analyzed using both a thermodynamic and a kinetic model. The kinetic model suggests a molecular picture of a hydrophobically stabilized encounter complex, with equilibrium constants K(ec) often smaller than unity, in which the cosolute blocks the reaction center of the hydrolytic ester for attack by water. The formation of these encounter complexes leads to a dominant initial-state stabilization as follows from the thermodynamic model. Decreases in both apparent enthalpies and entropies of activation for these hydrolysis reactions correspond to unfavorable enthalpies and favorable entropies of complexation, which confirms that the encounter complexes are stabilized by hydrophobic interactions.

Kinetic Evidence for Hydrophobically Stabilized Encounter Complexes Formed by Hydrophobic Esters in Aqueous Solutions Containing Monohydric Alcohols