Journal article

pH Dependent Mechanisms of Hydrolysis of 4-Nitrophenyl β-D-Glucoside

Amani Alhifthi, Spencer Williams

American Chemical Society (ACS)

Abstract

1,2-trans-Glycosides hydrolyze through a range of mechanisms under conditions of different pH, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect (k(H3O+)/k(D3O+) = 0.63) in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region extrapolated to zero buffer concentration show a small inverse solvent isotope effect k(H2O)/k(D2O) = 1.1 and a positive entropy of activation (DS‡ = 3.07 cal mol–1 K–1), which is c..

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University of Melbourne Researchers