Enolization of Benzoylacetone in Aqueous Surfactant Solutions:  A Novel Method for Determining Enolization Constants

Abstract

The keto−enol tautomerism of benzoylacetone (1-phenyl-1,3-butadione) in aqueous acidic solution at 25 °C was investigated by studying the influence of anionic, cationic, and nonionic surfactants in the UV−vis spectra of benzoylacetone. The percentage of the enol tautomer was found to increase abruptly at surfactant concentration above the critical micelle concentration (cmc). A model is proposed to quantitatively interpret the experimental results, which allows for the determination of the enolization constant in water, K E, and in micellar, pseudophases; the binding constant of the enol tautomer to micelles, K s; and the extinction coefficients of the ketonic and enolic forms, ε, of benzoylacetone. The formation of the enolate in the absence and presence of micelles in basic media was also studied. The acidity constants of the enolic, and ketonic, forms of benzoylacetone have been determined.

Mechanism for stabilization of the molten globule state of papain by sodium n-alkyl sulfates: Spectroscopic and calorimetric approaches

“…Sodium decyl sulfate (SDeS) and sodium tetradecyl sulfate (STS) were obtained from Merck and Lancet Co., respectively. The concentrations of the n-alkyl sulfates used in all experiments were under the critical micelle concentrations (CMC) and critical aggregation concentration (CAC) [25,26]. Here, the actual ranges of n-alkyl sulfates concentrations are 0-1.5 mM SOS, 0-0.8 mM SDeS, 0-0.18 mM SDS, and 0-0.07 mM STS.…”

Cooperative α-helix formation of β-lactoglobulin induced by sodium n-alkyl sulfates

“…Other chemicals were of reagent grade. The concentrations of n-alkyl sulfates used in all experiments were under the critical micelle concentrations (CMC) and critical aggregation concentration (CAC) [50,51].…”

Comparison of the conformational stability of the non-native α-helical intermediate of thiol-modified β-lactoglobulin upon interaction with sodium n-alkyl sulfates at two different pH

“…Sodium decyl sulfate (SDeS) and sodium tetradecyl sulfate (STS) were obtained from Merck and Lancet Co., respectively. The concentrations of n-alkyl sulfates used in all experiments were under the critical micelle concentration (CMC) and critical aggregation concentration (CAC) [45,46]. TNB-β-LG was prepared by titrating the thiol group of β-LG at 0.4 mg ml −1 with 0.4 mM DTNB in 1.0 M Gdn-HCl and 10 mM Tris-HCl buffer at pH 7.5 and 10 mM HCl at pH 2.…”