Determination of keto–enol equilibrium constants and the kinetic study of the nitrosation reaction of β-dicarbonyl compounds

Abstract

The keno–enol equilibrium constants of acetylacetone, ethyl acetoacetate and ethyl benzoylacetate in water at 25 °C are determined by studying the influence of surfactants on their UV–VIS spectra, following the method applied to benzoylacetone published recently. These measured equilibrium constants are used to obtain the reactivity of the ketones towards several nitrosating agents. For this end, the nitrosation reaction of benzoylacetone, acetylacetone, ethyl acetoacetate and ethyl benzoylacetate are studied in aqueous acidic solution in the presence and absence of Cl^-, Br^- or SCN^-. Analysis of the kinetic data indicates that the rate-limiting step is, in every case, the reaction of the enol.