Effects of pressure on reversed micellar systems. Rates of the keto–enol transformation of pentane-2,4-dione

Abstract

The rates of the keto–enol tautomerism of pentane-2,4-dione (acetylacetone) have been measured spectrophotometrically in reversed micellar systems of dodecylammonium propionate (DAP) and dodecylammonium butyrate (DAB) at pressures up to 98.1 MPa. The rates were enhanced by pressure and surfactants, especially at concentrations above the ‘operational’ critical micelle concentration. The activation volumes of the reaction (ΔV) in various systems have been determined and used to estimate the polarity of the microscopic reaction environment. On the basis of the kinetic and thermodynamic data obtained, the formation of reversed micelles as a reaction field is discussed.