Kinetics and mechanism of the reaction of uranyl ion with thenoyltrifluoroacetone

Abstract

The kinetics and equilibrium of the reaction of thenoyltrifluoroacetone and uranyl ion [UO₂]²⁺ to form the mono complex have been studied in aqueous solution at 25 °C and 1.0 mol dm^–3 ionic strength. The value of the equilibrium constant, K₁ for reaction (i) where HA represents the undissociated form of thenoyltrifluoroacetone, [UO₂]²⁺+ HA ⇌[UO₂E]⁺+ H⁺(i) is 0.14 ± 0.02. The kinetic data are consistent with a scheme in which [UO₂]²⁺ reacts with the enol form of the ligand. The rate constants for reaction of [UO₂]²⁺ with HE, the undissociated form of the enol tautomer, and with E^– the enolate ion are 1 × 10⁴ and 3 × 10⁵ dm³ mol^–1 s^–1 respectively.