Kinetics and mechanism of the reactions of uranyl ion and β-diketones in methanol–water (9 : 1 v/v)
Abstract
The rates of ketonization and enolization together with the enol to keto ratios of 1,1,1-trifluoropentane-2,4-dione (Htfpd) and 4,4,4-trifluoro-1-(2-thienyl)butane-1,3-dione (Htftbd) have been determined in a range of methanol–water solutions. The equilibrium constants for formation of [UO2(tfpd)]+ and [UO2(tftbd)]+ have been determined in methanol–water solutions (9 : 1 v/v). The kinetics and mechanisms of the reactions of uranyl ion with pentane-2,4-dione (Hpd), Htfpd, and Htftbd in methanol–water solutions (9 : 1 v/v) have been investigated. The [UO2]2+ ion reacts with the enol tautomer of Hpd with a rate constant of 4 928 ± 727 dm3 mol–1 s–1, while it reacts with the keto tautomer with a rate constant of 18.1 ± 0.5 dm3 mol–1 s–1. However, [UO2]2+ reacts exclusively with the enol tautomers of Htfpd and Htftbd with rate constants estimated to be 1 000 dm3 mol–1 s–1.