Synergistic extraction of uranyl ion with β-diketones and sulphoxides

Distribution measurements of the synergistic extraction of uranyl ion with β-diketones and sulphoxide donors indicate that the long-chain aliphatic sulphoxides are ten times more powerful as synergists than the aromatic sulphoxides. Methods of estimating the relative base strength of the donors by i.r. and N.M.R. studies of the donor hydrates are described and the results have been correlated with the equilibrium constant of the synergistic reaction. For a given sulphoxide donor, the synergistic enhancement seems to be affected by the various substituents changing the acidity of the β-diketone. From the values of enthalpy and entropy factors derived for these systems by distribution measurements at different temperatures, the greater stability of the complexes with aliphatic sulphoxide donors has been attributed to the entropy factor.