ADDUCT FORMATION OF A URANYL ISOXAZOLONATE WITH ORGANOPHILIC NEUTRAL OXODONORS

The extraction behaviour of dioxo-uranium(VI) from aqueous HNO3 with 3 -phenyl-4-benzoyl-5-isoxazolone (HPBI) and oxodonors with varying basi cities viz. di-n-butyl octanamide, tri-n-butyl phosphate and tri-n-oct ylphosphine oxide has been investigated in xylene medium. The logarith m of the extraction constant for the species UO2(PBI)(2) . H2O is esti mated as 1.41 which is distinctly larger as compared to the correspond ing values for 2-thenoyltrifluoroacetone (-2.40) and 1-phenyl-3-methyl -4-benzoyl-5-pyrazolone (0.48) systems. The logarithm of the equilibri um constants for adduct formation are found to be 4.87 (DBOA), 5.13 (T BP) and 8.70 (TOPO). The overall extraction constants follow an invers e correlation with the pKa values of the beta-diketones while the addu ct formation constants vary linearly with the basicities of the oxodon ors, Steric factors have been found to play a significant role in the co-ordination of the oxodonors to the uranyl beta-diketonates where th e carbonyl group is a part of the heterocyclic ring.