STERIC EFFECT OF SUBSTITUENTS ON THE EXTRACTION OF LANTHANOIDS(III) WITH -,ISO-AND-TERT-)BUTYLBENZOYL-N-PHENYLHYDROXYLAMINE

N-p-(n-, iso- and tert-)Butylbenzoyl-N-phenylhydroxylamine (HL) was sy nthesized to evaluate the steric effect of the substituent on the mutu al extraction separation of representative lanthanoids(III) (Ln). Lant hanoids(III) were all found to be extracted with compounds as self-add ucts of the form LnL(3)(HL)(2). It was found that the structure of the substituents in N-p-butylbenzoyl-substituted N-phenylhydroxylamine is closely related to the separation factor for the pair of Yb/Eu. The s eparation factors for a pair of Eu/Yb with these compounds decreased i n the order of tert-butyl derivative > iso- > n-, with a decreasing Ta ft's E-s value, that is, with an increasing steric effect of the subst ituent group. The correlation between the separation factor and the st ereochemical shape of the substituent was also investigated. (C) 1997 Published by Elsevier Science B.V.