Abstract
The relationship between extractant stereochemistry and their extraction performance has only poorly been established. In order to address a part of this concern, we investigated the Pu(IV) liquid-liquid extraction (LLE) by using the N,N-di-(2- ethylhexyl)butyramide (DEHBA), as well as those of its position isomers. DEHBA (ββ-isomer) and N-(2-ethylhexyl)-N-(oct-3- yl)butyramide (EHOBA or αβ-isomer) were synthesized as amixture of stereoisomer or stereoenriched (R,S)- and (S,S)- diastereoisomers, and were all assessed for Pu$^{IV}$ LLE. The results showed that both the position and the stereoisomerism of the aliphatic substituents affect Pu$^{IV}$ complexation and extraction. We found that Pu extraction is lowered by factor 2 to 4 when the ethyl branching group is closer to the complexing site. UVvis spectroscopy showed that this extraction decrease was affected by steric hindrance inducing a deprivation of Pu inner sphere complex. Effect of stereoisomerism is highlighted for branching closer to the complexing site (α-position). Enantiopure DEHBA stereoisomers provided similar Pu extraction, whereas a slight decrease could be noticed for the more cluttered stereoenriched (αβ)-isomers, which was also concomitant with a smaller population of inner sphere complex. In contrast, the stereoisomers mixture led to a strong decrease of Pu extraction because of an antagonistic association in the mixed complexes.