THE EFFECT OF STERIC HINDRANCE OF THE AMIDIC SUBSTITUENTS OF THE CARBAMOYLMETHYLPHOSPHINE OXIDES ON 3RD PHASE FORMATION

Increasing the steric hindrance of the substituents on the amidic nitr ogen of the carbamoylmethylphosphine oxide class of extractants leads to a significant decrease in the tendency of these compounds to form a third phase during the extraction of nitric acid. An increase in ster ic hindrance leads to a reduction in the accessibility of the nitrogen and in the dipole-dipole and dipole-induced-dipole attractions betwee n extractant molecules, thereby reducing the tendency to form a third phase. A corresponding increase in the amount of uranium that could be extracted without third phase formation was not observed due to a red uction in the interaction of the extractant with the diluent because o f coordination with the metal ion by both polar groups.