Effect of anomalous aryl strengthening in the series of N-phosphorylureas

Within the series of model N-diorganophosphoryl-N'-n-octylureas, the ability to extract uranium(VI) from nitric acid solutions is maximal for N-diphenylphosphoryl derivative and sharply decreases when phenyl groups are replaced with n-alkyl or cycloalkyl substituents; this indicates the presence of ‘anomalous aryl strengthening’ effect also in the series of N-phosphorylureas, a new promising class of organophosphorus extractants.