CORRELATION ANALYSIS IN STRUCTURE AND REACTIVITY STUDIES OF MONO-BASIC PHOSPHORUS ESTERS IN RARE EARTH EXTRACTION

A series of substituent constants for steric effect E_(PA)~(RE) was estimated for the structure and reac- tivity studies of monobasic phosphorus esters in rare earth extraction based on the general conception suggested by us that the extraction behaviours of a ligand are determined chiefly by the polar and steric effects of the substituents, while the σ~p was proposed as an empirical structure parameter for the polarity. A good result in correlation analysis was obtained when using these parameters in different extraction systems. The E_(PA)~(RE) is, however, correlated linearly with Charton's υ. The summation of polar and steric effects in an extractant can be evaluated by using additivity rule. The calculated extraction equilibrium constant was in good agreement with the experimental data. These constants have given the important structural information in the molecular design of new extractants.