Partition and transfer of chlorophenoxy acids (herbicides) in water–non-aqueous media

Abstract

The distribution of various chlorinated compounds, 2,4-dichlorophenoxyethanoic acid, 2,4-D, 2-(2,4-dichlorophenoxy)propionic acid, 2,4-DP, 2,4,5-trichlorophenoxyethanoic acid, 2,4,5-T, 2-(2,4,5-trichlorophenoxy)propionic acid, 2,4,5-TP and 2,3,6-trichlorophenylethanoic acid, 2,3,6-T, was investigated in mutually saturated water–non-aqueous solvent systems at 298.15 K. The data were used to calculate (i) the distribution constant, K_d, referred to the process involving ionic species in the aqueous phase and undissociated species in the organic phase and (ii) the dimerisation constant, K_dim, in aprotic media saturated with water. A new treatment used to derive these data is described. The K_d values in the mutually saturated solvents for the various pesticides are compared with corresponding data in the pure solvents derived from solubility measurements in water and in non-aqueous solvents. Data in water were corrected for ion-pair formation while those in the organic phase were corrected for dimerisation. Good agreement is found between the two sets of data.