SAR/QSAR approaches to solubility, partitioning and sorption of phthalates

The environmental behavior of xenobiotics such as phthalates is closely con nected to parameters such as are solubility (C-w(sat)), partitioning (e.g. K-ow) and sorption (e.g. K-oc). In this paper the solubility, octanol-water partitioning and sorption of a series of phthalic acid esters are describe d through various SAR/QSAR concepts including molecular connectivity indice s (MCI), electrotopological atomic state indices (EASI) and group-contribut ion (UNIFAC). Advantages and disadvantages of MCI and UNIFAC based QSAR's f or phthalates are discussed. The water solubility as well as the octanol - water partitioning are satisfactorily calculated by application of UNIFAC-d erived activity coefficients. Octanol-water partitioning and sorption, but to a lesser extent solubility are, according to MCI analyses, well correlat ed to molecular size. Octanol-water partitioning and sorption, but to a les ser extent solubility are, according to EASI analyses, well correlated to h ydrophobicity as expressed by the "alkyl- group" electrotopological index. The latter correlations is further improved by introducing the polar compon ent as expressed by the "ester- group" electrotopological index. (C) 1999 E lsevier Science Ltd. All rights reserved.