Physicochemical properties/descriptors governing the solubility and partitioning of chemicals in water-solvent-gas systems. Part 1. Partitioning between octanol and air

Abstract

QSPR analyses of a data set containing experimental partition coefficients in the three systems octanol-water, water-gas, and octanol-gas for 98 chemicals have shown that it is possible to calculate any partition coefficient in the system ‘gas phase/octanol/water’ by three different approaches: (1) from experimental partition coefficients obtained in the corresponding two other subsystems. However, in many cases these data may not be available. Therefore, a solution may be approached (2), a traditional QSPR analysis based on e.g. HYBOT descriptors (hydrogen bond acceptor and donor factors, ΣCa and ΣCd, together with polarisability α, a steric bulk effect descriptor) and supplemented with substructural indicator variables. (3) A very promising approach which is a combination of the similarity concept and QSPR based on HYBOT descriptors. In this approach observed partition coefficients of structurally nearest neighbours of a compound-of-interest are used. In addition, contributions arising from differences in α, ΣCa, and ΣCd values between the compound-of-interest and its nearest neighbour(s), respectively, are considered. In this investigation highly significant relationships were obtained by approaches (1) and (3) for the octanol/gas phase partition coefficient (log L _og).

Keywords:

• Partition
• Gas-octanol-water
• H-bond factors
• Molecular polarisability
• Similarity

Acknowledgements

This investigation was supported by the International Science & Technology Center (Project # 888). O. A. R. would like to thank the Research Center Borstel (Germany) for a two months stipend in 2005.

Notes

∗Email: [email protected]

Additional information

Notes on contributors

K.-J. Schaper∗

∗Email: [email protected]