Physicochemical Properties/Descriptors Governing the Solubility and Partitioning of Chemicals in Water–Solvent–Gas Systems. Vapor Pressure and Concentration of Chemicals Above Saturated Aqueous Solutions

Abstract

AbstractVapor Pressure (VP) and concentration of chemicals above saturated aqueous solutions (Cair), interconnected by Henry's law, are important properties with significant effects on the transport and partitioning of chemicals among environmental compartments. Therefore, it is desirable to be able to calculate them from the chemical structure. Published data of 460 diverse chemicals (29 gases at 298 K, 368 liquids, 63 solids) on VP, solubility in water (Sw), partitioning of chemicals in the system water–air (gas) (Lwg) were used to construct QSPRs for VP and Cair on the basis of HYBOT physicochemical descriptors. The correlations of log VP and log Cair in the framework of the usual regression model provided unsatisfactory results but helped to recognize the main factors influencing the investigated properties: the volume‐related term expressed by the molecular polarizability α, H‐bond acceptor factor (ΣCa), and H‐bond donor factor (ΣCd). They all, not unexpectedly, contribute negatively to log VP and log Cair. An alternative approach based on combination of the similarity concept and a regression model with the same physicochemical descriptors essentially improved statistics. Using nearest neighbors (structurally related compounds with high Tanimoto similarity coefficient) and simultaneously aiming at small differences in α, ΣCa, and ΣCd as compared with corresponding data of compounds‐of‐interest the results of prediction of VP and Cair were excellent with standard deviations close to the error of experimental determination for liquid and solid chemicals.