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, SigmaCa and SigmaCd, together with polarisability alpha, 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 alpha, SigmaCa, and SigmaCd 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 Log).

Sublimation of Molecular Crystals: Prediction of Sublimation Functions on the Basis of HYBOT Physicochemical Descriptors and Structural Clusterization

“…It can be formulated by the expression: 0.5 ≤ T c ≤ 1. In order to calculate the unknown thermodynamic function within the clusters, we applied an approach based on similarity and physicochemical descriptors introduced by Raevsly et al According to this approach, any thermodynamic function, Y (i) (where Y = Δ G sub 298 , Δ H sub 298 , Δ S sub 298 ), is calculated on the basis of experimental values of the same function of structurally closely related compounds (nearest neighbors, nn), Y (nn) , and the difference in their relevant physicochemical descriptors, Δ Y : normalY false( normali false) = Y false( nn false) + normalΔ Y If we knew the thermodynamic function of the nearest neighbor and the correlation equation describing the relationship between the thermodynamic function and physicochemical descriptors obtained on the basis of the training set (for example, eq ), then the value of the unknown thermodynamic function was estimated by the following equation: Y ( i ) = Y ( nn ) + A 1 ( α ( i ) − α ( nn ) ) + A 2 ( Σ C a ( i ) − Σ C a ( nn ) ) + A 3 ( Σ C d ( i ) − …”

“…It can be formulated by the expression: 0.5 e T c e 1. In order to calculate the unknown thermodynamic function within the clusters, we applied an approach based on similarity and physicochemical descriptors introduced by Raevsly et al 31 According to this approach, any thermodynamic function,…”

“…Second, for each class of the compounds it is necessary to normalize the pair potential functions. In this work, we would like to propose the QSAR approach for estimation of sublimation thermodynamic functions based on both the HYBOT descriptors and the conception of the nearest neighbors. − The approach gives an opportunity to predict the above-mentioned thermodynamic functions of various molecular crystals only by their chemical structures. It should be noted that if the experimental data volume growth persists the proposed calculation algorithms will work more effectively.…”

Unified Physicochemical QSPR Model of the Partitioning and Solubility of Chemicals in the Triple System “Water–Octanol–Air”

“…9 predicts that all three physicochemical properties contribute negatively to P air,o ¼ C air /C o , or in other words, with increasing a, SC a , and j SC d j the interaction with octanol and, thus, the concentration in octanol increases. Using the same descriptors, we recently obtained a corresponding QSPR model by direct correlation with observed log P air,o data of 98 compounds with one functional group [14]:…”

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

“…In previous publications, we presented QSPR models based on similarity and HYBOT (hydrogen bond thermodynamics) descriptors for the systems octanol -water (log K ow data of $ 11 000 compounds) [1 -3], water -air (n ¼ 530 compounds) [4], solubility in water (787 liquids and $ 2000 solids) [5 -7], octanol -air (n ¼ 98) [8], and solubility in octanol (n ¼ 218) [9].…”