General solvation equation

The retention depends on the nature of both the stationary phase and the organic modifier in the mobile phase. Therefore CHI values obtained using different systems show different sensitivities towards solute characteristics. This has been studied systematically and used for the quantitative calculation of solute molecular descriptors (H-bond donor capacity, H-bond acceptor capacity and dipolarity/polarizability) for application in a general solvation equation [21]. 

One of the most comprehensive hydrogen-bonding scales is due to Abraham and his coworkers50, who have derived the general solvation equation 651... 

Abraham et al. [2] published a number of papers in which they analyzed Young s data set using MLR and gave a general solvation equation in which various solvent-solute interactions were described by solute descriptors and equation coefficients (Eq. 16)... 

Several computational methods require the user to input experimental parameters in order to make predictions. Examples include Yalkowsky s general solvation equation [18], which requires melting points, and Abraham s method [19], which requires five experimentally derived parameters. These methods are not useful for cases before the compounds are synthesized (e.g., in library design or virtual screening), and so they will not be considered further here. 

This is because the definition of Eq. 4.21 seems not to apply in this case. Thus, for methane, with log Pcydohex. = 1-33 and VM = 30.3 cm3, the log BB value calculated by Eq. 4.20 is 1.62 log units but the real value is only 0.04 log units [26], Therefore, the authors attempted to evaluate systematically those factors influencing the distribution of solutes between blood and brain, starting with their general solvation equation ... 

Equation (3.42), the general solvation equation, can also be used to predict the partition coefficient ... 

Similar to the blood-brain barrier distribution there is a large number of biochemical and toxicological proces.ses that involve aqueous solutes interacting with a given system. In principle, the general solvation equation. Eiq. (12.14), could be applied to any such... 

THE NORMALISED REGRESSION COEFFICIENTS OF THE GENERAL SOLVATION EQUATION OBTAINED FOR THE INVESTIGATED HPLC SYSTEMS... 

THE CX3EFFICIENTS OF THE GENERAL SOLVATION EQUATION, EQ. (12.14). OBTAINED FOR SELECTED DIVERSE CHROMATOGRAPHIC STATIONARY PHASES... 

With the application of the fast gradient CHI values it takes approximately six times five minutes to determine the basic molecular properties of newly synthesised drug molecules. The method can be fully automated, and small impurities can be separated during the HPLC run so that they do not disturb the measurements. Very small quantities of compounds are used for these measurements, and we believe that this method will help design soluble drug molecules with the desired absorption, and brain penetration, etc., by using the general solvation equations already known for these systems. 

Abraham and coworkers have developed a general solvation equation... 

Abraham developed what is termed a general solvation equation. The main idea behind the model involves the creation of a cavity in the solvent, incorporation of the solvent in the cavity, and turning on solute-solvent interactions. These interactions require a relevant solute parameter, and the ones chosen were the excess molar refraction, ttf the solute dipolarity/polarizability, flf and Pf the hydrogen-bond acidity and basicity, respectively, and a characteristic volume. Applying this general equation to 132 solutes in aqueous SDS, Abraham et al. obtained the following equation for the partition coefQcient ... 

Quina et al. have used the same general solvation equation on solubilizates in SDS, Cj2Br, CigBr, and the nonionic Brij-35 surfactant. In SDS they do not attempt to fit as many solubilizates as Abraham et al., using 66 solubilzates for SDS, 39 for Ci2Br, and 42 for C,gBr. The equations read... 

The second aspect is more fundamental. It is related to the very nature of chemistry (quantum chemistry is physics). Chemistry deals with fuzzy objects, like solvent or substituent effects, that are of paramount importance in tautomerism. These effects can be modeled using LFER (Linear Free Energy Relationships), like the famous Hammett and Taft equations, with considerable success. Quantum calculations apply to individual molecules and perturbations remain relatively difficult to consider (an exception is general solvation using an Onsager-type approach). However, preliminary attempts have been made to treat families of compounds in a variational way [81AQ(C)105]. 

Yang G, Ran Y and Yalkowsky SH. Prediction of the aqueous solubility comparison of the general solubility equation and the method using an amended solvation energy relationship. J Pharm Sci 2002 91 517-33. 

Kamlet M. J., Abboud J.-L., Abraham M. H. and Taft R. W. (1983) Linear Solvation Energy Relationships. 23. A Comprehensive Collection of the Solvatochromic Parameters, 7i, a, and ft, and Some Methods for Simplifying the Generalized Solvatochromic Equation, J. Org. Chem. 48, 2877-2887. 

Kamlet MJ, Abboud JLM, Abraham MH, Taft RW (1983) Linear solvation energy relationships. 23. A comprehensive collection of the solvatochromic parameters, jr, a, and /3, and some methods for simplifying the generalized solvatochromic equation. J Org Chem 48 2877-2887. 

The starting point is the well-known generalized Langevin equation (GLE) as adopted for stochastic motions involving coupling to a solvent coordinate. We employ the notation of Hynes [63] which is consistent with the discussion of solvation in Section II. 

In a recent approach that was successfully tested for small hydrocarbons the solvation was treated semi-analytically as a statistical continuum[167]. The method treats the sum of the solvent-solvent cavity (Gcav) and the solute-solvent van der Waals (Gvdw) terms by determining the solvent accessible surface1-1681, and the solute-solvent electrostatic polarisation term (Ges) is calculated by a modified version of the generalized Bom equation[ 167,16 ]. 

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