Solutions linear solvation energy relationship

Kamlet-Taft Linear Solvation Energy Relationships. Most recent works on LSERs are based on a powerfiil predictive model, known as the Kamlet-Taft model (257), which has provided a framework for numerous studies into specific molecular thermodynamic properties of solvent—solute systems. This model is based on an equation having three conceptually expHcit terms (258). 

Kamlet, M. J., Doherty, R. M., Carr, P., Abraham, M. H., Marcus, Y Taft, R. W. Linear solvation energy relationships. 46. An improved equation for correlation and prediction of octanol-water partition coefficients of organic non-electrolytes (including strong hydrogen bond donor solutes)./. Phys. Chem. 1988, 92, 5244-5255. 

Logarithmic bioconcentration factors have been shown to be correlated with the logarithmic octa-nol/water partition coefficient in aquatic organisms (Davies and Dobbs, 1984 de Wolf et al., 1992 Isnard and Lambert, 1988) and fish (Davies and Dobbs, 1984 Kenaga, 1980 Isnard and Lambert, 1988 Neely et al., 1974 Ogata et al., 1984 Oliver and Niimi, 1985). In addition, bioconcentration factors are well correlated by a linear solvation energy relationship (coimnonly known as LSER) that includes the intrinsic solute molecular volume and solvatochromic parameters that measnre hydrogen bond acceptor basicity and donor acidity of the componnd (Park and Cho, 1993). 

Kamlet, M.J., Doherty, R.M., Abraham, M.H., Carr, P.W., Doherty, R.E., and Taft, R.W. Linear solvation energy relationships. 41. Important differences between aqueous solubility relationships for aliphatic and aromatic solutes, J. Phys. Chem., 91(7) 1996-2004, 1987. 

The LFER, which is also known as the linear solvation-energy relationship (LSER), was developed by Taft et al. (62) and established by Abraham and coworkers (63). The LFER has been used for characterization of two-phase partitioning processes of solutes such as octanol-water and chromatographic processes such as HPLC, GLC, and TLC. The general equation is expressed as follows ... 

A linear solvation energy relationship (LSER) has been developed to predict the water-supercritical CO2 partition coefficients for a published collection of data. The independent variables in the model are empirically determined descriptors of the solute and solvent molecules. The LSER approach provides an average absolute relative deviation of 22% in the prediction of the water-supercritical CO2 partition coefficients for the six solutes considered. Results suggest that other types of equilibrium processes in supercritical fluids may be modeled using a LSER approach (Lagalante and Bruno, 1998). 

Since solvatochromic parameters are derived from direct measurements of the energy resulting from intermolecular interaction, they can be used to predict solubility, which is determined by solute-solute, solvent-solvent, and solute-solvent interaction energies. For nonself-associated liquid aliphatic compounds with a weak or nonhydrogen-bond donor (Taft etal., 1985 Kamlet etal., 1986), the solubility in water at 29S was related to molar volunWjf, hydrogen-bond basicity j and polarity/polarizability (jf) by a linear solvation energy relationship (LSER) as in Equation 3.55 ... 

Kamlet, M., R.M. Doherty, M.H. Abraham, Y. Marcus, and R.W. Taft. 1988. Linear Solvation Energy Relationships. 46. An Improved Equation for Correlation and Prediction of Octanol/Water Partition Coefficients of Organic Nonelectrolytes. (Including Strong Hydrogen Bond Donor Solutes). J. Phys. Chem. 92, 5244-5255. 

It has been established (Kamlet and Taft 1985) that a large number of solvent effects involving a given solute and a series of solvents can be described by the general linear solvation energy relationship (LSER) ... 

The Kamlet-Taft u polarity/polarizability scale is based on a linear solvation energy relationship between the n it transition energy of the solute and the solvent polarity ( 1). The Onsager reaction field theory (11) is applicable to this type of relationship for nonpolar solvents, and successful correlations have previously been demonstrated using conventional liquid solvents ( 7 ). The Onsager theory attempts to describe the interactions between a polar solute molecule and the polarizable solvent in the cybotatic region. The theory predicts that the stabilization of the solute should be proportional to the polarizability of the solvent, which can be estimated from the index of refraction. Since carbon dioxide is a nonpolar fluid it would be expected that a linear relationship... 

Many biochemical and toxicological properties of compounds Xt depend on solute-solvent interaction can be rationalized in terms of the linear solvation-energy relationship (LSER) (Kamlet et ah, 1981) ... 

The standard molar Gibbs energy of solvation can also be derived from pure component data using spectroscopic information for determining solvatochromic parameters in respect of activity, basicity, polarity, etc. There exists a number of linear solvatochromic scales, the most widely used of which is the linear solvation energy relationship (LSER) devised by Kamlet and Taft [37, 38]. The Nernst distribution of solute i according to Kamlet is ... 

Another important treatment of multiple interacting solvent effects, in principle analogous to Eq. (7-50) but more precisely elaborated and more generally applicable, has been proposed by Kamlet, Abboud, and Taft (KAT) [84a, 224, 226], Theirs and Koppel and Palm s approaches have much in common, i.e. that it is necessary to consider non-specific and specific solute/solvent interactions separately, and that the latter should be subdivided into solvent Lewis-acidity interactions (HBA solute/HBD solvent) and solvent Lewis-basicity interactions (HBD solute/HBA solvent). Using the solvato-chromic solvent parameters a, and n, which have already been introduced in Section 7.4 cf. Table 7-4), the multiparameter equation (7-53) has been proposed for use in so-called linear solvation energy relationships (LSER). 

The multiparameter equation (7-54) seems to be rather difficult to apply. However, in practice, most of the linear solvation energy relationships that have been reported are simpler than indicated by Eq. (7-54) since one or more terms are inappropriate. For example, if the solute property A does not involve the creation of a cavity or a change in cavity volume between initial and activated or excited states (as is the case for solvent effects on spectral properties), the term is dropped from Eq. (7-54). If the solvent-dependent process under study has been carried out in non-HBD solvents only, the a term drops out. On the other hand, if the solutes are not hydrogen-bond donors or Lewis acids, the P term drops out of Eq. (7-54). Thus, for many solvent-dependent processes, Eq. (7-54) can be reduced to a more manageable one-, two- or three-parameter correlation equation by a judicious choice of solutes and solvents [226],... 

Electric polarization, dipole moments and other related physical quantities, such as multipole moments and polarizabilities, constitute another group of both local and molecular descriptors, which can be defined either in terms of classical physics or quantum mechanics. They encode information about the charge distribution in molecules [Bbttcher et al, 1973]. They are particularly important in modelling solvation properties of compounds which depend on solute/solvent interactions and in fact are frequently used to represent the -> dipolarity/polarizability term in - linear solvation energy relationships. Moreover, they can be used to model the polar interactions which contribute to the determination of the -> lipophilicity of compounds. 

Linear solvation energy relationships constitute the basis on which effects of solvent-solute interactions on physico-chemical properties and reactivity parameters are studied. In general, a property <)> of a species A in a solvent S can be expressed as ... 

The underlying philosophy of the linear solvation energy relationships is based on the possibility of studying these two functions, after a proper choice of the reference systems and properties. Moreover, it has been recognized that solution properties c ) mainly depend on three factors a cavity term, a polar term, and hydrogen-bond term ... 

Two other general linear solvation energy relationships for solute physico-chemical properties in a fixed phase [Abraham et al, 1990b Abraham et al, 1991a Abraham et al, 1991b Abraham, 1993b Abraham et al, 1994a] are ... 

This term is a measure of the exoergic balance (i.e. release of energy) of solute-solvent and solute-solute dipolarity / polarizability interactions. This term, denoted by n, describes the ability of the compound to stabilize a neighbouring charge or dipole by virtue of nonspecific dielectric interactions and is in general given by -> electric polarization descriptors such as -> dipole moment or other empirical - polarity / polarizability descriptors [Abraham et al, 1988]. Other specific polarity parameters empirically derived for linear solvation energy relationships are reported below. 

QSAR method based on the philosophy of the -> Linear Solvation Energy Relationships, whose empirically derived molecular descriptors are substituted hy descriptors defined in the framework of - computational chemistry [Famini et ai, 1991 Famini et ai, 1992 Famini and Wilson, 1994a]. The TLSER descriptors were developed with the aim of optimally correlating with LSER descriptors, thereby being as generally applicable to solute/solvent interactions as are the LSER descriptors. 

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