Linear solvation energy relationship related compounds

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 ... 

A linear solvation energy relationship (LSER) study of tautomerism in aromatic Schiff bases and related azo compounds indicates that the aminoenone tautomer is always the more polar, and is specifically favoured by proton donor solvents (binding to the second lone pair of the carbonyl). Effects of aromatization and benzo fusion are also discussed.26... 

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. 

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]. 

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