Molecular interactions induction coefficients

Lipophilicity is a molecular property experimentally determined as the logarithm of the partition coefficient (log P) of a solute between two non-miscible solvent phases, typically n-octanol and water. An experimental log P is valid for only a single chemical species, while a mixture of chemical species is defined by a distribution, log D. Because log P is a ratio of two concentrations at saturation, it is essentially the net result of all intermolecular forces between a solute and the two phases into which it partitions (1) and is generally pH-dependent. According to Testa et al. (1) lipophilicity can be represented (Fig. 1) as the difference between the hydrophobicity, which accounts for hydrophobic interactions, and dispersion forces and polarity, which account for hydrogen bonds, orientation, and induction forces ... 

Expression [8.62] has several merits, but also several defects. Among the latter we note that given powers of R may collect terms of different origin. For example, the term R" describes both the induction dipole-induced dipole interaction and the dispersion dipole-di-pole interaction two contributions with a different sensitivity with respect to changes in the molecular system. Theory and computational methods both permit getting two separate C coefficients for the two contributions. This is done in a limited number of potentials (the most important cases are the NEMOn and the ASP-Wn families of models). The most popular choice of a unique term for contributions of different origin is motivated by the need of reducing computational efforts, both in the derivation and in the use of the potential. To fit a unique coefficient means to use AE values only for two coefficients there is the... 

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