Free energy of transfer between

For two relatively immiscible solvents log P can be considered [1] proportional to the molar Gibbs free energy of transfer between octanol and water ... 

The partition coefficient KmK is directly related to the free energy of transfer between the aqueous and the membrane phase. The enthalpy and entropy contri-... 

Fig. 2.11. Correlation between accessible surface area and hydrophobicity expressed as free energy of transfer between organic solvent and water for various hydrocarbons (iunlabeled dots), and for amino acids. The accessible surface area is obtained by rolling a water molecule (sphere 1.4 A) around the solute molecule and calculating the contact surface. The slopes of the lines are 25 cal A-2 for hydrocarbons and polar amino acids and 22 cal A-2 for nonpolar amino acids [137]...

The free energy of transfer between the solvent mixture (xa) and pure solvent A is calculated using Eqs. (24) to (26) ... 

Table 2. Cumulative constants of ion solvation equilibria and free energies of transfer between solvent A and solvent... 

In the first part of this review we have briefly presented several redox systems which have both Ox and Red components only weakly interacting with the solvents, while their free energy of transfer between various solvents was assumed to be equal to zero. 

The heart of liquid chromatography lies in the highly selective chemical interactions that occur in both the mobile and stationary phases. It is now possible to rapidly separate compounds whose difference in free energy of transfer between the mobile and stationary phases is only a few calories per mole. Columns exhibiting virtually every type of possible selectivity exist—from shape selectivity to charge selectivity to size selectivity to enantio-selectivity. It is also possible to generate additional selectivity through clever manipulations of the mobile phase additives that interact with the solute in the mobile phase can create unique selec-tivities in columns that do not show that type of selectivity. 

The same approach can be extended to reactions between two ions. The expression for the free energy of transfer of ions of charge Z and zb from infinite separation to the reaction distance is... 

While the PM3-SM4 model does appear to slightly underestimate the polarity of the enol component, there is some cancellation of errors upon considering the differential transfer free energies between cyclohexane and water. As noted above, experiment indicates that the differential free energy of transfer of the dione and the enol is 3.1 kcal/mol the PM3-SM4 model predicts this value to be 2.8 kcal/mol, in excellent quantitative agreement. AM1-SM4 is less satisfactory in this regard, predicting only 1.9 kcal/mol. 

As may be inferred from Table 2, the free energies of transfer observed for carrier antibiotics lie between — 1 and — 8 kcal mole-1 s) and are... 

Assuming again that y follows the Debye-Hiickel law, the total pressure P is measured as a function of the solute concentration, then the vapor phase y, the only unknown in Equation 4, can be calculated, and hence the activities a and a2 can also be calculated, provided the activities ai° and a of each solvent prior to the addition of the solute are known dG°/dZ can be obtained next from Equation 1. Finally, integration of dG°/<9Zi with respect to Z leads to the standard molar free energy of transfer AG°t between Z = 1 (if water is chosen as the reference solvent) and any value of Z. ... 

In this case, the free energy of transfer of i from the pure liquid to an ideal gas phase (i.e., air) AaLG and thus the corresponding gas (air)-liquid equilibrium partition constant, Ki lL (see Eq. 3-16 below), are direct measures of the attractive forces between like molecules in the liquid (recall we assume no interactions among gas phase molecules). Note that for the following discussion we use a subscript a (air) to denote the ideal gas phase. Furthermore a capital L is used to describe the pure liquid in order to distinguish from other liquid phases (subscript ). Finally, the superscript indicates that we are dealing with a property of a pure compound. 

To illustrate, we first consider a simple one-parameter LFER approach that is very widely used and, unfortunately, often also abused in environmental organic chemistry. In this approach, a linear relationship is assumed between the free energies of transfer of a series of compounds in two different two-phase systems ... 

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