Collander relation

Numerous examples available from the application of the octanol-water system allow translation between different solvents or the modeling of a lipid membrane, provided the Collander relation [19] is valid. 

Collander, R. The partition of organic compounds between higher alcohols and water, Acta Chem. Scand., 5 774-780,1951. Collett, A.R. and Johnston, J. Solubility relations of isomeric organic compounds. VI. Solubility of the nitroanilines in various liquids, J. Phys. Chem., 30(l) 70-82, 1926. 

Thus, for the ir constants for the same molecular system RX depends linearly on the solvent systems in which they were determined. Since ir is an additive-constitutive property of the molecule we can obtain logP from the ir values of the constituting parts (23, 24). The linear relation between logP values for the same compound in different solvents should also hold. This is reflected in the linear relation between partition coefficients in different solvent systems as expressed by Collander (111)... 

The analysis of the parameters representing the effect of the medium in terms of extrathermodynamical relations has shown (see above, section A.2) that the hydrophobic substituent constant it depends on the molecules from which it is derived. For example, hydrophobic constants derived from the octanol/water partition coefficients of aromatic molecules differ from those obtained from aliphatic molecules (112). Collander s equation (111) provides the empirical basis for the evaluation of logP values for the same molecule in different solvents. However, solvents with markedly different solvation properties (e.g., hydrogen bonding ability) do not conform to Collander s equation (see below, section C.3). 

In the case of parameters related to the effects of the medium Collander s relation (equation 42) has been shown to hold for many different compounds in many solvent systems (112-118). For example, partition coefficients between water and oleyl alcohol, isobutyl alcohol, and xylene correlate well with partition... 

The use of a single standard system for drug partitioning is justified by the Collander equation (eq. 20) [183], which relates partition coefficients from different solvent systems. 

Fig. 1. Permeability of Nitella cell membranes to non-electrolytes in relation to the olive oil solubility of these solutes. On the ordinate the logarithm of the permeability (in units of 10 cm/sec) on the abscissa, the logarithm of the olive oil/water partition coefficient of the permeant. Data measured at 20°C. Crosses molecular weight up to 50 open circles molecular weights from 60 to 119 filled circles molecular weights above 120. Data taken from Collander [3]. The straight line is of unit slope.

Fig. 7. Relation between ether/water partition coefficient (abscissa) and Iscbutanol/water partition coefficient (ordinate) for a large number of non-electrolytes. Figure taken with kind permission from Collander [18].

Collander [51] determined the distribution coefficieiits of 50 organic solutes in five different solvent systems. He noted that for a given solute, the distribution coefficient in one solvent system (ui) was related to that in another (02) by Equation (41). a and b are constants characteristic of the two solvent systems. 

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