Equations for the Partition of Neutral Molecules, Ions and Ionic Species from Water to Water–Ethanol Mixtures

Abstract

Equations set up for the transfer of neutral solutes from water to water-ethanol mixtures can also be used to correlate the transfer of ions and ionic species, as log 10 P , where P is the partition coefficient. Only two additional terms are required in the equations, one for anions and one for cations. The extended equations can fit log 10 P values for anions and cations with a standard deviation of about 0.2 to 0.3 log units for transfer of 41 anions and cations from water to various water-ethanol mixtures from 10 % ethanol to 100 % ethanol by volume. The log 10 P values for carboxylate anions and protonated amine cations as obtained from the variation of pK a with solvent are quite compatible with log 10 P values for simple anions and cations.

Analysis of the solubility of betaine: calculation of descriptors and physicochemical properties

“…(3), and these are given in Table 3. The various equations refer to the partition between water and the dry solvent [16][17][18][19][20] or between water and a water-ethanol mixture [23,24]. Although such partitions are hypothetical, the corresponding equations are extremely useful in the analysis of solubilities [11].…”

Descriptors for ions and ion-pairs for use in linear free energy relationships

“…The coefficients c, e, s, a, b and v are the same as those for the equation for neutral compounds. Equations for the partition of neutral compounds from water to various water-ethanol mixtures have been determined by Abraham and Acree [64] and they were later able to obtain enough log P values for ions and ionic species to obtain the coefficients for the ionic equations in Table 5 [65].…”

“…[65] Ref. [67] Cl As mentioned in the introduction, there has been considerable work on the extension of the Abraham equation for neutral species in connection with HPLC retention, although not in terms of Eq.…”

“…Very peculiarly, wet octanol has a dielectric constant, ε = 8.85, less than that of dry octanol, ε = 10.25, and so K ass is larger than expected. Abraham and Acree [65] estimated K ass for electrolytes in wet octanol as 100 × K ass in propan-1-ol and were then able to predict values of log P for transfer from water to wet octanol of ion-pairs not used to set up Eq. (61).…”

Abraham model correlations for describing solute transfer into anhydrous 1,2-propylene glycol for neutral and ionic species

“…[5][6][7][8] The Abraham model is based on two linear free energy relationships (LFERs), [9,10] the first equation describing the transfer of neutral molecules and ionic species between two condensed phases:…”