The transfer of neutral molecules, ions and ionic species from water to wet octanol

Abstract

Partition coefficients for transfer from water to wet octanol have been set out for permanent ions, and for ionic species derived from neutral molecules by loss or acceptance of a proton. A previous equation for the partition of neutral compounds from water to wet octanol has been extended to include the partition of permanent ions, and ionic species; the only additional descriptors required are J(+) for cations and J(-) for anions. Fourteen cations and twelve anions are included in the equation. It is shown that differences in partition coefficients between neutral species and the corresponding ionic species, as log P(oct), are not at all constant. For carboxylic acids and the corresponding anion, differences are about 5.0 log units, for phenols and the corresponding anion differences range from 2.2 to 4.9 log units, and for amines and the corresponding protonated cations there is an enormous range of differences from 0.6 to 7.1 log units.

The transfer of neutral molecules, ions and ionic species from water to benzonitrile; comparison with nitrobenzene

“…We obtained a value for log P(H + ) that gave self-consistent values for log P for the protonated pyridine-Noxides and log P for the various cations. Details of the observed and calculated single-ion log P values are in Table 3; the descriptors for the ions are as before [6][7][8][9][10]. Table 3.…”

“…Table 1 [6][7][8][9][10], and descriptors for a number ions and ionic species are in Table 2. In the present context, it is of some interest that we were not able to characterize the solvent nitrobenzene completely and could not obtain the j + coefficient for anions.…”

The hydrogen bond acidity and other descriptors for oximes

“…Then eqn (7) can be applied provided that log K w as obtained for pure water is the same for water saturated with octanol. There is a considerable amount of experimental evidence that log K w is indeed the same, within any realistic experimental error, for water and octanol saturated water, 20 and so eqn (7) can be applied to wet octanol as well as to solvents that take up only very small quantities of water.…”

Aplicação do conceito do par iônico e seus efeitos sobre a lipofilicidade de brometos de amônio quaternários estruturalmente análogos a procaína, com atividade de bloqueio da transmissão neuromuscular, para estudos de <i>(Q)SAR</i>

“…Esta pode ser aplicada no estudo da partição de diversos compostos neutros (não ionizáveis), de diferentes classes químicas (Abraham & Acree Jr, 2010). 0,088 + 0,562E -1,054S + 0,034A -3,460B + 3,814V (Equação 1.8) n = 613, R² = 0,995, s = 0,116, F = 23162 A aplicação da equação solvatocrômica para a partição, por ser tratar de uma relação linear de energia livre, pode ser útil para a compreensão de outros processos relacionados, que envolvem a transferência de um composto entre duas fases como, por exemplo, a permeação entre membranas ou tecidos biológicos (barreira hematoencefálica) e, a distribuição entre solo-água (de interesse ambiental) (Quina et al, 1995;Poole et al, 2013;Balaz, 2015).…”

“…A Figura 1.5 apresenta os equilíbrios envolvidos na partição de um composto permanentemente carregado (M + ), em presença de um contraíon de carga oposta (X -), na qual se observa a possibilidade de partição com formação de par iônico entre M + e X -, bem como de partição sem formação de par iônico, ou seja, M + e Xcomo um par de íons separados (Abraham & Acree Jr, 2010).…”