Aliphatic hydrocarbons partition coefficient

FIGURE 2.2.6 Octanol -water partition coefficient versus Le Bas molar volume for aliphatic and cyclic hydrocarbons. 

Partition coefficients of a series of aliphatic hydrocarbons, including n-hexane, have been determined in human tissues (Perbellini et al. 1985). The following partition coefficients for n-hexane (olive oil/air, blood/air, tissue/air) were determined olive oil, 146 blood, 0.80 liver, 5.2 kidney, 3 brain, 5 fat, 104 muscle, 5 heart, 2.8 and lung, 1. Saline/air partition was not reported separately for n-hexane, but was very low for the range reported for the entire group of compounds (0.1-0.4). 

Coates M, Connell DW, Barron DM. 1985. Aqueous solubility and octanol to water partition coefficients of aliphatic hydrocarbons. Environ Sci Technol 19 628-632. 

Perbellini L, Brugnone F, Caretta D, et al. 1985. Partition coefficients of some industrial aliphatic hydrocarbons (C5-C7) in blood and human tissues. Br J Ind Med. 42(3) 162-167. 

Estimation of this parameter for aliphatic hydrocarbons are lacking in the documented literature Octanol/water partition coefficient, log Ko ... 

Coates, M., D. W. Connell, and D. M. Barron, Aqueous Solubility and Octan-l-ol to Water Partition Coefficients of Aliphatic Hydrocarbons. Environ. Sci. Technol., 1985 19, 628-632. 

FIGURE 5.2.10 Octanol-water partition coefficient versus molar solubility (liquid or supercooled liquid) for halogenated aliphatic hydrocarbons. 

Materials that are solubilized in polyethylene glycol can be solubilized in the polyoxyethylene chains on the surface of a nonionic micelle. Ismail, Gouda, and Motawi found that the micellar partition coefficients of barbiturates in polysorbates 20, 40, 60, and 80 is a function of the solute substituents and is proportional to the octanol-water partition coefficient of the barbiturate. Similarly, Ikeda, Kato, and Tukamoto showed that the solubilization of alkyl barbiturates by polyoxyethylene lauryl ether is not dependent upon the number of carbons in the substituents. Since the different polysorbates contain different aliphatic groups, the rather small dependence of solubilization upon polysorbate number (i.e., upon alkyl chain length) suggests that the barbiturates are not solubilized primarily in the hydrocarbon portion of the micelle. Gouda, Ismail, and Motawi showed that the solubilization of barbiturates in polyoxyethylene stearates is proportional to the number of polyoxyethylene units in the surfactant. 

Partition Coefficients of Gases, Aliphatic Hydrocarbons, and Aromatic Hydrocarbons... 

The partition coefficients of aromatic hydrocarbons and derivatives are presented in Table 6.5. If we compare data with aliphatic hydrocarbons containing the same number of carbon atoms, the partition coefficients of the aromatic compounds are significantly lower, as expected from their respective solubilities in water. It also appears that the partitioning of aromatic compounds is more dependent on the surfactant headgroup than the aliphatic, but data are scarce and few comparisons can be made. 

Because of its nonpolar and hydrophobic character, the mercury-water may serve as a good model interface for the adsorption study and determination of the organic substances that are adsorbed primarily because of hydrophobic expulsion. There is generally a proportionality of adsorbability (free energy of adsorption) found at the mercury electrode to a number of -CH2 groups in paraffinic hydrocarbon residues in nonpolar surfactants and a similar relation between the octanol water partition coefficient and chain length. This was recently also illustrated in the case of adsorption of aliphatic fatty acids (Ulrich ct al., 1988). 

Long-chain and branched hydrocarbons that are primary components of JP-8, include -nonanc, -dccanc, -dodccanc, -tridecane, isopropylbenzene, -propylbcnzcnc, trirnethylbenzene, -dimcthylbenzene, naphthalene, n-pentylbenzene, and -tricthylbcnzcnc. Inhaled long-chain aliphatic hydrocarbons generally show poor blood uptake because of lower blood solubility. They have relatively high lipid blood partition coefficients this can result in accumulation in lipid-rich tissues, such as brain and fat. In laboratory studies, brain concentrations of hydrocarbons and their metabolites greatly exceed their plasma concentrations. 

Few measurements of important parameters are as simple to make as the partition coefficient of a solute between water and octanol. The principles of the shake-flask measurements remain the same as in the Berthelot and Jungfleisch reports of 1872 and the further analysis by Nemst. Yet the interplay of solvation forces in both the water and octanol phases are so involved and complex that current molecular mechanics and quantum chemical calculations can dispel very little of the empiricism that now dominates logP estimation. It is difficult to predict how soon ab initio calculations will give us dependable information regarding the conformation, the tautomeric form, and the electron distribution of complex solutes, not just as they exist in a vacuum or crystal, but also as they exist in the aqueous phase as well as the water-saturated octanol phase. At present the quantum chemical methods that look the most promising for the complex solutes seem to fail when applied to the simplest hydrophobic organic structures of all the aliphatic hydrocarbons. 

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