Water hexane partition coefficient

The relationship described by equation 4 indicates that most of the variation in carcinogenicity within the series of acyclic nitrosamines can be associated with water-hexane partition coefficients and electronic inductive effects of substituents on the a-carbons. 

The standard free energy of partition was calculated from water-hexane partition coefficients ... 

Wishnok et al. (6) have found the water/hexane partition coefficient P and "electronic factors" as measured by Taft a to correlate with carcinogenic activity for a series of nitroso-... 

Aqueous solutions are not suitable solvents for esterifications and transesterifications, and these reactions are carried out in organic solvents of low polarity [9-12]. However, enzymes are surrounded by a hydration shell or bound water that is required for the retention of structure and catalytic activity [13]. Polar hydrophilic solvents such as DMF, DMSO, acetone, and alcohols (log P<0, where P is the partition coefficient between octanol and water) are incompatible and lead to rapid denaturation. Common solvents for esterifications and transesterifications include alkanes (hexane/log P=3.5), aromatics (toluene/2.5, benzene/2), haloalkanes (CHCI3/2, CH2CI2/I.4), and ethers (diisopropyl ether/1.9, terf-butylmethyl ether/ 0.94, diethyl ether/0.85). Exceptionally stable enzymes such as Candida antarctica lipase B (CAL-B) have been used in more polar solvents (tetrahydrofuran/0.49, acetonitrile/—0.33). Room-temperature ionic liquids [14—17] and supercritical fluids [18] are also good media for a wide range of biotransformations. 

Water 70pgL acetone 560gL ethanollSgL toluene400g L n-hexane 14g L n-octanol6.8g Yellow to orange odorless crystalline solid density 1.54gem at 20°C octanol/water partition coefficient (log P)5.45 at 25 °C... 

Readily soluble in organic solvents ethanol 51, acetone 77,toluene 63, n-octanol 13, n-hexane 0.53 g per 100 mL Colorless to white solidified melt, no dissociation constant in an accessible pH range, octanol/water partition coefficient (log /Cow) 4.07 at 25 °C. 

The octanol-water partition coefficient appears to correlate better with biological activity than partition coefficients in other solvent-water mixtures as, for example, hexane water, because the amphiphilic nature of octanol can accommodate a greater variety of more or less hydrophobic molecules. 

The physical properties of -hexane (see Table 3-2) that affect its transport and partitioning in the environment are water solubility of 9.5 mg/L log Kow (octanol/water partition coefficient), estimated as 3.29 Henry s law constant, 1.69 atm-m3 mol vapor pressure, 150 mm Hg at 25 °C and log Koc in the range of 2.90 to 3.61. As with many alkanes, experimental methods for the estimation of the Koc parameter are lacking, so that estimates must be made based on theoretical considerations (Montgomery 1991). 

The dominant transport process from water is volatilization. Based on mathematical models developed by the EPA, the half-life for M-hexane in bodies of water with any degree of turbulent mixing (e.g., rivers) would be less than 3 hours. For standing bodies of water (e.g., small ponds), a half-life no longer than one week (6.8 days) is estimated (ASTER 1995 EPA 1987a). Based on the log octanol/water partition coefficient (i.e., log[Kow]) and the estimated log sorption coefficient (i.e., log[Koc]) (see Table 3-2), ii-hexane is not expected to become concentrated in biota (Swann et al. 1983). A calculated bioconcentration factor (BCF) of 453 for a fathead minnow (ASTER 1995) further suggests a low potential for -hcxanc to bioconcentrate or bioaccumulate in trophic food chains. 

The sorption of two weak acids (warfarin and thiopentone) and two weak bases (chlorpromazine and diltiazem) into PVC infusion bags was described by a constant partition model. PVC-water partition coefficients were obtained using three different methods equilibrium values for sorption into PVC bags, the sorption versus pH relationship, and partition into PVC strips. The data were compared with similar values derived from a liquid-liquid partition system and different organic solvents (octanol, dichloromethane, carbon tetrachloride, and hexane). Octanol is the preferred solvent, and it is suggested that octanol-water partition data can be used to predict sorption behavior [182]. 

In a solute-solvent system of similar polarity (naphthalene in chlorobenzene), Equation (3.34) can estimate the solubility of the liquid solute. If the polarities of the solute and the solvent are very different (naphthalene in n-hexane), Equation (3.34) should be modified. The partition coefficient in the water-octanol system can be used for differences in polarities of the solute and the solvent. The partition coefficient of a liquid solute, Kw0, in the water-octanol system is defined as ... 

Fig. 9. Relationship between the steady-state bioconcentration factors on a lipid basis (BCFl) of chemicals in different fish species and the n-octanol/water partition coefficient (Kqw) (log/log scale). ( ) Solid circles are chemicals with known endocrine-disrupting properties. Abbreviations of the chemicals p,p -DDT 2,2-bis-(p-chlorophenyl)-l,l,l-trichloroethane. OCDD octachlorodibenzo-p-dioxin. TCDD tetrachlorodibenzo-p-dioxin. HCB hexachloro-benzene. PCA pentachloroanisole. PeCB pentachlorobenzene. MX musk xylene. TeCB tetrachlorobenzene. NP nonylphenol. TCB tetrachlorobenzene. y-HCH y-hexachlorocyclo-hexane (Lindane). PCP pentachlorophenol. DCB dichlorobenzene. BPA bisphenol-A. PCBs polychlorinated biphenyls...

The hydroxylation of n-hexane on TS-1, in contrast to the epoxidation of propene, reached its maximum rate in the least polar solvent, t-butanol (Table 18.13). Acetonitrile behaved quite similarly to methanol and water [24, 25, 169]. On the assumption that t-butanol was comparable to i-propanol for the effects on adsorption, a clear relationship between rates and partition coefficients was lacking. Considering that hydroxylation and epoxidation involve different active species and mechanisms, a diverse role of the solvent in the two active species could contribute to the differences, whereas the partition coefficients alone could not... 

We only give basic directions for the choice of a solvent system. If the polarities of the solutes are known, the classification established by Ito [1] can be taken as a first approach. He classified the solvent systems into three groups, according to their suitability for apolar molecules ( apolar systems), for intermediary polarity molecules ( intermediary system), and for polar molecules ( polar system). The molecule must have a high solubility in one of the two immiscible solvents. The addition of a third solvent enables a better adjustment of the partition coefficients. When the polarities of the solutes are not known. Oka s [8] approach uses mixtures of n-hexane (HEX), ethyl acetate (EtOAc), n-butanol (n-ButOH), methanol (MeOH), and water (W) ranging from the HEX-MeOH-W, 2 1 1 (v/v/v) to the n-BuOH-W, 1 1 (v/v) systems and mixtures of chloroform, methanol, and water. These solvent series cover a wide range of hydrophobicities from the nonpolar n-hexane-methanol-water system to the polar n-butanol-water system. Moreover, all these solvent systems are volatile and yield a desirable two-phase volume ratio of about 1. The solvent system leading to partition coefficients close to the unit value will be selected. 

The elution strength of hybrid micellar mobile phases was measured for a number of organic additives (alcohols, alkane diols, alkanes, alkylnitriles, and dipolar aprotic solvents, such as dimethyl sulfoxide and dioxane) added to micellar SDS, CTAC, and Brij-SS. Benzene and 2-ethylanthraquinone were used as probe compounds. The presence of alcohols, alkane diols, alkylnitriles, and dipolar aprotic solvents produced a diminution of the retention times, reaching remarkable levels for the most hydro-phobic compound (2-ethylanthraquinone). The observed elution strength order roughly paralleled the octanol-water partition coefficients of the additives, Rq/w (Fig- 2), or their ability to bind to micelles, am- In contrast, alkanes (pentane, hexane, and cyclohexane) had relatively little effect on the retention. 

Oka et al. [5] proposed a choice of various solvent systems to purify antibiotics. They have to fulfill various criteria. The settling time of the solvent system should be shorter than 30 s to ensure the satisfactory retention of the stationary phase. The partition coefficient of the target compounds should be close to 1, and the separation factor (a) between the compounds must be larger than 1.5. Two series of solvent systems can provide an ideal range of the K values for a variety of samples n-hexane-ethyl acetate-n-bu-tanol-methanol-water and chloroform-methanol-water. These solvent series cover a wide range of hy-drophobicity, continuously, from the nonpolar n-hexane-methanol-water system to a more polar n-butanol-water system. 

These molecules have an intermediary polarity (Fig. 2a). A two-phase solvent system, composed of n-hexane, ethyl acetate, methanol, and water, has been selected. In this case, the partition coefficients, K, are defined as the ratio of the solute concentration in the upper phase to its concentration in the lower one. A solvent mixture of n-hexane-ethyl acetate-methanol-water (19 1 10 10, v/v/v/v) yielded the best K values from 0-2.83. 25 mg of crude ivermectin separated in 4.0 h. This separation yielded 18.7 mg of 99.0% pure ivermectin Bla, 1.0 mg of 96.0 % pure ivermectin Bib, and 0.3 mg of 98.0% pure avermectin Bla. 

In each solvent series,the partition coefficient of the sample can be finely adjusted by modifying the volume ratio of the components. The first series covers a broad range in both hydrophobicity and polarity continuously from M-hexane/methanol/water to n-butanol/water. The second series of chloroform/methanol/water provides moderate hydrophobicity and the third series of ferf-butyl methyl ether/w-butanol/acetonitorile/water is suitable for hydrophilic compounds. Most of these two-phase solvent systems provide near 1 1 volume ratios of the upper/lower phases, together with the reasonable range of settling times in 30 sec or less, so that they can be efficiently applied to HSCCC and other centrifugal CCC schemes. 

For the sample mixmre with an unknown composition, the search for the suitable two-phase solvent system may be initiated with the partition coefficient measurement with n-hexane/ethyl acetate/n-butanol/methanol/water (5 5 0 5 5) (Table 1), chloroform/methanol/water (10 3 7) (Table 2) or ferf-butyl methyl ether/butanol/ acetonitorile/water (6 0 3 8) (Table 3). If the Ai(org/aq) value is too large, the search should be directed toward the more hydrophobic solvent systems and, if the K value is too small, the search should be directed toward the more hydrophilic solvent systems until the proper K values are obtained. 

CL is soluble in water, slightly soluble in alcohols, but insoluble in nonpolar solvents such as hexane and chloroform. Based on these properties, we selected fx-butanol and water as a basic solvent system. However, this combination was not suitable by itself, because the CL components were entirely partitioned into the lower aqueous phase. In order to partition the CL components partly into the n-butanol phase, various salts (sodium chloride and sodium sulfate) or acids (hydrochloric acid, sulfuric acid and TFA) were added as a modifier. A desirable effect was obtained by the addition of TFA, where the partition coefficients of CL components rose as the concentration of TFA in the solvent system was increased. As TFA forms an ion pair with amino groups in the molecule of CL, the hydrophobicity of CL components... 

Some relation has been found between the rate of sorption by poly (vinyl chloride) (PVC) bags of a series of dmgs and their hexane/ water partition coefficients.Table 5.20 shows the data for sorption of 100 cm PVC infusion bags (equivalent to 11 g of PVC). In the table,... 

Ruelle P. The n-octanol and n-hexane/water partition coefficient of environmentally relevant chemicals predicted from the mobile order and disorder (MOD) thermodynamics. Chemosphere 2000 40 457-512. 

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