Hexane aqueous solution data

In several previous papers, the possible existence of thermal anomalies was suggested on the basis of such properties as the density of water, specific heat, viscosity, dielectric constant, transverse proton spin relaxation time, index of refraction, infrared absorption, and others. Furthermore, based on other published data, we have suggested the existence of kinks in the properties of many aqueous solutions of both electrolytes and nonelectrolytes. Thus, solubility anomalies have been demonstrated repeatedly as have anomalies in such diverse properties as partial molal volumes of the alkali halides, in specific optical rotation for a number of reducing sugars, and in some kinetic data. Anomalies have also been demonstrated in a surface and interfacial properties of aqueous systems ranging from the surface tension of pure water to interfacial tensions (such as between n-hexane or n-decane and water) and in the surface tension and surface potentials of aqueous solutions. Further, anomalies have been observed in solid-water interface properties, such as the zeta potential and other interfacial parameters. 

Tetrachloro-p-quinone (1.2 g) and 3-N,N-diethylaminophenol (1.80 g) were dissolved in 50 ml methyl alcohol, 4.2 ml 28% aqueous solution sodium methoxide added, and the mixture refluxed 6 hours. Thereafter, the mixture was extracted with CH2CI2, dried, and concentrated. The product was purified by chromatography on silica gel using chloroform/hexane and cis- and trans-products, 0.42 g and O.lOg, mp = 292 °C and 288 °C isolated, respectively. H-NMR and absorption maxima and coefficients data supplied. 

Figure 1.32 deals with adsorption of palmitic acid from hexane to the oil-water interface, using the drop volume method. As the drop volume method is relatively slow, the initial decay from the pristine hexane-water interfacial tension to the first reported data cannot be given. Otherwise stated, the data refer to the later stages of diffusion. The trend is that equilibration is somewhat slower than the adsorption of surfactants from aqueous solution. 

Experimental results from screening tests to assess phase transfer witl C8PE95 and phenanthrene partitioning from aqueous surfactant solutioi to hexane support this conclusion. In such tests >90% of the micella 14C-phenanthrene transferred to a hexane phase in less than 1 day fron aqueous solution having surfactant concentration of 500 X CMC. In sue systems there is also the transfer of a fraction of the surfactant to the hexam phase. However, data of Harusawa et al. (60) suggested that for a test witl 500 X CMC only 5% of the surfactant would be transferred to the hexam phase. 

If the silica is treated with fluoride prior to titanation, which converts many of the silanol groups into Si-F surface groups, the reaction with titanium alkoxide is inhibited and the treatment is less effective. The data in Table 34 illustrate this outcome. Silica samples were treated (or not) with two fluoride compounds in aqueous solution, then they were dried at 260 °C in the normal way prior to titanation. Titanium isopropoxide was added to make the catalyst contain 5 wt% Ti. Each sample was then calcined at 815 °C in air. Chromium was applied (0.5 wt%) as bis(f-butyl) chromate) in hexane solution (two-step activation, see Section 12). After final activation in air at 315 °C, each sample was tested at 102 °C, and the polymer MI values obtained are listed in the table. The change in MI shows that the titanium did not attach well to the carrier in the presence of fluoride. As more fluoride was added, the polymer MI dropped. 

Recently St. Angelo et al. (38 ) presented data reaffirming their previous observation that hexanal is an enzymically produced volatile product of the peanut lipoxygenase-linoleic acid reaction. They also confirmed the observations of Pattee and co-workers (33) that pentane is present in the headspace volatiles from the reaction. St. Angelo et al. (38) further showed that care must be excerised to prevent pentane artifacts from arising from the known thermal degradation of hydroperoxide products (39) present in the aqueous solution. 

Finally, just as thermophoresis has as a limit thermal diffusion- in dilute gas mixtures, so one would expect a thermophoretic effect on particles suspended in dense gases and liquids, whose limit would be thermal diffusion of mixtures in these media. The photophoretic effect may have been observed by BARKAS [2.145] in aqueous solutions of colloids. More recently, McNAB and MEISEN [2.146] have reported experimental evidence of thermophoresis in liquids for 1.011 and 0.79 ym spheres in water and n-hexane. They report that their data for the thermophoretic velocity are described by an empirical equation... 

Fig. 2 Interfacial tension isotherms for aqueous solutions of CnTAB in 10 mM phosphate buffer (pH 7) at the solution/hexane vapor interface symbols are experimental data taken from [18] bold curves, values calculated from Eqs. (7)-(9) using the parameters summarized in Table 2 dashed curves are adsorption data at the solution/eiir interface re-plotted from Fig. 1...

Tin literature there are many studies on the adsorption of ionic surfactants at aqueous solution/alkane interface, such as [11, 26, 28-31]. A direct comparison of the adsorption behaviour of CnTAB with alkyl chain lengths 10, 12, 14 and 16 at the water/air and water/hexane interfaces was presented in [8] and it was shown that the FIC model described the experimental data for both interfaces quite well. The new model proposed in [6], leading to the set of Eqs. (7), (9) and (10), has shown to be superior over the FIC model as it allows to assume that the oil molecules provide not only a hydrophobic environment for the adsorbing surfactant molecules but the adsorb themselves at the interface. The equilibrium interfacial tension isotherms presented in Fig. 3 for four CnTABs (n = 10, 12, 14 and 16) adsorbed at the aqueous phosphate buffer solution/hexane interfaces allow to demonstrate the feasibility of the given physical picture of a co-adsorption of surfactant and alkane molecules. 

Mukerjee and Handa [102-104] measured surface and interfacial tensions of dilute aqueous solutions of sodium perfluorobutyrate, sodium perfluorooc-tanoate, sodium perfluorodecanoate, sodium octyl sulfate, and sodium decyl sulfate at the air-water, hexane-water, and perfluorohexane-water interfaces. The surface and interfacial tension values, 7. were converted to interfacial pressures, n, where II = 70 — 7. The data obtained for dilute solutions indicated the affinity of the surfactant for the interface. 

The most critical decision to be made is the choice of the best solvent to facilitate extraction of the drug residue while minimizing interference. A review of available solubility, logP, and pK /pKb data for the marker residue can become an important first step in the selection of the best extraction solvents to try. A selected list of solvents from the literature methods include individual solvents (n-hexane, " dichloromethane, ethyl acetate, acetone, acetonitrile, methanol, and water ) mixtures of solvents (dichloromethane-methanol-acetic acid, isooctane-ethyl acetate, methanol-water, and acetonitrile-water ), and aqueous buffer solutions (phosphate and sodium sulfate ). Hexane is a very nonpolar solvent and could be chosen as an extraction solvent if the analyte is also very nonpolar. For example, Serrano et al used n-hexane to extract the very nonpolar polychlorinated biphenyls (PCBs) from fat, liver, and kidney of whale. One advantage of using n-hexane as an extraction solvent for fat tissue is that the fat itself will be completely dissolved, but this will necessitate an additional cleanup step to remove the substantial fat matrix. The choice of chlorinated hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride should be avoided owing to safety and environmental concerns with these solvents. Diethyl ether and ethyl acetate are other relatively nonpolar solvents that are appropriate for extraction of nonpolar analytes. Diethyl ether or ethyl acetate may also be combined with hexane (or other hydrocarbon solvent) to create an extraction solvent that has a polarity intermediate between the two solvents. For example, Gerhardt et a/. used a combination of isooctane and ethyl acetate for the extraction of several ionophores from various animal tissues. 

Aquan-Yuen, M., Mackay, D., Shiu, W.Y. (1979) Solubility of hexane, phenanthrene, chlorobenzene, and p-dichlorobenzene in aqueous electrolyte solutions. J. Chem. Eng. Data 24, 30-34. 

To 3-methyl-oxetane methanol (20.4 g) was added 50% aqueous NaOH (268 g), NBU4CI (2.8 g) and 300 ml hexane at ambient temperature. Thereafter, allyl bromide (19.4 g) was added drop wise and the solution refluxed 2 hours. The solution was cooled, the phases separated, and the aqueous phase extracted with EtOAc and added to the organic phase. The solvent was removed by distillation and the product isolated in 61% yield in 98% purity. H-NMR data supplied. 

Aqueous 10% NaOH (19.0 mmol) was added to a solution of the product from Step 4 (4.81 mmol) dissolved in methyl alcohol, the mixture stirred at 60 °C 3 hours, acidified with 2M HCl, and extracted with diethyl ether. The solution was washed with brine, dried, filtered, concentrated, purified by chromatography using EtOAc/hexane, 4 6, and the product isolated in 31% yield. H-NMR data supplied. 

To a solution of D-valine (54.6 mmol) dissolved in 62 ml water and 25 ml acetone was added triethylamine (117 mmol). The solution was cooled to 0°C and 4-fluorobenzenesulfonyl chloride (51.4 mmol) dissolved in 25 ml acetone added dropwise. After stirring at ambient temperature 20 hours, the solution was concentrated, the aqueous residue extracted twice with 50 ml toluene and then acidified with HCl to pH 1. The solution was extracted 3 times with 50 ml EtOAc, washed successively with 50 ml apiece of KHSO4, water, and brine, dried, concentrated, and triturated with hexane. The product was isolated in 89% yield. MS and elemental analysis data supplied. 

A solution of triphenylphosphine (1.1 mmol) dissolved in 6 ml CH2CI2 was cooled to 0°C, N-bromosuccinimide (1.1 mmol) added, stirred 30 minutes, and the product from Step 5 added (0.55 mmol). The solution was stirred 15 minutes, warmed to 25 °C, and stirred an additional 90 minutes. The mixture was then treated with 2-aminothiazole (2.75 mmol), stirred 48 hours, and concentrated. The residue was treated with 50 ml EtOAc, 25 ml 1M HCl, and the layers separated. The aqueous layer was extracted with EtOAc, organics combined, washed with 50 ml apiece 1M HCl, NaHC03 solution and brine, dried, and concentrated. The residue was purified by flash chromatography on silica gel using hexanes/EtOAc, 2 1, and the product isolated in 36% yield. Elemental analysis and MS data supplied. 

Fig. 6.9. Intrinsic viscosity [q] as a function of the moiar mass for the rod-iike poiymers deoxyribonucieic acid (DNA) in aqueous NaCI solution at 20 X (data from [47,104]) and poly(hexylisocyanate) (PHIC) in hexane at 25 X (data from [47,105]). At very high molar mass even rod-like polymers behave like flexible coils and show the slope of a flexible coil in a good solvent...

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