Heptane/water systems

FIG. 25 Interfacial tension isotherms for homologous n-alkanesulfonates and a disulfonate mixture in the heptane/water system (1-9 RS03Na, R = C9H20 to C17H36 10 disulfonate mixture). 

The heptane water and toluene water interfaces were simulated by the use of the DREIDING force field on the software of Cerius2 Dynamics and Minimizer modules (MSI, San Diego) [6]. The two-phase systems were constructed from 62 heptane molecules and 500 water molecules or 100 toluene molecules and 500 water molecules in a quadratic prism cell. Each bulk phase was optimized for 500 ps at 300 K under NET ensemble in advance. The periodic boundary conditions were applied along all three directions. The calculations of the two-phase system were run under NVT ensemble. The dimensions of the cells in the final calculations were 23.5 A x 22.6 Ax 52.4 A for the heptane-water system and 24.5 A x 24.3 A x 55.2 A for the toluene-water system. The timestep was 1 fs in all cases and the simulation almost reached equilibrium after 50 ps. The density vs. distance profile showed a clear interface with a thickness of ca. 10 A in both systems. The result in the heptane-water system is shown in Fig. 3. Interfacial adsorption of an extractant can be simulated by a similar procedure after the introduction of the extractant molecule at the position from where the dynamics will be started. 

FIG. 6 Measurements of the interfacial adsorptivity and the extraction rate from the absorbance changes of the organic phase by means of the high-speed stirring method, (a) Heptane-water system... 

This screening concept was also applied to liquid/liquid systems. As a test reaction, the isomerization of allylic alcohols to carbonyls with water-soluble catalysts in a biphasic heptane/water system was chosen [109,113]. The catalysts (metal precursor, Rh, Ru, Pd, Ni ligands, sulfonated phosphane or disphosphane ligands) were injected the liquid carrier 2 (water). The substrates (different allylic alcohols) were injected into liquid carrier 1 (heptane) ... 

Other reliable indicators for hydrogen-bonding are AlogE determined using octa-nol/water - heptane/water systems and octanohwater - chloroform/water systems [El Tayar et al, 1991b]. 

Pd/C also catalyzes the PTC reduction of aryl and heteroaryl halides with sodium formate [52]. The reductive dehalogenation of allyl and benzyl halides with HCOOK can be carried out in a heptane/water system in the presence of water-soluble complexes of type PdCl2(sulfonated phosphine)2 and a PT agent... 

T. M. O Grady, Liquid-Liquid Equilibria for the Benzene-n-Heptane-Water System in the Critical Solution Region, J. Chem. and Eng. Data, 12, 9-12 (1967). 

NaBH4 and zinc chloride (Eq. 7) [16]. These additives are necessary for reduction of the catalyst precursor and for prevention of deactivation of the catalyst by excess cyanide anion in the aqueous phase, respectively. As the use of zinc chloride in a Zn/CN molar ratio of more than 0.25 1 is required, the active cyanide source may be tetracyanozincate or zinc cyanide [26], The efficiency of the counter-PTC in the heptane-water system exceeds that of the mixed catalyst system of lipophilic catalyst and normal PTC, though the cyanide anion is easily extractable by the normal PTCs (Table 6). 

Method Errors. Table 1-11 compares observed and estimated values of K0w for 39 examples, excluding those where KSw was from the cyclohexane/water or heptane/water systems. For the examples listed, the average absolute error is 0.38 log Kow unit and the maximum error is 1.4 log Kow units. The method error for Eq. 1-38 is assumed to be of similar magnitude. 

The anionic AOT-heptane-water system is one of the best characterized microemulsions [40]. Up to 2 m AOT can be solubilized in heptane. The phase diagram was determined by Rouviere et al. [40]. It shows a particularly large L2 region (Fig. 1) in which water can be dispersed, even at very low surfactant concentrations. It is the wedge-shaped structure of the surfactant that favors the reverse micellar association. The reverse micelles can take up to 60 molecules of water per surfactant headgroup. 

The rearrangement rate is quite slow with respect to other microemulsions. For example, for the AOT-heptane-water systems, the rate of fusion is determined to be equal to lO -lO dmV(moI s). There is a difference of three to four orders of magnitude between the rates of fusion of the two microemulsion systems. The differences are even more astonishing if we recall the near-percolating state suggested by the conductivity measurements for the CTAB-hexanol-water microemulsion. 

The diameter of the particles is plotted as a function of micellar droplet concentration in Fig. 15. The values of the particle size are those obtained by interpolation of previous results in the presence of 0.161 m aqueous metal ion for the CTAB-hexanol-water systems. Particles prepared in the AOT-heptane-water system at much lower droplet concentration are included for comparison. 

FIGU RE 2.7 Comparison between the observed distribution constants of halobenzenes and those predicted from the scaled particle theory (solid line) in a heptane/water system. 

E.A. Lissi and D. Engel, Incorporation of n-alkanols in reverse micelles in the AOT/n-heptane/water system, 1992, Langmuir 8, 452-455. 

The nanoparticles have been synthesized in different microemulsion systems. Some of them are shown in Fig. 1. The anionic Aerosol-OT (AOT)/ heptane/water system is one of the best characterized microemulsions [8,9]. The system AOT/ -xylene/water [10] has also been used. The cationic ce-tyltrimethylammonium bromide (CTAB)/hexanol/water system contains hex-anol, which forms the organic phase and plays the role of cosurfactant [11]. The nonionic penta(ethylene glycol)-dodecylether (PEGDE)/hexane/water was studied by Eriberg and Eapczynska [12]. The reverse micellar droplets have a cylindrical shape in which the surfactant molecules are parallel to each other, forming a bilayer impregnated with water. Triton X-100... 

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