Miscibility solvents

Since the 0 s are fractions, the logarithms in Eq. (8.38) are less than unity and AGj is negative for all concentrations. In the case of athermal mixtures entropy considerations alone are sufficient to account for polymer-solvent miscibility at all concentrations. Exactly the same is true for ideal solutions. As a matter of fact, it is possible to regard the expressions for AS and AGj for ideal solutions as special cases of Eqs. (8.37) and (8.38) for the situation where n happens to equal unity. The following example compares values for ASj for ideal and Flory-Huggins solutions to examine quantitatively the effect of variations in n on the entropy of mixing. 

Reduction of Solubility. It is possible to remove a solid from a solution by changing the condition of a solvent. One method is the addition of a second solvent miscible with the first, in which the solid in solution is relatively... 

Ionic liquid -i- catalyst -i- No upper phase a co-solvent miscible with the ... 

In certain cases where the heteroaromatic amine is insufficiently soluble in aqueous acid, it can be dissolved in the minimum volume of an organic solvent miscible with water. Dilute mineral acid and a solution of sodium nitrite are then added. An example is the diazotization of 2-phenyl-3-amino-4-acetyl-5-methyl-pyrrole (Dattolo et al., 1983). 

Ashkenazi, G., Weaver, G. C. (2007). Using lecture demonstrations to promote the refinement of concepts The case of teaching solvent miscibility. Chemistry Education Research andPractice, 8, 186-196. 

Solubility Water Organic solvents Miscibility <0.1 mL No data <1000 ppm No data <1000 ppm No data Insoluble Soluble in hydrocarbon solvents... 

Organic solvents) Miscible with alcohol, chloroform, ether Merck 1989... 

Figure 2.6 A temperature-composition diagram showing the relationship of temperature and solvent miscibility for two partially miscible liquids...

Addition of a cosolvent is an alternative mechanism to increase contaminant solubility in an aqueous solution. When a contaminant with low solubility enters an aqueous solution containing a cosolvent (e.g., acetone), the logarithm of its solubility is nearly a linear function of the mole fraction composition of the cosolvent (Hartley and Graham-Bryce 1980). The amount of contaminant that can dissolve in a mixture of two equal amounts of different solvents, within an aqueous phase, is much smaller than the amount that can dissolve solely by the more powerful solvent. In the case of a powerful organic solvent miscible with water, a more nearly linear slope for the log solubility versus solvent composition relationship is obtained if the composition is plotted as volume fraction rather than mole fraction. 

Solvents, UV cut-olf values, 70 Solvents, miscibility, 75 Solvophobic effect, 201,203 Solvophobic inleHlclidHk, IS2, 20i Solvophobic ion chromatography, 242 Solvophobic theory, 141,148,152,155, 158, 202, 203, 226, 228, 246 8omatostedn, 263,290 Sorbents, polymeric, 127 Sorption isottom, 159 Soiption kineties, efbet on column effi-cieney in RPC, 227 Speed of aepantion, optimization [Pg.172]

Expression of the catalytic capacity of the immobilized laccase was also observed in more than a dozen different solvents, provided that they were either saturated with water or, in the case of solvents miscible with water, small amounts of water had been added (Table III). No enzymatic reaction was observed when the solvents tested were free of water. No correlation was found between the activity of the immobilized laccase and the hydrophobicity of the solvent in which the reaction took place. The rate of laccase reaction in ethylacetate was only twice that in toluene, despite the fact that water-saturated ethylacetate contains 50 times more water than... 

A co-solvent with properties and reaction enhancements similar to HMPA. It is a dipolar aprotic solvent, miscible in water and most organic solvents. Can be cooled to dry ice temperature. 

Notes A polar, aprotic solvent miscible in water and many organic solvents. Efficiently solvates cations. Can greatly enhance the rates of nucleophilic displacement reactions. 

L.A.Burrows, USP 2388901(1945)(Heating device operated like a gasoline torch for expl rivets) 24)DuPont Co L.A.Burrows, BritP 568109(1945) CA 41, 2900(1947)(Initiating compns produced by mixing DADNPh with nitrated polyhydric ales, such as HNMnt, and a solvent miscible with HaO in which DADNPh is insol HNMnt is sol) 25)DuPont Co, L.A. Burrows et al, BritP 572056(1945) CA 41,... 

Inject 10 to 50 pi of sample (see Support Protocol 2) and any optional internal standard dissolved in a solvent miscible with the mobile phase (e.g., ethanol, methanol, acetonitrile). 

Samples extracted into strong organic solvents (hexane, ether, pet ether, ethyl acetate, etc.) must be transferred into a solvent miscible with the mobile phase. A small volume (e.g., 1 ml) of the organic extract should be evaporated under N2 gas and dissolved in reagent alcohol. Further dilutions with alcohol may be necessary to obtain 5 to 10 mg/liter concentration before HPLC injection. 

Special Methods.—With some substances it is difficult to obtain good crystals by the methods already described. A method which frequently gives excellent results consists in dissolving the substance in some solvent, then adding a second solvent miscible with the first, but in which the substance is sparingly soluble. The first solvent is then gradually removed and the substance separates out—usually in the crystalline form. If the first solvent is the more volatile in air, spontaneous evaporation in air may diminish its concentration in the solution. The solution may be placed in a desiccator over some substance which absorbs the first solvent but not the second in this way water may be removed from a water-alcohol solution by solid caustic potash or quicklime. 

The last resort is to wash all the way to hexane and back. Since aqueous solutions and hexane are immiscible, it is necessary to go through a bridging solvent(s). This means washing with one or more solvents miscible with both water and hexane. Common bridges are acetonitrile and chloroform, tetrahy-drofuran (THF), and isopropanol (z -PrOH). THF is probably the easiest and... 

MW 290.19 CAS [107-49-3] an organophosphorus pesticide colorless liquid hygroscopic boiling point 124°C at 1 mm Hg vapor pressure 0.00047 torr at 20°C decomposes at 170 to 213°C density 1.185 g/ml at 20°C miscible with most organic solvents miscible with water but rapidly hydrolyzed highly toxic. 

Solvent manufacturer Honeywell Burdick Jackson [39] defines solvents as miscible if the two components can be mixed together in all proportions without forming two separate phases. A solvent miscibility chart (Figure 2.12) is a useful aid for determining which solvent pairs are immiscible and would therefore be potential candidates for use in LLE. More solvent combinations are miscible than immiscible, and more solvents are immiscible with water than with any other solvent. Solvents miscible with water in all proportions include acetone, acetonitrile, dimethyl acetamide, N,N-dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, ethyl alcohol, glyme, isopropyl alcohol, methanol, 2-methoxyethanol, /V-methyI pyitoI idone. n-propyl alcohol, pyridine, tetrahydrofuran, and trifluoroacetic acid [40]. 

Figure 2.12. Solvent miscibility chart. (Reprinted with permission from Ref. 39. Copyright 2002 Honeywell Burdick Jackson.) Available online at...

If the sample matrix is organic solvent miscible, is it miscible only in nonpolar organic solvents such as hexane, or is it also miscible in polar organic solvents such as methanol ... 

Reference Electrodes for Use in Nonpolar Solvents. Solvents such as dichloromethane (not highly polar) present special problems. Their low dielectric constants promote extensive ion association, and cell resistances tend to be large. For this reason they are often used in mixtures with more polar solvents. Because dichloromethane and other nonpolar solvents are not miscible with water, use of an aqueous reference electrode with such solvents is not practical unless a salt bridge with some mutually miscible solvent is used. A better approach is to use a reference electrode of known reliability prepared in a solvent miscible with dichloromethane or to use the reference electrode based on the half-cell in dichloromethane.88... 

Interface between two liquid solvents — Two liquid solvents can be miscible (e.g., water and ethanol) partially miscible (e.g., water and propylene carbonate), or immiscible (e.g., water and nitrobenzene). Mutual miscibility of the two solvents is connected with the energy of interaction between the solvent molecules, which also determines the width of the phase boundary where the composition varies (Figure) [i]. Molecular dynamic simulation [ii], neutron reflection [iii], vibrational sum frequency spectroscopy [iv], and synchrotron X-ray reflectivity [v] studies have demonstrated that the width of the boundary between two immiscible solvents comprises a contribution from thermally excited capillary waves and intrinsic interfacial structure. Computer calculations and experimental data support the view that the interface between two solvents of very low miscibility is molecularly sharp but with rough protrusions of one solvent into the other (capillary waves), while increasing solvent miscibility leads to the formation of a mixed solvent layer (Figure). In the presence of an electrolyte in both solvent phases, an electrical potential difference can be established at the interface. In the case of two electrolytes with different but constant composition and dissolved in the same solvent, a liquid junction potential is temporarily formed. Equilibrium partition of ions at the - interface between two immiscible electrolyte solutions gives rise to the ion transfer potential, or to the distribution potential, which can be described by the equivalent two-phase Nernst relationship. See also - ion transfer at liquid-liquid interfaces. 

If the solvents are immiscible, the LC system will fail. If the pump will be delivering an eluent that is not soluble with the previous mobile phase or if the new mobile phase consists of two immiscible solvents, the net result is to have tiny slugs of different solvents traveling through the HPLC. Typical indications of this problem are (1) erratic flow rate, (2) noisy baseline, and/ or (3) baseline drift. To insure that these problems are not caused by a mismatch of solvents, refer to Table 6-4 for the miscibility numbers (M) and their use. The discussion on determining solvent miscibility using miscibility numbers is adapted from reference 20. 

We use a solvent miscible with both oil and hydrogen, thus forming a substantially homogeneous phase to pass the catalyst surface. The solvent is near-critical or supercritical propane. The oil does not prevent the hydrogen from entering the pores of the catalyst anymore. 

Examples from patents [S. Haber and N. Egger, US Patent 6 140 265 (2000), to Clariant S. Haber and H.-J. Kleiner, US Patent 5 756 804 (1998), to Hoechst-Clariant] describe the synthesis of 2-cyano-4 -methylbiphenyl by reaction of 2-chlorobenzonitrile and p-tolueneboronic acid, in the presence of Na2C03, PdCl2, and triphenylphosphinetrisulfonic acid (4 mol) in a water-toluene system, with a co-solvent miscible with water such as DMSO or... 

The different properties of ILs, with regard to their polarity, hydrophobicity, and solvent miscibility behavior through combination with different anions, are the reason for the different biocatalyst activities. Good to excellent activity of CALB was observed with a decrease in polarity and hydrophobicity and a viscosity increase of the ILs. In [bmim][PF6] a conversion of (R)-l-phenylethanol into the ester of 48.9% and an ee of 95.6% were achieved after 5h and 100% of (R)-l-phenylethanol was converted into the enantiopure (R)-l-phenylethyl acetate after a 1-day reaction. Immobilized CALB exhibited excellent stability, activity, and selectivity towards the (R)-enantiomer of 1-phenylethanol in [bmim][PF6]. In some research bis(trifluoromethylsulfonyl)imide-based ILs have been regarded as very suitable media for biocatalysis [39, 46, 50]. On the contrary, in the present work, lower suitability of the same IL was demonstrated. Since immobilized CALB catalyzed both hydrolytic and transesterification reactions, its enantioselectivity for long reaction times was lower. 

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