Alcohol-water systems

Donahue and Bartell verified Eq. IV-16 for several organic alcohol-water systems. 

The amino group is readily dia2oti2ed in aqueous solution, and this reaction forms a basis for the assay of sulfas. Aldehydes also react to form anils, and the yellow product formed with 4-(dimethylamino)hen2a1dehyde can be used for detection in thiu-layer and paper chromatography. Chromatographic retention values have been deterrnined in a number of thiu layer systems, and have been used as an expression of the lipophilic character of sulfonamides (23). These values have corresponded well with Hansch lipophilic parameters determined in an isobutyl alcohol—water system. 

Crosslinked gel systems Alcohol-water systems Increase viscosity... 

Cubic equations have been used for several alcohol/water systems, and also for the 2-propanol/CO ater system (as well as for numerous... 

Kasrajan, K., De Lucca, P. O. Thermal analysis of tertiary butyl alcohol-water system and its implication on freeze-drying. Pharm. Res. 12 (4), p. 484—90, 1995... 

Let s make a comparison of individual cases. Figures 5-7 show the cases where CaCk was added to the alcohol-water system. Figure 5 shows the values observed by the author when the salt concentration was constant in terms of mole fraction, according to which the hydration number So of salt with water is 11 at 3 = 0.020,10 at x3 = 0.040, and 6 at 3 = 0.100. The value of So decreases as the salt concentration increases. The reason for this may be that the activity of salt decreases and the number of molecules to be solvated decreases as the salt concentration increases. Our calculation was made using the data obtained by Yoshida et al. (16). As we obtained almost the same results as those shown in Figure 5, graphic representation is omitted. 

Alcohols exhibit a bifunctional nature in aqueous solution. On the one hand, there exists a hydrophobic hydrocarbon group which resists aqueous solvation on the other, there is the hydrophilic hydroxyl group which interacts intimately with the water molecules. Franks and Ives (30, 31) have reviewed experimentation and theoretical treatises on the structure of water, the structure of liquid alcohols, and the thermodynamic, spectroscopic, dielectric, and solvent properties and P-V-T relationships of alcohol-water mixtures. Sada et al. (27) reviewed, in particular, the salt effects of electrolytes in alcohol-water systems and discussed the various correlations of the salt effect applied to these systems. Inorganic salts were used almost universally in these salt effect studies. 

The heats of solution and dilution of electrolytes in nonaqueous-aqueous solvent mixtures have been limited mostly to alcohol-water systems and a few measurements in dimethylsulfoxide-water and dioxane-water mixtures (J, 2). The structural maximum in aqueous-organic solvents at high water content has been well established by a variety of techniques (3,4), but few systems have been explored over the whole composition range. 

Coffander-iype Relationships Collander has studied partition coefficients in different alcohol-water systems [16]. He found that these partition coefficients are mutually correlated. For certain compounds containing one hydrophilic group, such as alkanols, alkanoic acids, alkanoates, dialkyl ethers, and alkylamines and selected compounds containing two, three, or four such groups, he reports the following equation ... 

As can be seen in figure 6.1 and 6. 2 a heterogeneous system exhibits interfaces or planes of separation whereas a homogeneous one does not. By increasing the temperature of the alcohol - water system, we can create a vapour phase next to the liquid phase (figure 6.3). Vapours are completely miscible which means that at most one vapour phase can occur in a system. 

Pervaporation is a membrane separation process where the liquid feed mixture is in contact with the membrane in the upstream under atmospheric pressure and permeate is removed from the downstream as vapor by vacuum or a swept inert gas. Most of the research efforts of the pervaporation have concentrated on the separation of alcohol-water system [1-20] but the separation of acetic acid-water mixtures has received relatively little attention [21-34]. Acetic acid is an important basic chemical in the industry ranking among the top 20 organic intermediates. Because of the small differences in the volatility s of water and acetic acid in dilute aqueous solutions, azeotropic distillation is used instead of normal binary distillation so that the process is an energy intensive process. From this point of view, the pervaporation separation of acetic acid-water mixtures can be one of the alternate processes for saving energy. 

B. Will, R.N. Lichtenthaler, Comparison of the separation of mixtures by vapor permeation and pervaporation using PVA composite membranes. Part I. Binary alcohol—water systems, J. Membr. Sci. 68 (1992) 119-125. 

Ternary acetate-alcohol-water systems (propyl, butyl, amyl, hexyl) 178 Azeotrope problem ... 

On the basis of the above mentioned workup procedure a new simultaneous resolution method was developed using two moles of racemic tetrahydrofuroic acid (3b) instead of 12 for decomposition of complex 11 (Scheme 6, L= 8). In a methyl alcohol/water system the (S)-3b isomer built up a new crystalline coordination complex (13) while two moles of (R)-8 liberated and one mole of (R)-3b remained in the solution. [25]... 

Reductive dehalogenation is an efficient method of synthesis of cyclopropanes spiroannulated to five- and higher-membered carbocycles (i.e. compounds in which spiroannulation does not result in accumulation of extra strain) . The required gem-(dihalomethyl)cycloalkanes are usually prepared by halogenation of the precursor diols (equation 1). The cyclization is most efficiently accomplished in the Zn-alcohol-water system . For example, spiro[2.5]octane 7 was prepared in 91% yield using this procedure. This method is useful even for a one-step preparation of bis-spirocyclopropyl compounds as exemplified in equation 2. However, the application of the reductive dehalogenation method to the synthesis of more strained SPC (i.e. spirohexane or spiropentane) often leads to rearranged products. For example, methylenecyclopentane was the only product obtained from bis(bromomethyl)cyclobutane (equation 3) ... 

Minh, L. V. Nose, T., "Phase Equilibrium of Poly(acrylic acid) Partially Neutralized by NaOH-Poly(vinyl alcohol)-Water System," Polym. J., 15, 145 (1983). 

Sakurada, I. Nakajima, A. Fujiwara, H., "Vapor Pressures of Polymer Solutions. II. Vapor Pressures of the Poly(vinyl alcohol)-Water System," J. Polym. Sci., 35, 497 (1959). 

The vapor-liquid equilibrium data for the 3-methyl-l-butanol-water system are shown in Table III and Figure 4. The boiling point measurements agreed with those reported in Timmermans (13). The value of a = 0.45 as suggested by Renon and Prausnitz (8) for alcohol-water systems was not suitable. Various other values of a were tried, and a value of a. = 0.3 was found to agree best. This fit can be established by using the method described to test the consistency of the equations—i.e., the... 

Over 20 years ago Collander (2) showed that there was a linear relationship between the log F values measured in any two alcohol/ water systems. 

The transfer free energy (as measured by the slope value) for any solute in an alcohol/water system should decrease as the chain length of the solvent alcohol is shortened. Of course the same effect ought to be observed if we hold the oil phase constant and make the aqueous phase less hydrophilic. The equations in Table V show that for a limited set of barbiturates partitioned between diethyl ether and a 50-50 mixture of water and dimethylformamide, the slope, compared with the octanol standard, is only 0.4 whereas the ether/water system gives a slope for the donor solute group of 1.13. Thus, a 50% reduction in the protic character of the polar phase reduces the sensitivity of the system by a factor of 2.8. 

For humans (9), the correlation is not as good as those found for rabbits and rats (Equations 48-50). This may be the result of the small variability of values on the left of the equation and of the difference in the ability of partition coefficient data to define permeability in the different test animals. If we use i/ values derived from the partition coefficients with a CHC13—water system instead of those from an isobutyl alcohol-water system, Equation 52 results, which shows a reasonable correlation. This is the only example here where the values from a CHCl3-water system show a better correlation than those from an isobutyl alcohol-water system. The susceptibility of human tubular reabsorption to the hydrophobicity of drugs might be different from those of the rat and rabbit thus, the model with a CHCl3-water system could simulate... 

Until more data is collected in the various alcohol-water systems, and better models for these systems are developed, it will be impossible to definitely delineate the processes occurring in these solvent systems. 

A single relaxation was observed for the binary water-surfactant system and the results obtained are in good agreement with those previously reported [8]. A relatively weak sound absorption (ca. 1-4 MHz) is apparent in alcohol-water systems for the more concentrated solutions of Bu and Pe. 

Lipolysis in isolated fat cells has been measured by determining free fatty acids and glycerol [173]. Free fatty acids were determined after extraction with a two-phase heptane-isopropyl alcohol-water system [174], whereas glycerol was determined by a coupled enzymatic assay which involves formation of glycerol-3-phosphate by ATP, oxidation of glycerol-3-phosphate with NAD, and measuring the native fluorescence of NADH [175]. 

Rheology of lyotropic liquid crystals for binary polyoxy- 80. ethylene fatty alcohol/water systems. II. The hexagonal mesophase. In Process and Trends in Rheology 11 ... 

The alcohol—water systems have attracted attention " for a number of reasons ... 

The calculated correlation volumes and energetic parameters for the alcohol—water and hydrocarbon—water systems are hsted in Tables 4 and 5. The calculated volumes are compared with the sizes of clusters in several alcohol/water systems determined by small-angle X-ray scattering or light scattering " at low concentrations (Table 6). Table 6 shows that there is reasonable agreement between them and the calculated correlation volumes at infinite dilution. 

Alcohol/Water Systems and Size of Ousters at Small Concentration of Alcohol in These Systems Obtained by ... 

Tables 4 and 5 also list the values of the energy interaction parameters Tij for the alcohol/water and hydrocarbon/water systems. For the alcohol/water systems, the parameters were calculated for both dilute solutions of alcohol in water and dilute solutions of water in alcohol. For hydrocarbon/water systems, the calculations were carried out only for dilute solutions of hydrocarbon in water, because no experimental information could be found for the solutions of water in hydrocarbons. Figure 3 presents a plot of F12 versus the number of carbon atoms in molecules for normal alcohols and hydrocarbons.

Figure 3. Energetic parameter Fn (J/mol) as a function of the number of carbon atoms in alcohol and hydrocarbon molecules (n) ( ) alcohol/ water systems and ( ) hydrocarbon/water systems.

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