Short-chain alcohols

Weakly polar oils such as long-chain alcohols, phenols, and long-chain fatty acid esters have often been shown to exhibit antifoam behavior provided they are not so polar as to show high solubility in the relevant aqueous surfactant solutions (see, e.g., references [9, 10, 39, 105]). Arguably the earliest reported observations concerning the antifoam behavior of an alcohol are those of Sasaki [3] more than 70 years 

It is argued by Kruglyakov and Koretskaya [107] that these antifoam effects are due to the formation of asynunetrical films where an oil lens is present on one side of a foam film. As we have seen, lenses will form provided 0 and S 0. They can, in fact, form even if 5 0 because the resulting film may be metastable so that pseudo-partial wetting conditions ultimately prevail at equilibrium and we have 0 and 5 0. These issues are described at length in Chapter 3. 

Kruglyakov [41] suggests that these asymmetric films, separating alcohol drops from air-water surfaces, can be metastable in the same sense as symmetrical air-water-air foam films provided entry coefficients are positive. This represents an early appreciation of the significance of what we now know as pseudoemulsion films. However, he also argues that the pseudoemulsion film will in general have a different stability from that of the symmetrical foam film with the same surfactant solution. This is supposed to arise in part because of differences in surface excess of 

FIGURE 4.27 Limiting alcohol concentrations for foam to exhibit instability at various concentrations of blend of ethoxylated nonyl phenols (in 0.1 M KCl) (1) 1%, (2) 0.1%, (3) 0.5%, (4) 0.025%, (5) 0.005%, and (6) 0.001%. (After Kruglyakov, P.M. Equilibrium properties of free films and stability of foams and emulsions, in Thin Liquid Films, Fundamentals and Applications, Ivanov, I.B., ed., Marcel Dekker, New York, p 767, 1988.) 

Abe and Matsumnra [108] have also considered the antifoam effect of alcohols on the foam behavior of an aqueous solution of sodium dodecylbenzene sulfonate. The alcohols inclnded normal alcohols, branched alcohols, and diols. However, Abe and Matsumura [108] were concerned with the supposed role of the elimination of surface tension gradients under dynamic conditions in determining heterogeneous antifoam effectiveness in the case of these weakly polar oils. We have of course already considered the basic proposition of antifoam action by elimination of surface tension gradients in some detail in Section 4.4.3. 

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Environmental Considerations. Environmental problems in Ziegler chemistry alcohol processes are not severe. A small quantity of aluminum alkyl wastes is usually produced and represents the most significant disposal problem. It can be handled by controlled hydrolysis and separate disposal of the aqueous and organic streams. Organic by-products produced in chain growth and hydrolysis can be cleanly burned. Wastewater streams must be monitored for dissolved carbon, such as short-chain alcohols, and treated conventionally when necessary. 

Selectivity. Solvent selectivity is intimately linked to the purity of the recovered extract, and obtaining a purer extract can reduce the number and cost of subsequent separation and purification operations. In aqueous extractions pH gives only limited control over selectivity greater control can be exercised using organic solvents. Use of mixed solvents, for example short-chain alcohols admixed with water to give a wide range of compositions, can be beneficial in this respect (6). 

PZN-PT, and YBa2Cug02 g. For the preparation of PZT thin films, the most frequently used precursors have been lead acetate and 2irconium and titanium alkoxides, especially the propoxides. Short-chain alcohols, such as methanol and propanol, have been used most often as solvents, although there have been several successful investigations of the preparation of PZT films from the methoxyethanol solvent system. The use of acetic acid as a solvent and chemical modifier has also been reported. Whereas PZT thin films with exceUent ferroelectric properties have been prepared by sol-gel deposition, there has been relatively Httle effort directed toward understanding solution chemistry effects on thin-film properties. 

Tyn-Calus This correlation requires data in the form of molar volumes and parachors = ViCp (a property which, over moderate temperature ranges, is nearly constant), measured at the same temperature (not necessarily the temperature of interest). The parachors for the components may also be evaluated at different temperatures from each other. Quale has compiled values of fj for many chemicals. Group contribution methods are available for estimation purposes (Reid et al.). The following suggestions were made by Reid et al. The correlation is constrained to cases in which fig < 30 cP. If the solute is water or if the solute is an organic acid and the solvent is not water or a short-chain alcohol, dimerization of the solute A should be assumed for purposes of estimating its volume and parachor. For example, the appropriate values for water as solute at 25°C are = 37.4 cmVmol and yn = 105.2 cm g Vs mol. Finally, if the solute is nonpolar, the solvent volume and parachor should be multiplied by 8 Ig. 

ILs are considered to be polar solvents, but can be non-coordinating (mainly depending on the IL s anion). Solvatochromatic studies indicate that ILs have polarities similar to those of short-chain alcohols and other polar, aprotic solvents... 

Bonhote and co-workers [10] reported that ILs containing triflate, perfluorocar-boxylate, and bistrifylimide anions were miscible with liquids of medium to high dielectric constant (e), including short-chain alcohols, ketones, dichloromethane, and THF, while being immiscible with low dielectric constant materials such as alkanes, dioxane, toluene, and diethyl ether. It was noted that ethyl acetate (e = 6.04) is miscible with the less-polar bistrifylimide and triflate ILs, and only partially miscible with more polar ILs containing carboxylate anions. Brennecke [15] has described miscibility measurements for a series of organic solvents with ILs with complementary results based on bulk properties. 

Ionic liquids are similar to dipolar, aprotic solvents and short-chain alcohols in their solvent characteristics. These vary with anion (from very ionic Cl to more covalent [BETI] ). IFs become more lipophilic with increasing alkyl substitution, resulting in increasing solubility of hydrocarbons and non-polar organics. 

The application of microemulsions in foods is limited by the types of surfactants used to facilitate microemulsion formation. Many surfactants are not permitted in foods or only at low levels. The solubilization of long-chain triglycerides (LCTs) such as edible oils is more difficult to achieve than the solubilization of short- or medium-chain triglycerides, a reason why few publications on microemulsions are available, especially because food-grade additives are not allowed to contain short-chain alcohols (C3-C5). 

Examination of the steric relations in these complexes (cf. Fig. 30) suggests that the more voluminous branched alcohols cannot follow the same principle. Indeed, in the 2-butanol and also in the t-butanol inclusion compound, a different ring system is built (Fig. 17b and type I in Fig. 19). While the short-chain alcohols form twelve-membered H-bond loops, the branched butyl alcohols are embedded into a ten-membered asymmetric loop. The stoichiometry of the asymmetric unit also changes from 1 2 (host guest) ratio to 1 1. The so-built ring system of homodromic H-bonds still contains a mirror-related pair of hosts 1, but comprises only one guest molecule. 

Surfactant molecules can be considered as building blocks for certain forms of geometry in colloidal chemistry. Various forms of association molecules can be obtained as the concentration of surfactant in water is increased and/or physicochemical conditions are changed (e.g. CMC, Craft-point, etc.). Figure 2 schematically shows the most likely structural configurations and assemblages of surfactants association in an aqueous system (26). Upon addition of oil and a short-chain alcohol, for example, one can convert the oil-in-water micelles into water-in-oil microemulsions. It is therefore possible to induce a transition from one structure to another by changing the physicochemical conditions such as temperature, pH and addition of mono or di-valent cations to the surfactant solution. It should be also noted that the sur-... 

Yang, Y., Zhu, D., Piegat, T.J. and Hua, L. (2007) Enzymatic ketone reduction mapping the substrate profile of a short-chain alcohol dehydrogenase (YMR226c) from Saccharomyces cerevisiae. Tetrahedron Asymmetry, 18 (15), 1799-1803. 

The first situation applies for the short-chain alcohols, acetone, or ether. After their evaporation, the drug remains finely dispersed on or in the skin at 100% concentration. 

Polar neutral organics can be very miscible in water due to their compatibility with the polar water molecules. For example, dipole-dipole interactions such as those interactions between short-chain alcohols and water give rise to essen-... 

Miscible organic solutes modify the solvent properties of the solution to decrease the interfacial tension and give rise to an enhanced solubility of organic chemicals in a phenomenon often called cosolvency . According to theory, a miscible organic chemical such as a short chain alcohol will have the effect of modifying the structure of the water in which it is dissolved. On the macroscopic scale, this will manifest itself as a decrease in the surface tension of the solution [238,246]. 

Reversed-phase chromatography employs a nonpolar stationary phase and a polar aqueous-organic mobile phase. The stationary phase may be a nonpolar ligand, such as an alkyl hydrocarbon, bonded to a support matrix such as microparticulate silica, or it may be a microparticulate polymeric resin such as cross-linked polystyrene-divinylbenzene. The mobile phase is typically a binary mixture of a weak solvent, such as water or an aqueous buffer, and a strong solvent such as acetonitrile or a short-chain alcohol. Retention is modulated by changing the relative proportion of the weak and strong solvents. Additives may be incorporated into the mobile phase to modulate chromatographic selectivity, to suppress undesirable interactions of the analyte with the matrix, or to promote analyte solubility or stability. 

The recent introduction of non-aqueous media extends the applicability of CE. Different selectivity, enhanced efficiency, reduced analysis time, lower Joule heating, and better solubility or stability of some compounds in organic solvent than in water are the main reasons for the success of non-aqueous capillary electrophoresis (NACE). Several solvent properties must be considered in selecting the appropriate separation medium (see Chapter 2) dielectric constant, viscosity, dissociation constant, polarity, autoprotolysis constant, electrical conductivity, volatility, and solvation ability. Commonly used solvents in NACE separations include acetonitrile (ACN) short-chain alcohols such as methanol (MeOH), ethanol (EtOH), isopropanol (i-PrOH) amides [formamide (FA), N-methylformamide (NMF), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA)] and dimethylsulfoxide (DMSO). Since NACE—UV may present a lack of sensitivity due to the strong UV absorbance of some solvents at low wavelengths (e.g., formamides), the on-line coupling of NACE... 

Catalysts described in the literature and in patents contain Pd(OAc)2 and PR3 (R = alkyl and aryl). Short-chained alcohols (Ci to C4) are typically used as nucleophiles (Scheme 3) and at reaction conditions of 120 °C, 50 bar CO and 15 hours, the desired linear (isopropyl-)nonadienoate is formed as the main product with isopropyl alcohol (IPA) as the alcohol component. 

Biodiesel is attracting increasing attention worldwide as blending components or direct replacements for diesel fuel in vehicle engines. Biodiesel typically comprises lower alkyl fatty acid (chain length esters of short-chain alcohols,... 

Further information on the dependence of structure of microemulsions formed on the alcohol chain length was obtained from measurement of self diffusion coefficient of all the constitutents using NMR techniques (29-34). For microemulsions consisting of water, hydrocarbon, an anionic surfactant and a short chain alcohol and C ) the self diffusion... 

Thus, in summary, self diffusion measurements by Lindman et a (29-34) have clearly indicated that the structure of microemulsions depends to a large extent on the chain length of the oosurfactant (alcohol), the surfactant and the type of system. With short chain alcohols (hydrophilic domains and the structure is best described by a bicontinuous solution with easily deformable and flexible interfaces. This picture is consistent with the percolative behaviour observed when the conductivity is measured as a function of water volume fraction (see above). With long chain alcohols (> Cg) on the other hand, well defined "cores" may be distinguished with a more pronounced separation into hydrophobic and hydrophilic regions. 

A microemulsion is defined as a thermodynamically stable and clear isotropic mixture of water-oil-surfactant-cosurfactant (in most systems, it is a mixture of short-chain alcohols). The cosurfactant is the fourth component, which effects the formation of very small aggregates or drops that make the microemulsion almost clear. 

Oil-water mixture is added to a surfactant. To this emulsion, a short-chain alcohol (with four to six carbon atoms) is added continuously until a clear mixture (microemulsion) is obtained. Microemulsions will exhibit very special properties, quite different from those exhibited by ordinary emulsions the microdrops may be considered as large micelles. 

One can displace the film of impurity from the interface by adding a sufficient amount of a short-chain alcohol. The films of short-chain alcohols, are, however, so readily desorbed that they do not greatly in-... 

It is well known that the aqueous phase behavior of surfactants is influenced by, for example, the presence of short-chain alcohols [66,78]. These co-surfactants increase the effective value of the packing parameter [67,79] due to a decrease in the area per head group and therefore favor the formation of structures with a lower curvature. It was found that organic dyes such as thymol blue, dimidiiunbromide and methyl orange that are not soluble in pure supercritical CO2, could be conveniently solubihzed in AOT water-in-C02 reverse microemulsions with 2,2,3,3,4,4,5,5-octafluoro-l-pentanol as a co-surfactant [80]. In a recent report [81] the solubilization capacity of water in a Tx-lOO/cyclohexane/water system was foimd to be influenced by the compressed gases, which worked as a co-surfactant. 

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