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Cosolvents enhanced

Hansen, T.V., Waagen, V., Partali, V., Anthonsen, H.W. and Anthonsen, T. (1995) Cosolvent enhancement of enantioselectivity in lipase-catalysed hydrolysis of racemic esters. A process for production of homochiral C-3 building blocks using lipase B from Candida antarctica. Tetrahedron Asymmetry, 6, 499-504. [Pg.60]

As with many of the enhancers described above, a synergistic effect for terpene efficacy has also been shown when PG was used as the vehicle [54] with this cosolvent, enhancer activities for carveol, carvone, pulegone, and 18 cineole rose approximately fourfold, explained by improved partitioning of the terpene into the stratum corneum. Enhancement using terpenes in PG has recently been revisited for haloperidol delivery through human skin [55,56],... [Pg.245]

The solubility data can be qualitatively understood as follows. In the very water-rich mixtures, both the apolar solute and the cosolvent enhance water-water interactions (Ben-Naim, 1965) so that... [Pg.306]

Carbon dioxide is the supercritical solvent that is used most in homogeneous catalytic reactions. In addition to being environmentally acceptable (nontoxic, nonflammable), carbon dioxide is inert in most reactions, is inexpensive, and is available in large quantities. Its critical temperature is near ambient. Supercritical carbon dioxide dissolves nonpolar, nonionic, and low molecular mass compounds. However, addition of cosolvents enhances the solubility of many compounds in supercritical carbon dioxide. [Pg.2919]

Overall, it appears that PAH desorption in an electrokinetic cell could be enhanced by use of n-butylamine or ethanol as a cosolvent, but actual removal efficiencies are very low. Therefore, further study is required to achieve high removal efficiencies in cosolvent-enhanced systems. Moreover, the application of cosolvent requires care because cosolvents are flammable and explosive, which could pose particular dangers in electrokinetic applications (Saichek and Reddy, 2005a). [Pg.209]

Li A, Cheung KA, Reddy KR (2000). Cosolvent-enhanced electrokinetic remediation of soils contaminated with phenanthrene. Journal of Environmental Engineering-ASCE 126(6) 527-533. [Pg.215]

Maturi K, Reddy KR (2008). Cosolvent-enhanced desorption and transport of heavy metals and organic contaminants in soils during electrokinetic remediation. Water Air and Soil Pollution 189(1-4) 199-211. [Pg.215]

L4 COSOLVENT-ENHANCED ELECTROKINETIC REMEDIATION OE CHLORINATED PESTICIDES... [Pg.246]

Cosolvent-enhanced electrokinetic remediation of chlorinated pesticides has yet to be explored. Few studies have shown enhancements in the transport of polycyclic aromatic hydrocarbons (PAHs) when cosolvents were used (Maturi and Reddy, 2008 Reddy and Saichek, 2003). The potential success of cosolvents depends on their ability to mobilize the HOCs and to increase the EOF. It was shown that 10% n-butylamine generated the greatest EOF, followed by 20% n-butylamine and water (Maturi and Reddy, 2008). The sorption of solvents to the soil matrix may not be as high as the surfactants, which cause a better solubilization with the same amount of electro-osmotic transport. [Pg.246]

Methanol is more soluble in aromatic than paraffinic hydrocarbons. Thus varying gasoline compositions can affect fuel blends. At room temperature, the solubiUty of methanol in gasoline is very limited in the presence of water. Generally, cosolvents are added to methanol—gasoline blends to enhance water tolerance. Methanol is practically insoluble in diesel fuel. [Pg.87]

Evaporation Retardants. Small molecule solvents that make up the most effective paint removers also have high vapor pressure and evaporate easily, sometimes before the remover has time to penetrate the finish. Low vapor pressure cosolvents are added to help reduce evaporation. The best approach has been to add a low melting point paraffin wax (mp = 46-57° C) to the paint remover formulation. When evaporation occurs the solvent is chilled and the wax is shocked-out forming a film on the surface of the remover that acts as a barrier to evaporation (5,6). The addition of certain esters enhances the effectiveness of the wax film. It is important not to break the wax film with excessive bmshing or scraping until the remover has penetrated and lifted the finish from the substrate. Likewise, it is important that the remover be used at warm temperatures, since at cool temperatures the wax film may not form, or if it does it will be brittle and fracture. Rapid evaporation occurs when the wax film is absent or broken. [Pg.550]

Some hquid defoamers are preemulsified relatives of paste defoamers. In addition to the fatty components mentioned above, kerosene [8008-20-6] or an organic cosolvent such as 2-propanol have been used to enhance stabiUty of the oil—water emulsion and the solubiUty of the defoamer s active ingredients. These cosolvents are used less frequently as concerns increase about volatile organic emissions (VOCs) from the paper machine. Additionally, the use of ultrapure mineral oil in defoamers has become commonplace. Concern about the creation of 2,3,7,8-tetrachlorodibenzodioxin (TCDD) and 2,3,7,8-tetrachlorodibenzofuran (TCDF) in the pulping process has led to the discovery of unchlorinated precursor molecules, especially in recycled mineral oil and other organic cosolvents used in defoamer formulations (28). In 1995 the mineral oil that is used is essentially free of dibenzodioxin and dibenzofuran. In addition, owing to both the concern about these oils and the fluctuating cost of raw materials, the trend in paper machine defoamers is toward water-based defoamers (29). [Pg.16]

Pesticide Solvent. The majority of organic fungicides, insecticides, and herbicides (qv) are soluble in DMSO, including such difficult-to-solvate materials as the substituted ureas and carbamates (see Fungicides, agricultural Insect control technology Pesticides). Dimethyl sulfoxide forms cosolvent systems of enhanced solubiUty properties with many solvents (109). [Pg.112]

Selectivity Enhancement by Addition of Water-Miscible Organic Cosolvents... [Pg.5]

Several other examples have been reported in the literature and most of them have been already revievred (see, for instance, [11]). Hovrever, it must be mentioned that, of course, the selectivity enhancement via addition of vater-misdble organic cosolvents may not be taken for granted, as sometimes this approach may be unsuccessfij] [11a]. [Pg.7]

Soluble organic solvents have often been used as cosolvents to solubilize miscible organic substrates. Since organic compounds including solvents are possibly incorporated inside of the enzyme, they may affect the stereoselectivity of enzymatic reactions. For example, dimethyl sulfoxide (DMSO) (10%) enhance not only chemical yield but also enantioselectivity of yeast reduction. Thus, the poor yield of 23% with 80% ee was increased to 65% yield with >99% ee (Figure 8.20) [17]. [Pg.209]

A cosolvent used as a miscible additive to CO2 changed the properties of the supercritical gas phase. The addition of a cosolvent resulted in increased viscosity and density of the gas mixture and enhanced extraction of the oil compounds into the C02-rich phase. Gas phase properties were measured in an equilibrium cell with a capillary viscometer and a high-pressure densitometer. Cosolvent miscibility with CO2, brine solubility, cosolvent volatility, and relative quantity of the cosolvent partitioning into the oil phase are factors that must be considered for the successful application of cosolvents. The results indicate that lower-molecular-weight additives, such as propane, are the most effective cosolvents to increase oil recovery [1472]. [Pg.213]

The effect of the steric bulk of the hydride reducing agent has been examined in the case of 3-benzyloxy-2-butanone.135 The ratio of chelation-controlled product increased with the steric bulk of the reductant. This is presumably due to amplification of the steric effect of the methyl group in the chelated TS as the reductant becomes more sterically demanding. In these reactions, the degree of chelation control was also enhanced by use of CH2C12 as a cosolvent. [Pg.413]

Density functional theory study of aqueous-phase rate acceleration and endo/exo selectivity of the butadiene and acrolein Diels-Alder reaction72 shows that approximately 50% of the rate acceleration and endo/exo selectivity is attributed to hydrogen bonding and the remainder to bulk-phase effects, including enforced hydrophobic interactions and cosolvent effects. This appears to be supported by the experimental results of Engberts where a pseudothermodynamic analysis of the rate acceleration in water relative to 1-propanol and 1-propanol-water mixtures indicates that hydrogen-bond stabilization of the polarized activated complex and the decrease of the hydrophobic surface area of the reactants during the activation process are the two main causes of the rate enhancement in water.13... [Pg.391]


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See also in sourсe #XX -- [ Pg.209 ]




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