Hydrophobic alcohol

Even in the presence of A1203 powders, the reduction of Pd(II) proceeds as shown in Fig. 5.3. It is clear that the rate of Pd(II) reduction is accelerated by the addition of alcohols. The rate of Pd(II) reduction is strongly dependent on the carbon number of alcohol additives the rate increases in the order of methanol < ethanol < 1-propanol, although the same concentration of alcohol is present in the solution. This observation is due to the fact that the reductants are more efficiently formed from higher hydrophobic alcohols, because higher hydrophobic molecules more efficiently accumulate at the interface of the cavitation bubbles [31]. 

DeTemino, D.M., Hartmeier, W. and Ansorge-Schumacher, M.B. (2005) Entrapment of the alcohol dehydrogenase from Lactobacillus kefir in polyvinyl alcohol for the synthesis of chiral hydrophobic alcohols in organic solvents. Enzyme and Microbial Technology, 36 (1), 3-9. 

W. Kruse, W. Hummel, and U. Kragl, Alcohol-dehydrogenase-catalyzed production of chiral hydrophobic alcohols. 

Production of Enantiomerically Pure Hydrophobic Alcohols Comparison of Different Process Routes and Reactor Configurations 556... 

This chapter describes recent work in our laboratories examining density modification of DNAPLs through a combination of batch non-equilibrium rate measurements and DNAPL displacement experiments in 2D aquifer cells. The objective of this work was to evaluate the applicability of nonionic surfactants as a delivery mechanism for introducing hydrophobic alcohols to convert the DNAPL to an LNAPL prior to mobilizing the NAPL. Three different nonionic surfactants were examined in combination with n-butanol and a range of DNAPLs. Overall, it was found that different surfactants can produce dramatically different rates of alcohol partitioning and density modification. However, for some systems interfacial tension reduction was found to be a problem, leading to unwanted downward... 

The objective of in situ density modification is to use hydrophobic alcohol solutions to reduce the densities of entrapped DNAPLs. For this to work, significant quantities of alcohol must partition into the entrapped DNAPL. This is particularly true for high density chlorinated DNAPLs, such as tetrachloroethylene (PCE). For example, Table 1 shows the calculated percentage of n-butanol that must be present in a NAPL/n-butanol mixture for the density of the mixture to drop below 1 g/mL (calculated assuming constant molar volumes). For PCE, which has a density of 1.623 g/mL, n-butanol (p = 0.81 g/mL) must partition until the final NAPL is more than three quarters alcohol by volume. In order to deliver sufficient alcohol to the entrapped DNAPL, surfactants may be necessary. Surfactants can substantially increase the quantity of alcohol that can be dissolved, allowing more alcohol to be injected into the subsurface. 

A more promising approach for the synthesis of hydrophobic substances with ADHs is published by Kruse et al. [159, 238], They use a continuously operating reactor where the enzyme containing water phase is separated from the hydrophobic substrate-containing organic phase by a membrane. The hydrophobic product is extracted continuously via a hydrophobic membrane into an hexane phase, whereas the coenzyme is regenerated in a separate cycle, that consists of a hydrophilic buffer system. This method decouples advantageously the residence time of the cofactor from the residence time of the substrate. Several hydrophobic alcohols were prepared in this way with (S)-ADH from Rhodococcus erythropolis (Table 16). 

For the production of chiral hydrophobic alcohols, FDH from C. boidinii was combined with an NAD+-dependent alcohol dehydrogenase (ADH) from Rhodo-coccus erythropolis. As a first example for the production of hydrophobic alcohols, an enzyme membrane reactor (EMR) was used for the synthesis enantiomerically pure (S)-1 -phenylpropan-2-ol and some related structures out of their corresponding ketones [42]. 

The correlation equation obtained using the data summarized in Table 10 was 0.938. The modest correlation coefficient may be due to the use of commercial linear primary alcohol ethoxylates from two different manufacturers. Variatiofts in hydrophobe linearity, hydrophobe carbon number distribution about the average value, and EO chain length distribution about the average value were not considered in equation 8. This interpretation is supported by the observation that inclusion of data for three secondary (methyl branched at the alpha position of the hydrophobe) alcohol ethoxylates in the analysis resulted in a decrease of the correlation coefficient to <0.90. 

Most commonly used biocataiytic kinetic resolutions of racemates often provide compounds with high EE, but the maximum theoretical yield of product is only 50%. The reaction mixture contains about a 50 50 mixture of reactant and product that possess only slight differences in physical properties (e.g., a hydrophobic alcohol and its acetate), and thus separation may be very difficult. These issues with kinetic resolutions can be addressed by employing a dynamic kinetic resolution process involving a biocatalyst or biocatalyst with metal-catalyzed in situ racemiza-tion [112-114]. 

Extractants are often used with modifiers (e.g., hydrophobic alcohols, alkylphenols, sterically hindered esters of carboxylic acids, and tributyl phosphate). Modifiers are used for two different reasons first, to increase the solubility of extractants and their complexes and to avoid the formation of the third phase, and second, to modify the extraction properties, i.e., the extraction and stripping abilities. The first option is usually exploited in systems that contain various amines. The second option is associated with hydro-xyoximes and the formation of tailored blends, which optimize the extraction-stripping properties and adjust them to the aqueous feed, i.e., to the acidity and concentration of copper(II). Modifiers that form hydrogen bonds with hydroxyoxime molecules decrease their extraction ability but facilitate back-extraction with acids. Weak hydroxyoxime or j -diketone extractants (e.g., 2-hydroxy-5-alkylbenzo-phenone oxime) can also act as modifiers of strong hydroxyoxime extractants (e.g., salicylaldoxime and its alkyl derivatives). 

TRYCOL Ethoxylated Alcohols are nonionic polyoxyethylene surfactants prepared conunercially by the condensation or addition of ethylene oxide to a hydrophobic compound at the site of an active hydrogen. In this case the active hydrogen is at the hydroxyl group on a hydrophobic alcohol. 

As a consequence of showing that alkylated polyethyleneimines can facilitate aqueous biphasic catalysis, we extended the concept by the preparation of a cross-linked polyethyleneimine assembly that encapsulated a polyoxometalate catalyst, which resulted in the Upophiloselective oxidation of secondary alcohols (Scheme 9.17) [152]. Thus, even though reactions were carried out in water, competitive oxidation of a more hydrophobic alcohol in the presence of a hydrophilic alcohol significantly favored the former. The lipophiloselectivity was proportional to the relative partition coefficient of the substrates. 

Musa, M.M. and Phillips, R.S. (2011) Recent advances in alcohol dehydrogenase-catalyzed asymmetric production of hydrophobic alcohols. Catal. Sci. Technol.,... 

The catalyst activity is influenced by the selective sorption and diffusion of the substrate in the membrane. Generally, substrates that are preferentially adsorbed, and therefore are more concentrated around the catalytic sites, increase the reaction rate on the other hand, diffusion is also an important factor for the catalytic reactions, particularly in dense membranes. Cycloheptanol is the more hydrophobic alcohol in this series and, consequently, can better interact with the PDMS by Van der Waals interactions however, it is also the more stoically constrainted, and the reaction rate is lower than for n-cyclopentanol (Fig. 27.8). 

Comparative fluorescence studies by Harris show that while there is no measurable difference in the mobility of a fluorescent probe in the interior of ethanol-treated membranes of the LS and SS mice, there is a difference in the mobility of a surface probe, with the greater mobility at the surface of the LS mice membranes . While the strains show a difference in their sensitivity to ethanol, they show the same sensitivity to the more hydrophobic alcohol butanol, even though both alcohols elicit the same disordering effects at the interior of the bilayer, albeit at different concentrations. ... 

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