Lipophiles organic solvents

Extraction of protein from aqueous solution by surfactant-containing lipophilic organic solvent (phase transfer method, or equivalently, w/o-ME-based liquid-liquid extracting, LEE). 

The free bases are soluble in lipophilic organic solvents, like chloroform. The different solubility for bases and salts is used for isolation and purification. Alkaloids are generally colourless solid materials. Some alkaloids that do not contain oxygen, like coniine, nicotine and sparteine, are liquid, and berberine and chelidonine are intensely yellow. Several alkaloids, e.g. strychnine and quinine, have a very bitter taste. Alkaloids give precipitates with heavy metals like mercury and bismuth. DragendorfPs reagent is used to show the presence of alkaloids. 

Perhaps structurally the most simple primary amide gelators, 3,4,5-tris-(alkoxy) benzamides 1 and 2 (Fig. 1), have been prepared by amidation of tris(alkoxy)benzoic acids and shown to gel both polar (MeOH, EtOH, DMF) and highly lipophilic organic solvents (n-octane, w-decane, toluene) at minimal gelation concentrations (mgc) lower than 2.5 wt % [5]. The gel aggregates can be embedded into cross-linked polymer matrices using monomer/cross-linker mixtures as organic solvents. 

Polymerization, which requires the presence of water, can also be avoided if the reaction is performed in a lipophilic organic solvent such as chloroform (Sect. 3.1) [1133]. 

Numerous inorganic and organic materials have been used as carriers activated charcoal [375], alumina [376], silica [377, 378], diatomaceous earth (Celite) [165, 379], cellulose [380], controUed-pore glass, and synthetic resins [381]. In contrast to the majority of enzymes, which preferably adsorb to materials having a polar surface, lipases are better adsorbed onto lipophilic carriers due to their peculiar physicochemical character (Sect. 2.1.3.2) [72, 382-385]. Adsorption is the method of choice when enzymes are used in lipophilic organic solvents, where desorptiOTi cannot occur due to their insolubility in these media. 

Surface-Modified Enzymes. Enzymes acting in nearly anhydrous organic solvents always give rise to heterogeneous systems (Sect. 3.1). In order to turn them into homogeneous systems, which can be controlled more easily, proteins can be modified in order to make them soluble in lipophilic organic solvents. This can be readily achieved by covalent attachment of the amphipathic polymer polyethylene glycol (PEG) onto the surface of enzymes [460]. The pros and cons of PEG-modified enzymes are as follows [461, 462] ... 

Bioimprinting. Bearing in mind that conformational changes are impeded in lipophilic organic solvents - in other words, the structure of the enzymes appears to be frozen in such media but remains flexible in water - the specificity of biocatalysts may be altered in the following way (Fig. 3.9) [488, 489]. 

Emulsifiers. Removing the remover is just as important as removing the finish. For water rinse removers, a detergent that is compatible with the remover formula must be selected. Many organic solvents used in removers are not water soluble, so emulsifiers are often added (see Emulsions). Anionic types such as alkyl aryl sulfonates or tolyl fatty acid salts are used. In other appHcations, nonionic surfactants are preferred and hydrophilic—lipophilic balance is an important consideration. 

Polyethers are usually found in both the filtrate and the mycelial fraction, but in high yielding fermentations they are mosdy in the mycelium because of their low water-solubiUty (162). The high lipophilicity of both the free acid and the salt forms of the polyether antibiotics lends these compounds to efficient organic solvent extraction and chromatography (qv) on adsorbents such as siUca gel and alumina. Many of the production procedures utilize the separation of the mycelium followed by extraction using solvents such as methanol or acetone. A number of the polyethers can be readily crystallized, either as the free acid or as the sodium or potassium salt, after only minimal purification. 

Stability. Avermectins are highly lipophilic substances and dissolve in most organic solvents such as chloroform, methylene chloride, acetone, alcohols, toluene, cyclohexane, dimethylformamide, dimethyl sulfoxide, and tetrahydrofiiran. Thek solubiUty in water is correspondingly low, only 0.006-0.009 ppm (= mg/L). 

For practical appHcation in mixtures of water—organic solvent, only ammonium and phosphonium salts containing 15 or more C atoms are sufficiently lipophilic. In empirical catalyst comparisons crown ethers (hexaoxacyclooctodecanes) (1)—(3) were often as effective as the best onium salts. 

The lipophilicity of the TRISPHAT anion 8 also confers to its salts an affinity for organic solvents and, once dissolved, the ion pairs do not partition in aqueous layers. This rather uncommon property was used by Lacour s group to develop a simple and practical resolution procedure of chiral cationic coordination complexes by asymmetric extraction [134,135]. Selectivity ratios as high as 35 1 were measured for the enantiomers of ruthenium(II) trisdiimine complexes, demonstrating without ambiguity the efficiency of the resolution procedure [134]. 

The microgels could be conveniently isolated by precipitation as white powders, readily redispersable in many different organic solvents such as dialkylamides, nitriles, dichloromethane, acetone and THF. Further to this, the DMAA-based microgels exhibited a rather amphiphilic character and were also soluble in water and in alcohols such as methanol or ethanol in contrast, their counterparts based on MMA turned out to be more lipophilic and therefore insoluble in water and alcohols but soluble in organic solvents of low polarity such as toluene. 

Today, lipophilicity can be determined in many systems that are classified by the characteristics of the nonaqueous phase. When the second phase is an organic solvent (e.g. n-octanol), the system is isotropic, when the second phase is a suspension (e.g. liposomes), it is anisotropic, and when the second phase is a stationary phase in liquid chromatography, it is an anisotropic chromatographic system [6]. Here, we discuss the main aspects of isotropic and anisotropic lipophilicity and their biological relevance the chromatographic approaches are investigated in the following chapter by Martel et al. 

The pKa of basic compounds as well as the buffered mobile phase were influenced by the organic solvent and depended on its proportion in the soluhon. The results indicated that the stationary phases and mobile phases studied were not suitably optimized for the estimation of lipophilicity of basic compounds. 

The lipophilicity of a solute affects its permeability in lipid bilayers. Lipophilicity is usually expressed in terms of its partitioning between water and an organic solvent, such as olive oil [95], oleyl alcohol [96], ether [97], or octanol [98]. Partition coefficient (PC) of a compound is expressed as its concentration ratio between organic medium and water at equilibrium ... 

Catalysis in Transacylation Reactions. The principal objective of the study was to evaluate 4 as an effective organic soluble lipophilic catalyst for transacylation reactions of carboxylic and phosphoric acid derivatives in aqueous and two-phase aqueous-organic solvent media. Indeed 4 catalyzes the conversion of benzoyl chloride to benzoic anhydride in well-stirred suspensions of CH2CI2 and 1.0 M aqueous NaHCC>3 (Equations 1-3). The results are summarized in Table 1 where yields of isolated acid, anhydride and recovered acid chloride are reported. The reaction is believed to involve formation of the poly(benzoyloxypyridinium) ion intermediate (5) in the organic phase (Equation 1) and 5 then quickly reacts with bicarbonate ion and/or hydroxide ion at the interphase to form benzoate ion (Equation 2 and 3). Apparently most of the benzoate ion is trapped by additional 5 in the organic layer or at the interphase to produce benzoic anhydride (Equation 4), an example of normal phase-... 

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