Surfactants in organic solvents

Usually, activities of enzymes (hydrogenases included) are investigated in solutions with water as the solvent. However, enhancement of enzyme activity is sometimes described for non-aqueous or water-limiting surroundings, particular for hydrophobic (or oily) substrates. Ternary phase systems such as water-in-oil microemulsions are useful tools for investigations in this field. Microemulsions are prepared by dispersion of small amounts of water and surfactant in organic solvents. In these systems, small droplets of water (l-50nm in diameter) are surrounded by a monolayer of surfactant molecules (Fig. 9.15). The water pool inside the so-called reverse micelle represents a combination of properties of aqueous and non-aqueous environments. Enzymes entrapped inside reverse micelles depend in their catalytic activity on the size of the micelle, i.e. the water content of the system (at constant surfactant concentrations). 

Martinek, K., Levashov, A. V, Klyachko, N. L., Pantin, V. L, and Berezin, I. V. (1981). The principles of enzyme stabilization. 6. Catalysis by water-soluble enzymes entrapped into reversed micelles of surfactants in organic solvents. Biochem. 

An emulsifier system must cause the concentrate to disperse spontaneously into small, stable droplets when mixed with water. To accomplish this, the surfactant system must have a most favorable solubility relationship a proper balance between oil and water solubility or, in other words, a favorable hydrophile-lipophile balance in solubility. This balance in solubility is frequently referred to as HLB and was first described by Griffin (6). However, the HLB system is based on the structure of a surfactant molecule and, therefore, predicts the behavior of a single molecule. It does not take into account tr 3 fact that many surfactants form micelles in organic solutions. If a micelle is formed, its HLB may have no relationship to the HLB of the monomer unit. Therefore, to select an emulsifier well, we will need a better understanding of the behavior of surfactants in organic solvents. 

Extractions Utilizing Surfactants in Organic Solvents. The use of organic solvents containing surfactants in extractive metallurgy has probably been the most prevalent application of surfactants in chemical separations (1.5.240-262). Table XIII summarizes some of the... 

Protein (enzyme) incorporation into reverse micelles of surfactant in organic solvents may be achieved by one of the following methods. 

Wang D, Hao J. Self-assembly fibrillar network gels of simple surfactants in organic solvents. Langmuir. 27(5) (2011) 1713-1717. 

Kabanov, A.V., Levashov, A.V., Klyachko, N.L., Namyotkin, S.N., Pshezhetsky, A.V. 1988. Enzymes entrapped in reversed micelles of surfactants in organic solvents A theoretical treatment of the catalytic activity regulation. J. Theor. Biol. 133,... 

Another term, the critical solution temperature (CST), was introduced to designate the temperature beyond which the solubility of nonionic surfactants in organic solvents increases markedly, as marked by an inflection in the solubility curve. Mazer and Benedek used the critical micellar temperature (CMT) to refer to the phase boundary between a hydrated solid phase and a micellar phase." The CMT value was taken as the midpoint of the temperature range over which the hydrated solid phase clarified on slow warming with vigorous shaking. 

PMs are orange-colored, with an absorption maximum at 488 nm (Fig. 9.6). The absorption characteristics and chemiluminescence activities of those compounds are shown in Table 9.4. All PMs are brightly fluorescent in yellow in organic solvents and also in aqueous solutions containing a surfactant (emission maxima 520-530 nm). The chemiluminescence spectra of PMs are significantly affected by the... 

Since the compartmentalization occurs as a result of microphase separation of an amphiphilic polyelectrolyte in aqueous solution, an aqueous system is the only possible object of study. This limitation is a disadvantage from a practical point of view. Our recent studies, however, have shown that this disadvantage can be overcome with a molecular composite of an amphiphilic polyelectrolyte with a surfactant molecule [129], This composite was dissolvable in organic solvents and dopable in polymer film, and the microphase structure was found to remain unchaged in the composite. This finding is important, because it has made it possible to extend the study on photo-systems involving the chromophore compartmentalization to organic solutions and polymer solid systems. 

The chemical properties of the alkylarylsulfonates are used in its analytical determination. As anions, LAS and other anionic surfactants react with large cations to salts, which are soluble in organic solvents (e.g., CHC13). By analysis it can be seen that cations such as Hyamine 1622 (25) and methylene blue, which rearrange with LAS to complex (26), are widely spread. These reactions are the basis for the so-called two-phase titration, an extensively used method... 

Alkanolamides from fatty acids are environmentally benign surfactants useful in a wide range of applications. It was found that most lipases catalyze both amidation and the esterification of alkanolamides however, normally the predominant final products are the corresponding amides, via amidation, and also by esterification and subsequent migration [15]. Recently, an interesting example for the production of novel hydroxyl-ated fatty amides in organic solvents has been carried out by Kuo et cd. [16]. 

Recent development of the use of reversed micelles (aqueous surfactant aggregates in organic solvents) to solubilize significant quantities of nonpolar materials within their polar cores can be exploited in the development of new concepts for the continuous selective concentration and recovery of heavy metal ions from dilute aqueous streams. The ability of reversed micelle solutions to extract proteins and amino acids selectively from aqueous media has been recently demonstrated the results indicate that strong electrostatic interactions are the primary basis for selectivity. The high charge-to-surface ratio of the valuable heavy metal ions suggests that they too should be extractable from dilute aqueous solutions. 

The residue is removed from the leaf surface by shaking the leaf punch sample in an aqueous surfactant solution. This allows for removal of test substance residue from the leaf surface. It does not remove residue absorbed on the plant matrix that extraction and maceration in organic solvents would release. Generally, the extraction with aqueous surfactant is performed using a mechanical shaker for a 10-min interval and is repeated to increase transfer efficiency. 

The reactive crystallization has some peculiar characteristics like insoluble product, initiation of reaction by change in pH and conductivity. In this case the solution becomes saturated and eventually supersaturated with respect to reactant nucleation [30], The ultrasound assisted decomposition precursors includes dissolving metal organic precursors in organic solvents/water with the assistance of surfactants leads to monodisperse and reduced metal/metal oxide nanoparticles. 

Enzyme activity for the polymerization of lactones was improved by the immobilization on Celite [93]. Immobilized lipase PF adsorbed on a Celite showed much higher catalytic activity than that before the immobilization. The catalytic activity was further enhanced by the addition of a sugar or poly(ethylene glycol) in the immobilization. Surfactant-coated lipase efficiently polymerized the ring-opening polymerization of lactones in organic solvents [94]. 

Mannich and related readions provide one of the most fundamental and useful methods for the synthesis of p-amino carbonyl compounds, which constitute various pharmaceuticals, natural products, and versatile synthetic intermediates.1271 Conventional protocols for three-component Mannich-type readions of aldehydes, amines, and ketones in organic solvents indude some severe side reactions and have some substrate limitations, espedally for enolizable aliphatic aldehydes. The dired synthesis of P-amino ketones from aldehydes, amines, and silyl enolates under mild conditions is desirable from a synthetic point of view. Our working hypothesis was that aldehydes could read with amines in a hydro-phobic reaction fidd created in water in the presence of a catalytic amount of a metal triflate and a surfactant to produce imines, which could then read with hydrophobic silyl enolates. 

All the above reactions of PVC were performed homogeneously in DA-solvents such as HMPA, DMF and dimethylsulfoxide (DMSO). For the practical modification of PVC, the reaction must be conducted under more commercial conditions as in slurry water. As mentioned before, azidation of PVC did not occur in water. However, the reaction proceeded feasibly in water by addition of some cationic surfactant to give, e.g. 8-20% (DS) of azidated PVC at 80°C by use of tetra-n-butyl ammonium chloride (1 ). The use of cationic surfactant was also effective in organic solvents and attracted increased attention as the conception of "phase transfer catalyst" in organic chemistry developed. 

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