Nonsolvent system

Irimescu and Kato have recently described an interesting example of enzymatic KR in ionic liquids instead of organic solvents (Scheme 7.4) [12]. The resolution with CALB is based on the fact that the reaction equilibrium was shifted toward the amide synthesis by the removal of water under reduced pressure. Nonsolvent systems have been also employed in this enantioselective amidation processes, reacting racemic amines with aliphatic acids. The best reaction conditions for the conversion of acids to amides was observed using CALB at 90 °C under vacuum. Meanwhile, no... 

The interest in catalyst recyclability has led to the development of biphasic catalysts for hydro-boration.22 Derivitization of Wilkinson s catalyst with fluorocarbon ponytails affords [Rh(P (CH2)2(CF2)5CF3 3)3Cl] which catalyzes FIBcat addition to norbornene in a mixture of C6FnCF3 and tetrahydrofuran (TF1F) or toluene (alternatively a nonsolvent system can be used with just the fluorocarbon and norbornene) to give exo-norborneol in 76% yield with a turnover number up to 8,500 (Scheme 4). Mono-, di- and trisubstituted alkenes can all be reacted under these conditions. The catalyst can be readily recycled over three runs with no loss of activity.23... 

The coagulation process can now be considered in perspective of a ternary polymer-solvent-nonsolvent system, A schematic ternary phase diagram, at constant temperature, is shown in Figure 8. The boundaries of the isotropic and narrow biphasic (isotropic-nematic) regions are based on an extension of Flory s theory ( ) to a polymer-solvent-nonsolvent system, due to Russo and Miller (7). These boundaries are calculated for a polymer having an axial ratio of 100, and the following... 

Bll. — Interaction parameters for rubber/nonsolvent systems. J. Polymer Sci. 36, 526 (1959). 

Solvent/nonsolvent system. The solvent must be miscible with the nonsolvent (here an aqueous system). An aprotic polar solvent like N-methyl pyrrolidone (NMP), dimethyl formamide (DMF), dimethyl acetamide (DMAc) or dimethylsulfoxide (DMSO) is preferable for rapid precipitation (instantaneous demixing) upon immersion in the nonsolvent water. As a consequence, a high porosity anisotropic... 

Blnodal-splnodal phase diagram, polymer-solvent-nonsolvent system, 230-32... 

Some groups have reported on their search for less reactive acylating agents, to suppress noncatalyzed chemical acylation and increase product enantiomeric excess. Irimescu and Kato carried out an enantioselective lipase catalyzed acylation of 1 phenylethylamine and 2 phenyl 1 propylamine by reacting the amines with carbox ylic acids in a nonsolvent system or in ionic liquids (Figure 14.9). The reaction equilibrium was shifted toward amide synthesis by the continuous removal of the... 

The physicochemical properties of alkylated polysaccharides have received some attention, and details of the structures and conformations of 0-methylcelluloses, and their interaction in micelle junctions, have been included in a thorough discussion of polysaccharide gels and networks. Information on the polydispersity of samples of partially methylated cellulose may be obtained from column fractionation and by fractional precipitation from a solvent-nonsolvent system, but, for a more complete characterization of polydispersity, fractionation with a series of solvent-nonsolvent systems is necessary. The solubility, in water, of polysaccharides that are mainly methylated may be considerably improved by introduction of a few suitable ionizing groups, for example, by reaction with monochloroacetic acid to introduce carboxymethyl ether groups. The general sorption and diflFusion features of hydrocarbons and other... 

Another coil-rod-coil triblock copolymer 25 with PS as the flexible block and PPE as the rigid segment has been synthesized by Li and Wang. The aggregation behavior of this copolymer was investigated in selective solvents and in solvent/nonsolvent systems. It was clearly demonstrated that the solvent composition greatly affected the polymer s conformation and the aggregate formation. 

Is there a difference in results for the van der Waals and mixing rules The answer is yes, but there is no preponderance of accuracy in one form or another. The van der Waals mixing rules, with two binary parameters, is quite satisfactory for nonassociating, nonsolvating systems. But no mixing rule is adequate for components with hydrogen bonds in dilute solution. The accuracy of the descriptions of excess volume was uneven, with no apparent pattern of success or failure. 

One of the main variables in the immersion precipitation process is the choice of the solvent/nonsolvent system. In order to prepare a membrane from a polymer by phase inversion the polymer must be soluble. Although one or more solvents may be suitable for the chosen polymer, the solvent and nonsolvent must be completely miscible. Water is frequently used as a nonsolvent but other nonsolvents can also be used. Some solvents for cellulose acetate and polysulfone which are miscible with water are listed in table III.6. The solubility of these organic solvents with water must be considered further. As described in the previous section, the miscibility of components of all kind is determined by the free enthalpy of mixing... 

ACPS), have also been used to fabricate microporous membrane [24-29], However, among these techniques, TIPS and IP are the two most commonly employed methods in the fabrication of polymeric membranes including fluoropolymer membranes. One of the main difficulties that limit the successful casting of phase inversion membranes is the lack of a predictable and systematic method in the selection of solvent and nonsolvent systems [30],... 

GA Ogawa, T. and Hoshino, S., Cloud points in isotactic polypropylene-solvent-nonsolvent systems (Jap.), Kobunshi Kagaku, 28, 348, 1971. 

WAN Wang, D., Li, K., and Teo, W.K., Phase separation in polyetherimide/solvent/ nonsolvent systems and membrane formation, J. Appl. Polym. Sci., 71, 1789, 1999. 

SAX Saxena, R. and Caneba, G.T., Studies of spinodal decomposition in a ternary polymer-solvent-nonsolvent system, Polym. Eng. Sci., 42, 1019, 2002. 

A. Filimon, E. Avram, and S. loan, Structure-rheology relationship in complex quaternized polysulfones/solvent/nonsolvent systems. Polym. Bull. 70,1835-1851 (2013). 

In the previous chapters of this book we have dealt mainly with solvable problems. The models could be solved either because they lack interactions (e.g., ideal gases) or because the interactions took place between a small number of particles (Chapter 3) or because the system itself was simple (Chapter 4). From this chapter through the rest of the book we shall be dealing with nonsolvable systems. Liquids, even the simplest ones consisting of hard-sphere particles, pose very difficult theoretical problems. The main difficulty is contained in the configurational partition function, which for simple particles has the form... 

Wiimik FM, Ringsdorf H, Venzmer J (1990) Methanol water as a co-nonsolvent system for poly(n-isopropylacrylamide). Macromolecules 23(8) 2415-2416. doi 10.1021/ma00210a048... 

MOR Morimoto, S. and Ohtani, N., Phase separation enthalpies of polymer solids in ternary polymer-solvent-nonsolvent systems (Jap.), Kenkyu Hokoku Seni Kobunshi Zairyo Kenkyushu, 119, 35, 1979. 

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