Solvent or organic phase

All other grafting systems (single organic solvent, two miscible organic solvents, or organic phase of a mixed solvent system) Branched/crosslinked 96-102... 

Product extraction from large volumes of fermentation broth can be complex, requiring large volumes of organic solvent or solid-phase extraction techniques, which can sometimes greatly reduce or even cancel out the benefits of the biotransformation itself, such as shorter route and environmentally benign conditions. 

In these applications, solvent extraction constitutes an extraction stage during which an organic phase is in contact with an aqueous phase or another immiscible organic phase. The extract is then recovered by distillation or washing with an aqueous or organic phase. 

Solvent extraction Database (SXD) software has been developed by A. Varnek et al.51 Each record of SXD corresponds to one extraction equilibrium and contains 90 fields to store bibliographic information, system descriptions, chemical structures of extractants, and thermodynamic and kinetic data in textual, numerical, and graphical forms. A search can be performed by any field including 2D structure. SXD tools allow the user to compare plots from different records and to select a subset of data according to user-defined constraints (identical metal, content of aqueous or organic phases, etc.). This database, containing about 3,500 records, is available on the INTERNET (http //infochim.u-strasbg.fr/sxd). 

However, applying extraction by solvent to the nuclear field is not an easy task for the solvent that undergoes multiple attacks—chemical, thermal, but especially radiolytic. This multiplicity is reinforced by the biphasic nature of the chemical system and the presence of numerous solutes, be it in aqueous or organic phase. Radiolysis of such a system thus leads to the formation of a multitude of radicals and ionized species (including the reactive species II-, OH-, solvated electrons, H2, or H202), which recombine in molecular products shared between the two phases. 

From the studies published, it appears that it may be possible to improve the radio-lytic stability of an extractant system. Of course, it is difficult to obtain a universal proposal, and the various experimental conditions selected to perform the radiation experiments (nature of the diluents, acidity, and the presence of other solutes either in the aqueous or organic phase) have made the comparison of extractants stability difficult. Nevertheless, systematic tendencies have been summarized in the following section, related to the modification of the extractant alone or related to the composition of the solvent (organic phase). 

Since the release of HCN is a common defense mechanism for plants, the number of available HNLs is large. Depending on the plant family they are isolated from, they can have very different structures some resemble hydrolases or carbox-ypeptidase, while others evolved from oxidoreductases. Although many of the HNLs are not structurally related they all utilize acid-base catalysis. No co-factors need to be added to the reactions nor do any of the HNL metallo-enzymes require metal salts. A further advantage is that many different enzymes are available, R- or S-selective [10]. For virtually every application it is possible to find a stereoselective HNL (Table 5.1). In addition they tend to be stable and can be used in organic solvents or two-phase systems, in particular in emulsions. 

Organic Solvent. The organic phase consists of two or three components reagent, modifier, and solvent. A basic study of possible chemicals for these components dates back to 1960 [5.33],... 

Probably the simplest approach to automate Hquid-liquid extraction is to perform the phase separation by volume. Known volumes of wash or extraction solvent and organic phase are mixed, the phases are allowed to separate, and then only, e.g., 90% of the organic phase is retracted to make sure that no aqueous phase is withdrawn. Obviously, this step can be repeated to optimize recovery. This procedure can be carried out on most synthesizers with essentially no modification of the hardware. 

With water-miscible solvents, the organic phase can be prepared at the desired water activity more conveniently by simple addition of water to the dry solvent. The water concentration required will be significant, and the amount of water added will be much larger than unintentional exchanges with the environment or residual water levels in the dried solvent. The relationship between water concentration and activity will be more or less fixed for a given solvent, and little affected by reasonably low concentrations of reactants. This will not be true for less polar solvents, where direct addition of water rarely gives reproducible hydration or water activity. Table 8-3 gives water contents of various solvents at different water activities. 

Gas phase explosion hazard is present when chlorine is mixed with a fuel in the gas phase. The fuel may be hydrogen, a solvent or organic vapour, ammonia, etc. 

Supported aqueous-phase catalysts (SAPC) can be seen as a special case of adsorption, whereby a water-soluble catalyst dissolved in a very polar solvent is adsorbed on a hydrophilic support forming a water film on the inner surface of the support [30,31]. In the case of supported liquid-phase catalysis (SLPC),the water film on the inner surface is replaced by a solvent of low vapor pressure (e.g.jphthalic acid esters) [2]. The reaction itself takes place in the supportedUq-uid or at the interface of the supported liquid film, or in the gas phase or organic phase when dealing with SLPC or SAPC, respectively. The use of SLPC catalysts is generally restricted to the synthesis of low-boiling compounds. 

Iodine black solid, purple in organic solvents or vapour phase... 

Wang et al. [47] have reported a novel and efficient protocol for ionic liquid supported synthesis of oligosaccharides, which have biological and therapeutic importance. This methodology is remarkable for improved phase separation from organic solvent or aqueous phase. The ionic liquid supported oligosaccharides were... 

An N-methylimidazolium chloride-based ionic support bearing an aldehyde, analogous to the known AMEBA [52] solid support [53] readily dissolves in an ionic liquid solvent such as n-butylimidazolium herafluorophosphate ([BMIM][PF6]). It has been used to prepare a set of diverse sulfonamides and amides according to (Scheme 5.5-34) [39] with isolated yields ranging from 26 to 54% and purities from 55 to 95%, as determined by NMR spectroscopy, comparable to those obtained from solid support chemistry [53]. Reactions were monitored by H PLC. No leakage of the ionically supported substrate into the aqueous or organic phase occurred. 

Systems that are especially amenable to this technique are those involving chemical interactions. Using the process of solvent extraction as a reasonable model, we can alter the value of D of an analyte two ways. First, D for any substance depends on the organic solvent, because Kq will change. Second, the value of D when chemical interaction occurs in either aqueous or organic phase, can change in very dramatic fashion. 

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