Solvent capability

Solvent Extraction. With solvent extraction, organics are separated from a waste by mixing the waste with a solvent capable of dissolving or extracting the organics. The extraction process can have multiple stages and be operated where the solvent and waste pass concurrently or countercurrenfly. 

T-Jumps can also be produced by microwave heating and by laser pulse absorption. These methods remove the restriction to low-resistance solvents any solvent capable of absorbing energy of the applied frequency may be used. The heating time can be extremely short with laser heating. ... 

A similar effect is produced by cocrystallization with protic solvents capable of forming a hydrogen bond-stabilized environment. Thus, dihydropyrimidine 47 (R = R = aryl,R = R = COOR, R = H) cocrystallizes with water (1 1) exclusively as the 1,6 tautomer (98T9837). 2,4,6,6-Tetraphenyldihydropyrimidine 47 (R = R = R = R = Ph, R = H) exists as the 1,6 tautomer in its solvate with... 

It was found that the first step was rate determining. When, moreover, the reaction was run with the same reaction-temperature profiles under both conventional (oil) and microwave (monomode cavity) conditions, different distributions of the intermediate (1) and final (2) products were obtained (Tab. 5.10). Indeed, the product distribution was strongly affected by microwaves when the reaction was run at 85 °C rather than 110 °C, and addition of a small amount of a polar or nonpolar solvent also affected the product distribution. In this work two solvents capable of extensive coupling (i.e. ethanol) and not coupling (i.e. cyclohexane) with microwaves were used. Addition of ethanol strongly shifted the product distribution towards the final product (2), whereas addition of cyclohexane resulted in much lower yield of 2 [34]. 

The same effect is typical of the reactions of alkoxyl radicals with phenols, that is, these reactions are much slower in solvents capable of forming hydrogen bonds with O—H and N—H groups [50]. MacFaul et al. [50] proposed a universal scale for correlating the reactivities of phenols and the hydrogen-bonding abilities of solvents. 

In the RESS method, the solute of interest is solubilized in a supercritical fluid, which is then rapidly expanded through a nozzle. As the fluid expands, it loses its solvent capabilities and the solute precipitates out. While this technique has the advantage of not using any organic solvent, it is restricted by the generally poor solubility of most polymers in supercritical fluids. Indeed, polymers generally have to be below 10,000 MW in order to be eligible for this method of particle production [126]. 

The tuneable solvent capability of SCCO2 offers the potential for a subtle control of reactions in order to achieve higher selectivities and improved reaction rates. Furthermore, the separation of extractives or, in the case of a synthesis, of reactants, products, and catalysts by simple decompression could be facilitated. The low solubility of many metal complexes and catalysts usually is an obstacle to their exploitation in SCCO2-based processes. For instance, the solubility of a homogeneous catalyst needs to be sufficiently high to ensure participation of all active metal centers during a catalyzed reaction. In particular for reactions, solubility properties are difficult to predict, because the component composition is continuously changed with conversion. 

The solvent is the reaction medium and as such, by solvating the ground and activated states, will influence the energetics of the activation process. In addition it acts as a nucleophile in the reaction path represented by Ati. A large value of relative to Atj is observed in solvents capable of coordinating strongly to the metal so that generally the order... 

Most linear celluloses may be dissolved in solvents capable of breaking the strong hydrogen bonds. These solutions include aqueous solutions of inorganic acids, calcium thiocyanate, zinc chloride, lithium chloride, ammonium hydroxide, iron sodium tartrate, and cadmium or copper ammonium hydroxide (Schweitzer s reagent). The product precipitated by the addition of a nonsolvent to these solutions is a highly amorphous, regenerated cellulose. 

The effect of the medium on the rates and routes of liquid-phase oxidation reactions was investigated. The rate constants for chain propagation and termination upon dilution of methyl ethyl ketone with a nonpolar solvent—benzene— were shown to be consistent with the Kirkwood equation relating the constants for bimolecular reactions with the dielectric constant of the medium. The effect of solvents capable of forming hydrogen bonds with peroxy radicals appears to be more complicated. The rate constants for chain propagation and termination in aqueous methyl ethyl ketone solutions appear to be lower because of the lower reactivity of solvated R02. .. HOH radicals than of free RO radicals. The routes of oxidation reactions are a function of the competition between two R02 reaction routes. In the presence of water the reaction selectivity markedly increases, and acetic acid becomes the only oxidation product. 

As compared to conventional organic solvents, ILs are much more complex solvents, capable of undergoing many types of interactions. Therefore, a single polarity term fails to describe the type and magnitude of individual interactions that they make. 

Polybrominated Biphenyls. The photolytic degradation of PBBs in solution has been the subject of several studies. Available data in the literature indicate that brominated biphenyls photodegrade by reduction in solvents capable of proton transfer with the formation of lower brominated biphenyls. For example, the irradiation of FireMaster BP-6 and 2,2, 4,4, 5,5 -hexabromobiphenyl in methanol at wavelengths >286 nm produced mainly penta- and tetrabromobiphenyl (Ruzo and Zabik 1975). FireMaster BP-6 photolyzed7 times faster than its chlorinated counterpart, 2,2, 4,4, 5,5 -hexachloro-biphenyl (Ruzo and Zabik 1975). Although an earlier study tentatively identified dimethoxy tetrabromobiphenyl as a photolysis product of FireMaster BP-6 (Ruzo and Zabik 1975), later work did not detect this compound (Ruzo et al. 1976). Earlier studies indicated that the debromination usually occurs with the stepwise preferential loss of bromine from the ortho and para positions of the biphenyl ring (i.e., 2, 2, 6, and 6 positions) (De Kok et al. 1977 Ruzo and Zabik 1975 Ruzo et al. 1976 Trotter 1977). Thus, the photolysis of 2,2, 4,4, 5,5 -hexachlorobiphenyl, the major component of FireMaster BP-6, would be expected to produce 23, 4,4, 5-pentabromobiphenyl and subsequently... 

Supercritical fluid chromatography (SFC) is a relatively recently developed chromatographic technique. Because of its ability to deal with compounds that are either polar or of high molecular weight, much attention has recently focused on applications of SFC to the analysis of different analytes using a variety of fluids or fluid mixtures to provide differing solvent capabilities and select vities. As a result there is a large amount of research currently underway both in SFC method development and in hardware development. 

Extraction of nitrofuran antibacterials from edible animal products should render the bound residues soluble, remove most if not all of tire proteins, and provide high yields for ah analytes. Sample extraction/deproteinization is usually accomplished with organic solvents capable to free the noncovalently bound residues from the endogenous macromolecules. Organic solvents including acetoni-... 

Other substances exert a similar influence on the stability of PETN, for example solvents capable of lowering its melting temperature. 

Ternary/quatemary versus binary solvent capabilities are instrument dependent. 

Addition of aqueous potassium hydroxide solution to the organic solvent would be expected to provide ample water for reaction but would also decrease the boiling point of the system. The decrease in solvent efficiency of those systems that were aqueous by design might then be attributed to the decreased reaction temperature. To support or disprove this hypothesis, additional experiments were made to ascertain the solvent capability of the studied systems at the same temperature. 

Figure 2. Relationship of solvent capability to temperature (boiling point of system)...

C. The results (Figure 3) show no significant difference in solvent capability at constant temperature, further indicating that temperature and not solvent is the significant variable. 

In the presence of a solvent capable of reacting with a carbene center, products other than 2-fluoropyridines were formed. Indeed, these can become the major reaction products (87TL2705 89JOC1726), but not all products can be explained in terms of the carbene mechanism since in the 6-chloro-2-fluoropyridinium triflate (25 R = 6-C1, X = S03CF3) it is obvious that chloro is being replaced by fluoride (89JOC1726). 

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