Solubilization under mild conditions

Figure 10 shows the sequence of chemical and physical effects leading to coal solubilization under mild conditions. The first step in the conversion involves catalyst-coal contacting a slow rate of contacting may limit the effective reactivity of the catalytic medium. The nature of the... 

Such networks that can be easily solubilized under mild conditions maybe useful as materials. Besides, the possibility to study the residual material after hydrolysis of linear chains may provide more insight into the mechanism of network formation. ... 

Shinn, J. H. Vermeulen, T. "Scanning Electron Microscopy Study of the Solubilization of Coal Under Mild Conditions". Paper submitted for presentation at Scanning Electron Microscopy Symposium, Washington, D.C., April 1979. 

Using dicyclohexyl-18-crown-6 it is possible to dissolve potassium hydroxide in benzene at a concentration which exceeds 0.15 mol dm-3 (Pedersen, 1967). The free OH- has been shown to be an excellent reagent for ester hydrolysis under such conditions. The related solubilization of potassium permanganate in benzene, to yield purple benzene , enables oxidations to be performed in this solvent (Hiraoka, 1982). Thus, it is possible to oxidize a range of alkenes, alcohols, aldehydes, and alkylbenzenes under mild conditions using this solubilized reagent. For example, purple benzene will oxidize many alkenes or alcohols virtually instantaneously at room temperature to yield the corresponding carboxylic acids in near-quantitative yields (Sam Simmons, 1972). 

Acid catalyzed depolymerization of coal with phenol affords a means for dissolution of coal under relatively mild conditions (185°C, ambient pressure). Once dissolved, separation of ash constituents and unreacted char is accomplished by filtration or centrifugation (also under mild conditions). Depolymerized coal recovered as a low ash product from excess phenol could be dissolved in a coal derived solvent and hydrogenated to stable liquids. It might be anticipated that access to hydrogen and contact with the catalyst would be more efficient in the case of the solubilized coal substance than for coal particle slurries. Hydrogenation might proceed more efficiently and with less... 

Protdns that are insoluble in standard aqueous solutions and are solubilized with SDS before subjecUng to electrophoresis may sometimes require spedal treatment For example, Flcofip-galactoridase (mol wt about 120 K) can be readily eluted from Immobilon membranes under mild conditions. However, alactosidase fusion proteins with short segments... 

Acetoxylation of poly(vinyl chloride) can be carried out under homogeneous conditions. Crown ethers, like 18-crown-6, solubilize potassium acetate in mixtures of benzene, tetrahydrofuran, and methyl alcohol to generate unsolvated, strongly nucleophilic naked acetate anions. These react readily with the polymer under mild conditions. Substitutions of the chlorine atoms on the polymeric backbones by anionic species take place by a Sn2 mechanism. The reactions can also proceed by a Sivl mechanism. That, however, requires formations of cationic centers on the backbones in the rate-determining step and substitutions are in competition with elimination reactions. It is conceivable that anionic species may (depending upon basicity) also facilitate... 

Two of the enzymes of the tricarboxylic acid cycle, aconitase and fumarase, catalyze reactions in which water is added reversibly to an unsaturated polycarboxylic acid. Both enzymes exhibit rigid stereospecificity fumarase forms only L-malate from fumarate and forms only fumarate (trans) and not maleate (czs-ethylenedicarboxylic acid), and aconitase reacts with only cis-, not imns-aconitate, and with D-, not L-isocitrate. Citrate is a symmetrical molecule, with no optical isomers, but it will be shown that steric factors also enter into the reaction of this substrate with aconitase. The enzymes of the tricarboxylic acid cycle, in contrast to the glycolytic enzymes, are associated with intracellular granules known as mitochondria. Studies of the individual enzymes have depended to a large extent on the separation of soluble activities from these particles. Aconitase and fumarase are released from the particles very rapidly under mild conditions often in the preparation of cell-free homogenates these activities are largely solubilized, and special care must be taken to demonstrate their origin in mitochondria. 

Naqvi and Joseph [139] studied the kinetics of acet-oxylation of PVC using 18-crown-6 to solubilize KOAc in organic solvents under mild reaction conditions. They concluded that the substitution of chlorines in PVC by acetoxy groups proceeded by an Sn mechanism. 

Liquid-phase oxybromination of phenols, A,A-dialkylanilines, ketones and olefins, under very mild conditions, is reported by Neumann and Assael257 who utilize a heteropolyanion catalyst which was solubilized in organic phase by tetraglyme or crown ether. Exceptionally high para selectivity has been observed in this system in the oxybromination of phenol (equation 36). 

A great variety of chemical reactions can be advantageously carried out in microemulsions [860-862]. In one of the first papers in this field, Menger et al. described the imidazole-catalyzed hydrolysis of 4-nitrophenyl acetate in water/octane microemulsions with AOT as an anionic surfactant [=sodium bis(2-ethyl-l-hexyl)-sulfosuccinate] [864]. The solubilized water, containing the imidazole eatalyst, is confined in spherical pools encased by surfactant molecules, which have only their anionic head groups (-SOb ) immersed in the aqueous droplets. When the ester, dissolved in water-insoluble organic solvents, is added to this water/octane/AOT/imidazole system, it readily undergoes the catalysed hydrolysis under mild reaction conditions (25 °C). 

Because the key to successfully crystallizing a macromolecule often lies in the procedure, means, or solvent used to solubilize it, some careful consideration should be given to this initial step. This is particularly true of membrane, lipophilic, or other proteins which, for one reason or another, are only marginally soluble in water solutions. In addition to mild detergents there are chaotropic agents that can also be employed for the solubilization of proteins. These include such compounds as urea, guanidinium hydrochloride, and relatively innocuous anions such as SCN-, CIOJ, I-, Br", and NO- (HatefI and Hanstein, 1969). These compounds, even at relatively low concentrations, may serve to increase dramatically the solubility of a protein under conditions where it would otherwise be insoluble. 

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