Solvents, organic, avoidance

Additionally, the sequestering ability of polyphosphoric acid and phosphonic acid derivatives as well is a valuable property for their use as dispersants. The main task of dispersants is to suspend solid particles in water or organic solvents and avoid their coalescence and precipitation. This complex plays an important role in many processes and as a result dispersants are used in many technical fields. 

The oxidation of alcohols is an important reaction in organic chemistry. While this transformation is traditionally performed in organic solvents, the use of aqueous orgarric solutions has just recently become a field of intense study (1-6). The effect of water on transition metal-catalyzed reactions, however, remains widely unexplored as most of these reactions require dry organic solvents to avoid decomposition of the transition metal catalyst, of water sensitive reagents, and/or intermediates by a nucleophilic attack of water (1). Comparative studies focusing on the effect of water as a co-solvent on the catalyst and the proceedings of a reaction are therefore rare (7). 

More direct and successful methods for the preparation of non-aqueous metal sols are desirable. Especially valuable would be a method that avoids the metal salt reduction step (and thus avoids contamination by other reagents), avoids electrical discharge methods which decompose organic solvents, and avoids macromolecule stabilization. Such a method would provide pure, non-aqueous metal colloids and should make efficient use of precious metals employed. Such colloids would be valuable technologically in many ways. They would also be valuable to study so that more could be learned about particle stabilization mechanisms in non-aqueous media, of which little is known at the present time. 

An also frequently occurring problem may be the low solubility of test compounds in aqueous solvents. Organic cosolvents, such as DMSO or ethanol can be used however, due to limited cell viability, final concentrations above 1 % have to be avoided. 

The manufacturing process ofPCN involves different methods (1) Solution method in which clay and polymer are dissolved in a polar organic solvent to avoid coiling of the polymer in the... 

Iin and co-workers [40] have developed a so-called micro-aqueous organic reaction system. In contrast to former preparations of almond meal, the almond kernels are soaked in water prior to grinding. After the defatting step, the meal contains 8-10% water (w/w), making it unnecessary to add the amount of water needed for enzyme activity. The reactions are carried out in buffer-saturated organic solvents to avoid a possible drying effect of the solvent on the biocatalyst. Further addition of water to the reaction results in lower conversions and values,... 

It thus appears that the enantioselectivity of CALB for this reaction in the solid/ gas bioreactor is similar to that in an organic liquid medium. Solid/gas biocatalysis therefore offers important potential for production of enantiomerically pure compounds, provided that these transformations involve components having a degree of volatility. Furthermore, as the addition of solvents is avoided in this system, separation and purification during downstream processing are simplified, and side reactions are suppressed. 

The LPS silica is prepared by extracting the water from a low solids hydrogel with an organic solvent to avoid the compression of aqueous surface tension. This leaves a fragile catalyst of very high pore volume. Such preparations often provide dramatic examples of the effect of pore volume because the same gel dried directly in an oven will frequently be less active or even completely dead. Invariably, nitrogen sorption shows the inactive silica to contain a low pore volume mainly inside small pores, e.g., less than 60 A diameter. In contrast, the active sample dried by extraction usually has equal or greater volume inside small pores, and, in addition, considerable volume... 

In analogy to the relation between SPE and SPME discussed below, a refinement of LEE is achieved by the LLLME method. Analytes in a stirred matrix solution (the donor) are extracted into a thin solvent film filling the pores in the walls of a hollow fiber and diffuse into a collecting solution (the acceptor) filling the inner void of the hollow fiber. The enrichment factor depends not only on the volume ratio between the donor and the acceptor, but also on the operational conditions. The main advantages of the method are simplicity of operation, low cost, the scarce use of organic solvents and avoidance of evaporation operations120. 

An additional broad area of utilization of GC is the determination of residual solvents (organic volatile impurities). The solvents allowed for use in the synthesis and manufacture and their respective residual limits have been addressed by the ICH. Tests for residual solvents should be conducted whenever production or purification processes may result in the presence of such solvents. This mandates that residual solvents be determined in drug substances. For drug products, residual solvent levels may be calculated from the levels in the ingredients used to produce the drug product unless class 1 (to be avoided) or class 2 (to be limited) solvents are used in the manufacture of the drug substance, excipients, or drug product. ... 

Ionic liquids used as the green solvents could avoid the utilization of volatile hazardous organic solvents, simplify the product isolation in the homogeneous catalytic reaction systems, and provide the access to the recovery and reuse of the catalytic systems as well besides, it can avoid the pollution. Furthermore, the ionic liquids could act as the catalysts, ligands, or supports of reagents through the functionalization of the ionic liquids. 

Another modification of the Dess-Martin periodinane oxidation is the use of ionic liquids such as hydrophilic [bmim]BF4 and hydrophobic [bmim]BF6 to increase the rate of reaction." These solvents are more environmentally friendly than conventional organic solvents and avoid the use of high boiling polar organic solvents such as DMSO or DMF. 

Natural CNSL itself (from solvent extraction), rich in anacardic acid has been initially reacted in aqueous systems in concentrated basic solution with paraformaldehyde and after addition of composite material has been heated and cured, during which process some decarboxylation of the anacardic acid polymer occurred, as shown in the scheme, to afford a particle board product (ref. 283) having excellent mechanical properties and resistance to water penetration. The customary use of organic solvents was avoided in this process. 

In addition to such important factors as the choice of organic solvent, the avoidance of emulsions, and the actual method of extraction—batch, continuous, or counter-current—there are other important and easily controlled experimental variables. In... 

Importantly, the hydrogel is formed in an all-aqueous environment in which the use of organic solvents is avoided. Crosshnking is estabhshed by stereocomplex formation... 

To reduce the affinity of powders with respect to aqueous or organic solvents To avoid caking phenomena during storage and transport To improve appearance, taste, or odors of products To conserve nutrients contained in food products To functionalize powders (catalysts, enzyme-coated detergents, etc.)... 

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