Complexes hydrophilic

Simple organic molecules such as small carboxylic acids (oxalate, acetate, malonate, citrate, etc.), amino acids and phenols are all ligands for metals. Such compounds may all occur as degradation products of organic matter in natural waters. The complexes formed are typically charged hydrophilic complexes. The stability of the metal complexes with these ligands is, however, moderate in most cases. Model calculations including such compounds at realistic concentrations indicate that their effects on speciation are relatively small [29],... 

In the following section, the role of the various types of complexes mentioned above will be discussed with regard to various mechanisms of interactions at biological interphases. It is clear that metal ions and hydrophilic complexes cannot distribute into the membrane lipid bilayer or cross it. The role of hydrophilic ligands has thus to be discussed in relation to binding of metals by biological ligands. In contrast, hydrophobic complexes may partition into the lipid bilayer of membranes (see below, Section 6). 

Extractions of aqueous solutions of racemic amino-acid ester salts with solutions of / -6/s(dinaphthyl)-22-crown-6 [284] in chloroform revealed the dependence of the enantiomeric distribution constant on the structure of the amino acid ester (Table 64). In order to limit the concentrations of complex in the aqueous phase, inorganic salts were added. In the case of tyrosine, serine and alanine no extraction of salt was observed obviously these salts form very hydrophilic complexes. The highest degree of chiral recognition was found with [284] and p-hydroxyphenylglycine methyl ester hexafluorophosphate [A(AG°)... 

Type IV Hydrophilic complex formation and solvent extraction... 

This example illustrates a case of considerable analytical importance, especially for the determination of complex formation constants for hydrophilic complexes, as discussed in section 4.12, when the equilibrium constants for the stepwise metal-organic complexes are of secondary interest. values are tabulated in several reference works. is a conditional constant and only valid provided no other species are formed besides the extracted one. 

STUDIES OF HYDROPHILIC COMPLEXATION BY SOLVENT EXTRACTION (TYPE IV)... 

Minor experimental modifications, such as the use of hydrophilic complex-ants to ease the scrubbing and stripping of the loaded solvents and simplify the flowsheets. 

The major drawback of phenyl derivatives of BNOPCs is that they are only scarcely soluble in classical hydrocarbon diluents without the addition of massive amounts of phase modifiers, such as TBP or TOPO. They are, however, soluble in halogenated and nitro-halogenated organic diluents (130). Furthermore, the anomalous aryl strengthening effect also increases the extraction of other fission products, such as Zr, Mo, Tc, and Fe, which can only be avoided by introducing specific hydrophilic complexants (e.g., acetohydroxamic acid). 

All partitioning processes described in today s literature that claim to separate the minor An(III) from the fission products by selective extraction of the An(III) actually perform the An(III)/Ln(III) partition from a feed arising from a front-end partitioning step, which has already separated the An(III) + Ln(III) fraction from a PUREX raffinate. There are, however, other processes that perform the An(III)/ Ln(III) partition by using a selective hydrophilic complexant, introduced either in the feed to selectively complex the An(III) and prevent their extraction, or in the stripping solution to selectively back-extract the An(III) from the loaded solvent. The development and achievements of these two families of processes ( selective extraction of An(III) and selective complexation of An(III) ) will be described hereafter. 

Under the same conditions, the TNP hydrolysis rate constants with Zn2+—cyclen 2b in the absence and presence of 10 mM Triton X-100 were 3.8 AA1 sec-1 and 9.0 X 1CT2 AT1 sec-1, respectively. The hydrophilic complex 2,... 

Wool, silk, hair Natural, hydrophilic Complex proteins Cationic... 

Though the polyether phosphine is capable of acting as a normal PTC [14], this result indicates that the hydrophilic complex transports the allyl acetate from the heptane phase into the aqueous phase and catalyzes the reduction to propene with sodium formate in the aqueous phase [4] (see Scheme 1). 

Carboxylated phosphine complex 3 is active for the cyanation, though this hydrophilic complex is inferior to 2 as a counter-PTC. As the cyanide anion is easily extractable, a phosphine complex having an ammonium group or a crown ether, which is insoluble in water [27], is also efficient for the cyanation. The catalytic efficiency is higher than that of the mixed system of lipophilic catalyst and normal... 

PTC, owing to the proximity effect caused by the conjunction of metal catalyst and normal PTC. However, the hydrophilic complexes are superior to the doubly functional catalysts in the cyanation. 

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