For complexation equilibria

Rojas A, Gonzalez I (1986) Relationship of Two-dimensional predominance-zone diagrams with conditional constants for complexation equilibria. Anal Chim Acta 187 279-285... 

In a simple liquid-liquid extraction the solute is partitioned between two immiscible phases. In most cases one of the phases is aqueous, and the other phase is an organic solvent such as diethyl ether or chloroform. Because the phases are immiscible, they form two layers, with the denser phase on the bottom. The solute is initially present in one phase, but after extraction it is present in both phases. The efficiency of a liquid-liquid extraction is determined by the equilibrium constant for the solute s partitioning between the two phases. Extraction efficiency is also influenced by any secondary reactions involving the solute. Examples of secondary reactions include acid-base and complexation equilibria. 

Solubility of AgCI as a function of pCI. The dashed line shows the predicted SAgci, assuming that only reaction 8.1 and equation 8.2 affect the solubility of AgCI. The solid line is calculated using equation 8.7, and includes the effect of reactions 8.3-8.5. A ladder diagram for the AgCI complexation equilibria is superimposed on the pCI axis. 

Mechanism ofLP Oxo Rea.ction. The LP Oxo reaction proceeds through a number of rhodium complex equilibria analogous to those ia the Heck-Breslow mechanism described for the ligand-free cobalt process (see Fig. 1). 

The monohydroxypteridines have been shown to exist predominantly in the oxo forms, but complex equilibria are nevertheless present for example, pteridin-2-one (168) can exist in four tautomeric forms. Comparison of the ultraviolet spectra of methyl derivatives corresponding to these four forms (i.e., 169-172) with that of the... 

It has been shown that ab initio total energy DFT approach is a suitable tool for studies of phase equilibria at low temperatures and high pressures even when small energy differences of the order of 0.01 eV/mol are involved. The constant pressure optimization algorithm that has been developed here allows for the calculation of the equation of state for complex structures and for the study of precursor effects related to phase transitions. 

First Concept in Catalyst Design. Shifting Complexation Equilibria for Ion-Exchange by Oxidation of the Organic Chelates... 

Results of relaxation measurements on spin-state equilibria in solution are available for complexes of iron(II), iron(III), and cobalt(II). The results comprise values of relaxation time r, rate constants for the forward and reverse reactions feLH activation parameters AH and AS for the two opposed... 

Fig. 9a-c. Relative positions of LS and HS potential energy surfaces for complexes showing spin-state equilibria associated with different amounts of geometric reorganization a no intersection of potential surfaces b intersection accompanied by moderate displacement of the minima of potential surfaces c (avoided) interseetion accompanied by sizeable displacement of the minima of potential surfaces. AEq = AG° is the difference of zero-point energies of LS and HS states, E = AG h and jlj... 

Zwitterionic character is notable in several therapeutic area series, e.g. in angiotensin-converhng enzyme inhibitors, quinolone anhbacterials and thrombin inhibitors. The aqueous solubiUty measurement of zwitterions is very pH dependent as might be expected. The relationship of aqueous solubiUty to ionization state is extraordinarily complex if the zwitterion is of the type capable of an equi-Ubrium between true zwitterion and formally neutral forms (e.g. as in a quinolone antibacterial). For these types of complex equilibria, salt effects on solubility may be unexpectedly large, e.g. solubility unexpectedly may track with the chaotropic character of the salt... 

According to R. Brdicka and K. Vesely the carbonyl form of formaldehyde is reduced and the limiting kinetic current is given by the rate of the chemical volume reaction of dehydration. An analogous situation occurs for the equilibria among complexes, metal ions and complexing agents if the rates of complex formation and decomposition are insufficient to preserve the equilibrium. A simple example is the deposition of cadmium at a mercury electrode from its complex with nitrilotriacetic COO"... 

Lemire and Garisto [60] concluded that the only important complex formed in a nearly neutral solution in Tc(OH) (C03)2. Erikson et al. [61] determined the logarithm of the equilibrium constants for the equilibria involving Tc02 nH20 species as shown in Table 3. 

Leggett, D. J., Ed. (1985). Computational Methods for the Determination of Formation Constants. Plenum Press, New York. A high-level presentation of the theory of complex equilibria and computer programs for mathematical analysis. 

Rings with rigid pendant arms . The interesting ligand tris(2,3-dihy-droxybenzoyl)l,5,9-triazacyclotridecane (102), was synthesized specifically to act as a reagent for Fe(in) (Weitl Raymond, 1979). It is structurally quite closely related to enterobactin (103), the natural molecule used by E. coli to transport Fe(m) through its cell walls. The protonation and complexation equilibria of Fe(m) with (102) have been... 

Another factor that can possibly affect the redox potential in biological systems is the presence of secondary chelating agents that can participate in coupled equilibria (3). When other chelators are present, coupled equilibria involving iron-siderophore redox occur and a secondary ligand will cause the siderophore complex effective redox potential to shift. The decrease in stability of the iron-siderophore complex upon reduction results in a more facile release of the iron. Upon release, the iron(II) is available for complexation by the secondary ligand, which results in a corresponding shift in the redox equilibrium toward production of iron(II). In cases where iron(II) is stabilized by the secondary chelators, there is a shift in the redox potential to more positive values, as shown in Eqs. (42)—(45). 

Measurements of binding curves without influencing the equilibria can be performed if the readout for complex formation is correlated with a change in a macroscopic signal. This can be either a change in fluorescence intensity, fluorescence polarization, optical absorption, or heat of association (see next chapter). Assume an equilibrium... 

Phase behavior 1n concentrated aqueous electrolyte systems is of interest for a variety of applications such as separation processes for complex salts, hydrometal 1urgical extraction of metals, interpretation of geological data and development of high energy density batteries. Our interest in developing simple thermodynamic correlations for concentrated salt systems was motivated by the need to interpret the complex solid-liquid equilibria which occur in the extraction of sodium nitrate from complex salt mixtures which occur in Northern Chile (Chilean saltpeter). However, we believe the thermodynamic approach can also be applied to other areas of technological interest. 

The correlation has also been applied to a wide variety of ternary and quarternary systems by Vega and Funk (1 9). Again, the correlation is very good for the concentrated region and was effective in describing complex equilibria occuring in the quaternary system of NaCI-NaNOg-NapSO.-hLO. 

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