Stability constants definition

Molecular Switches, p. 917 Molecular-Level Machines, p. 931 Nuclear Magnetic Resonance Spectroscopy, p. 981 Rotaxanes and Pseudorotaxanes, p. il94 Self-Assembly Definition and Kinetic and Thermodynamic Considerations, p. 1248 Stability Constants Definition and Determination, p. 1260 The Template Effect, p. 1493 X-Ray Crystallography, p. 1586... 

Stability Constants Definition and Determination, p. 1360 Viruses as Host Assemblies, p. 1563... 

Pyrrole- and Polypyrrole-Based Anion Receptors, p. 1176 Selectivity Thermodynamic and Kinetic, p. 1225 Stability Constants Definition and Determination, p. 1360 Strong Hydrogen Bonds, p. 1379... 

Although there is no controversy about the basic definition of stability constants, physical chemists and biochemists handle the concepts involved and the resulting calculations differently. Physical chemists think in terms of reactive species and biochemists in terms of total concentrations of components, A further source of confusion is the differing definitions of apparent constant. To a physical chemist the stability constant for MgATP formation... 

Few workers [288, 290] have determined the stability constants of rare earth-nitrate complexes. The stability constants for the MX2+ species of several rare earths are compared in Table 19. It will be noticed from the table that the k values for the species MX2+ show a definite increase in the light rare earth region reaching the highest value at europium and then slowly decreasing. 

Since some reactants are usually ionic, one must decide on some mixing rule. Usually the concentration of an individual medium ion or the ionic strength is kept constant. (The mixing rule is indicated by 3M Na(ClQ ), 3M (Na)C104 in the Tables of Stability Constants (18).) Whichever rule one uses, this will not change the definitions below. 

This method is worth investigating further. An analysis of the stability of the formulae resulting from the method is yet to be done. There are some features to note. Considering the constants definitions above (9.36), there is an apparent problem if A = 1/12. In fact, if the whole (9.35) is multiplied by 1 — 12A, then this problem becomes a possible advantage, as that equation then simplifies, for A = 1/12, to... 

From the definition of the stability constants, we know that [HgCr] = 7ri[Hg2+][Cr] and [HgClJ = etc. Thus,... 

Stability constant comparisons should be made with some caution, since the accuracies of some values may be no better than 1, and experimental conditions (ionic strengths and the salts used to maintain them) are not identical for all systems. Nonetheless, the Table 3 values give some idea of relative stabilities for a range of ligands. The order of logmA i values for the halide ions should be noted, for comparison of this set of values for Zn + with analogous values for Cd + and Hg + (Table 4) positions these cations according to the Hard Soft Acids and Bases principle, with Zn + just on the hard side, Cd + just on the soft side, of the hard/soft border, and Hg + definitely soft. 

It is obvious that not all residues that are folded are protected from exchange, since they can be exposed to the solvent in the native state or become exposed because ad]acent or complementary surfaces become unfolded. The statistical definition of the protection factors has the same form as that of the stability constants (equation 1) and can be expressed in terms of the folding probabilities... 

The values of stability constants of surface complexes and other parameters used in modeling of specific adsorption were reported in preceding section of this chapter and in Tables 4.1 and 4.2, but these stability constants were not yet defined. Explicit definition of the stability constant for each surface species separately would be rather space consuming, considering the number of surface species used in different publications to model specific adsorption, as reported in Chapter 4. Fortunately, there are generally accepted standards by formulation of the stability constants of... 

This leads to unique definition of the stability constants of monodentate surface complexes involved in the specific adsorption of cations. Thus, reaction (5.65) rather than reactions (5.66)-(5.68) should be chosen as a standard definition, according to the above standards. The exact definition of the stability constant of the =TiOCd species in the present example depends on the electrostatic position of Cd in the surface complex. It should be also emphasized that even with fixed electrostatic position of Cd, the numerical value of the equilibrium constant of reaction (5.65) depends on the choice of the model of primary surface charging. The details on the models of primary surface charging are not given in the tables in Chapter 4, and the reader is referred to the original publications. 

Applications of the 1-pK or MUSIC models to surface complexation are rather rare, but a few examples can be found in Tables 4.1 and 4,2. These models require somewhat different standard definition of the stability constants of the surface species than outlined above for the 2-pK and TLM model, because neutral =SOH groups do not occur 1-pK model. Deprotonated surface species, e.g. AIOH " (cf. reaction(5.23)) are usually set as the components in the definition of the surface complexes responsible for the specific adsorption in the framework of the 1-pK and MUSIC models. There is some discord between such definition and the above definition in the framework of the 2-pK model. For example the =SiOH species is used as the component in the 2-pK and TLM models, and the =SiO species is suggested by the definition proposed for the I-pK and MUSIC models. 

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