Formation constant, stepwise

We can also construct ladder diagrams using cumulative formation constants in place of stepwise formation constants. The first three stepwise formation constants for the reaction of + with NH3... 

Stepwise formation constants have been determined in the system Hg2+/Cl-/diethylenetriamine (dien) and related systems by potentiometry. Thermodynamic parameters have been calculated and the contribution of the entropy term to complex stability discussed.208... 

The thermodynamic stability of metal ions are denoted by stepwise formation constants as shown in equations 1.1-1.3 (charges omitted for simplicity). ... 

The thermodynamic stability of a complex ML formed from an acceptor metal ion M and ligand groups L may be approached in two different but related ways. (The difference between the two approaches lies in the way in which the formation reaction is presented.) Consistent with preceding sections, an equilibrium constant may be written for the formation reaction. This is the formation constant Kv In a simple approach, the effects of the solvent and ionic charges may be ignored. A stepwise representation of the reaction enables a series of stepwise formation constants to be written (Table 3.5). 

In Chapter 3 we described how an uncharged metal complex MA is formed from a metal ion central atom) through a stepwise reaction with the anion A (ligand) of a monobasic organic acid, HA, defining a stepwise formation constant k , and an overall formation constant (3 , where... 

The average ligand number can be used to obtain approximate equilibrium constants, as described by [65], assuming that at half integer -values the two adjacent complexes dominate e.g., at = 0.5 the species and MA dominate, while at il = 1.5 MA and MA dominate, etc.. The following expression for the stepwise formation constant is approximately valid at... 

Ki stepwise formation constant for ith complex (e.g., MLj) overall extraction constant... 

PVP were calculated by computer, using the modified method of Bjenum, and the constants obtained are plotted in Fig. 9 together with those of a pyridine-Cu systemS5 In the monomeric pyridine system, the stepwise formation constant decreases with the number of coordinated ligands because the number of vacant sites on the Cu ion, or the ligand-accepting ability of the Cu ion, decreases with succes-... 

Fig. 9. Stepwise formation constants of poly(4-vinylpyridine)-Cu complexes55) degree of polymerization of PVP ...

Gregor et al66 reported the Cu-complex formation of poly(methacrylic acid) (PMA) resins crosslinked with 1% or 9% divinylbenzene. The formation constants of the Cu complexes with the resins were smaller than that of noncrosslinked PMA. The stepwise formation constants decreased from Ki to KA in the resin system, which was the opposite of the noncrosslinked PMA system. The rigidity of the polymer-ligand chain was considered to hinder chelate formation. Formation constants of the PMA resin were also reported by Gustafson era/.67. The formation constant of the noncrosslinked PMA decreased for various metal ions ... 

Formation constants are the equilibrium constants for complex ion formation. The stepwise formation constants, designated K, are defined as follows ... 

Br0nsted-Lowry acid enthalpy change neutralization stepwise formation constant... 

Overall (p) and stepwise (K) formation constants were distinguished in Box 6-2. The relation between pn and the stepwise formation constants is... 

A macromolecule may often be able to bind several molecules of a second compound X. Consider the case in which the macromolecule P binds successively one molecule of X, then a second, and a third, up to a total of n. We define the stepwise formation constants, Kv K2,..., f(n, as follows ... 

Remember that these are reversible reactions even though unidirectional arrows are used. The general expression for the zth stepwise formation constant is given by Eq. 7-7. 

A similar equation can be written for the general case. Note that the concentration of P does not appear in Eq. 7-10 and that Y is a function only of [X] and the stepwise formation constants. Such equations define the isotherms for binding of two or more molecules of X to P. From an experimental plot of Y (or of AA) vs [X] or log [X], it is possible in favorable cases to determine the stepwise constants Kp K2,Kn. However, this becomes quite complicated. To simplify Eq. 7-10 and the corresponding equation for the general case, we can group the constants together and designate the products of constants (Kp K]K2, etc.) as V q, y2,. 

The stepwise formation constants for the displacement of H20 from [Cd(H20)6]2+ by imidazole have been measured.419 On the basis of enthalpy changes, a change in coordination from octahedral to tetrahedral and then back again is postulated at certain steps (Scheme 2). 

The stepwise formation constant for formation of HgCI3 is not known in solvent 96% methanol —4 % water, but is likely to be quite small, perhaps of the order of 10 l.mole-1. At the kinetic concentration used (tHgCl2l = 0.01 M), such a formation constant would result in not more than 10 % of the original mercuric chloride present being converted into HgCl3. ... 

The constants kn are stepwise formation constants, while the K are overall formation constants. They are simply related by ... 

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