Constant stepwise

The equilibrium constant for the formation of a metal complex is known as its stability constant. (Some authors, however, present the datum as its reciprocal, the instability constant of the complex, by analogy with the dissociation of a weak acid.) There are two kinds of stability constants stepwise (Ad, Ad, Ad,..., Kn) and overall (/ ). We will assume that there are six aqua ligands to be replaced by some other unidentate ligand Xx, in an aqueous solution of Mm+ ... 

The larger the value of the constant is, the more stable the complex (Table 12.11). The metal-ammine formation constants Ksl and Kst are known as stepwise formation constants. Stepwise formation constants1 could be used to estimate overall formation constants. For example,... 

For complexes that contain more than one ligand or central metal ion, there are two ways of writing stability constants. Stepwise formation constants are equilibrium constants for the reactions in which the central metal ion consecutively adds one ligand. An overall formation constant is the equilibrium constant for the reaction in which the central metal ion combines with all of the ligands necessary to form a specific complex. We can illustrate these two types of constants using the formation constants of the chloromercury(II) complexes as an example. For stepwise formation we have... 

The following entry defines the commonly used stability constants (stepwise, overall, conditional, association, dissociation, and pK) and relates the values to a rigorous thermodynamic definition of equilibrium constants. In addition, the article briefly outlines experimental techniques (potentiometric titration, spectroscopic methods involving ultraviolet/visible, infrared, Raman, fluorescence. and nuclear magnetic resonance spectroscopy), together with the numerical methods and computer programs that can be used to derive stability constants from such experimental data. 

Kr. In the B-emitting states, a slower stepwise relaxation was observed. Figure C3.5.5 shows the possible modes of relaxation for B-emitting XeF and some experimentally detennined time constants. Although a diatomic in an atomic lattice seems to be a simple system, these vibronic relaxation experiments are rather complicated to interiDret, because of multiple electronic states which are involved due to energy transfer between B and C sites. 

If the stepwise stability or formation constants of the reactions are desired, for the first step log = log fej = 2.37. For the second and succeeding steps the equilibria and corresponding constants are as follows ... 

Stepwise and cumulative formation constants for selected metal-ligand complexes are given in Appendix 3C. 

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... 

Application of NMR spectroscopy to heterocyclic chemistry has developed very rapidly during the past 15 years, and the technique is now used almost as routinely as H NMR spectroscopy. There are four main areas of application of interest to the heterocyclic chemist (i) elucidation of structure, where the method can be particularly valuable for complex natural products such as alkaloids and carbohydrate antibiotics (ii) stereochemical studies, especially conformational analysis of saturated heterocyclic systems (iii) the correlation of various theoretical aspects of structure and electronic distribution with chemical shifts, coupling constants and other NMR derived parameters and (iv) the unravelling of biosynthetic pathways to natural products, where, in contrast to related studies with " C-labelled precursors, stepwise degradation of the secondary metabolite is usually unnecessary. 

A significant achievement of Anatoly K. Babko was in the area of systematic physicochemical research of complex compounds in solution based on their photometric properties. Anatoly K. Babko showed the stability constants of complexes to be highly important, and demonstrated the relevance of the stepwise character of the dissociation of complex compounds. 

The rate constants and ko were equal to 3 x 10 and lO s respectively [Shian et al. 1980 Bratan and Strohbusch 1980]. There are two equivalent ways of stepwise transfer, and, therefore, the transition state and MEP are two-fold, if the stepwise transfer is energetically preferable. On the other hand, there is only one way of concerted transfer, which lies between the saddle points. Based on this reasoning, de la Vega et al. [1982] have found that the barrier for stepwise transfer (25kcal/mol) is 3.1 kcal/mol lower than that for concerted transfer. These authors have proposed a model two-dimensional PES,... 

In a small integral reactor at each step of the stepwise increasing temperature, one point on a conversion versus temperature curve is received. These are all at the same feed rate and feed composition, constant pressure, and each is at a different but practically constant temperature along the tube length within every step. Since the reactor is small the attainment of steady-state can be achieved in a short time. The steadiness of conditions can be asserted by a few repeated analyses. 

This procedure can now be repeated with a base D that is slightly weaker than C, using C as the reference. In this stepwise manner, a series of p determinations can be made over the acidity range from dilute aqueous solution to highly concentrated mineral acids. Table 8-18 gives pS bh+ values determined in this way for nitroaniline bases in sulfuric and perchloric acid solutions. This technique of determining weak base acidity constants is called the overlap method, and the series of p kBH+ values is said to be anchored to the first member of the series, which means that all of the members of the series possess the same standard state, namely, the hypothetical ideal 1 M solution in water. 

In contrast to the stepwise oxidation of sodium hyponitrite in liquid N2O4, the oxidation goes rapidly to the nitrate ion in an inert solvent of high dielectric constant such as nitromethane ... 

By convention the displaced water is ignored since its concentration is essentially constant. The overall stability (or formation) constant can clearly be expressed in terms of the stepwise constants ... 

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