Equilibrium constant complex formation

Table 3. Hydrolysis, Equilibrium, and Complex Formation Constants...

The Ki value is the dissociation constant of an enzyme-inhibitor complex. If [E] and [I] are the concentrations of enzyme and its inhibitor and [El] is the concentration of the enzyme-inhibitor complex, there is an equilibrium of complex formation and detachment as follows ... 

The equilibrium constants for formation of the various complexes should be identical after the experimental values are corrected for the differences in probability for their formation. Also, the stability of the last complex as reflected by Km should be independent of the fact that some of the intermediate... 

In the case of a bidentate ligand the ratio KMLJKWL)i has units of concentration in mol 1 1. If one assumes that the equilibrium constants for formation of the monoco-ordinated complexes ML and ML L are equal,2 combination of the equilibrium constants for (26) and (27) shows that the ratio... 

Although suggested to operate by a mechanism analogous to Scheme 14, the case of the catalysis by the mononuclear complex Fe(CO)5 was proposed to be more limited.86,88 Relative to the Ru catalyst, the equilibrium constant for formation of the metallocarboxylic acid adduct, Fe(C0)4(C02H)-, was found to be several orders... 

Chromium(II) chloride, 6 528t, 531, 564t Chromium(III) chloride, 6 532 physical properties, 6 528t Chromium(IV) chloride, 6 535 Chromium(III) chloride hexahydrate, physical properties, 6 528t Chromium chromate coatings, 76 219—220 Chromium complexes, 9 399 Chromium compounds, 6 526-571 analytical methods, 6 547-548 economic aspects, 6 543-546 environmental concerns, 6 550—551 health and safety factors, 6 548-550 hydrolysis, equilibrium, and complex formation constants, 6 530t manufacture, 6 538-543... 

The equilibrium constant for formation of activated complex (K ) is given by... 

Equilibrium constants for formation of complexes [Fe(CN)5L] can be derived from kinetics and independently from spectroscopic determinations. Values are given in many of the papers cited above stability constants for several pentacyanoferrate(II) complexes have been compared with those for their pentacyanoruthenate(II) analogues. " ... 

Table 10 Kinetic parameters and equilibrium constants for formation and dissociation of ternary nitric oxide complexes (in water, at 298 K). 

Equilibrium constants for formation of iron(III) complexes of several oxoanions, of phosphorus, arsenic, sulfur, and selenium, have been reported. The kinetics and mechanism of complex formation in the iron(III)-phosphate system in the presence of a large excess of iron(III) involve the formation of a tetranuclear complex, proposed to be [Fc4(P04)(0H)2(H20)i6]. The high stability of iron(III)-phosphate complexes has prompted suggestions that iron-containing mixed hydroxide or hydroxy-carbonate formulations be tested for treatment of hyperphosphatemia. " ... 

Kinetic study of the reaction of cyclopentyl-MgBr + 4-methylmercaptoacetophenone by using stopped-flow UV and IR spectroscopies also showed that the rate constant was in the range of 2-6 s in diethyl ether at 25 °C, and the rate was first order in RMgX at low concentration (ca 0.1 M) and 0th order at high concentrations (0.3-0.8 M). The results were interpreted by the mechanism which involved pre-equilibrium of complex formation and conversion of the complex to the product. 

The kinetic effects of C02 in the base catalyzed hydrolysis of some carboxylato amine cobalt(III) complexes have been reported (80-82). In the base catalyzed hydrolysis of oxalatopentaammine-cobalt(III) (80), C02 retarded the reaction due to the formation of a virtually unreactive ion-pair, f (N H .) r, 2 2 COi ]. The equilibrium constant for formation of carbonate ion-pairs with (glycinato-O) (tetraethylene-pentamine)cobalt(III), (81) and (o-methoxybenzoato) (tetraethylenepentamine)cobalt(III) (82) were, however, much smaller than for the oxalatopentamminecobat(III) and a very weak rate retardation and virtually no effect was observed in the base catalyzed hydrolysis of the latter two complexes. 

Table 19 Equilibrium Constants for Formation of Mono-fi-diketone Complexes of V02+ in Aqueous Solution at 25 °C...

Problems in this chapter include some brainbusters designed to bring together your knowledge of electrochemistry, chemical equilibrium, solubility, complex formation, and acid-base chemistry. They require you to find the equilibrium constant for a reaction that occurs in only one half-cell. The reaction of interest is not the net cell reaction and is not a redox reaction. Here is a good approach ... 

EDTA (ethylenediaminetetraacetic acid) (H02CCH2)2NCH2CH2N-(CH2C02H)2, the most widely used reagent for complexometric titrations. It forms 1 1 complexes with virtually all cations with a charge of 2 or more, effective formation constant Equilibrium constant for formation of a complex under a particular stated set of conditions, such as pH, ionic strength, and concentration of auxiliary complexing species. Also called conditional formation constant. 

The title olefins form complexes with Ni(0) with equilibrium constants for formation decreasing in the order ethylene > styrene > propylene 1-hexene > disubstituted alkenes (28). With ethylene and styrene the (olefin)NiL2 complexes have been isolated with L = P(0-o-tolyl)3. Addition of HCN to solutions of the pure olefin complexes results in rapid and complete conversion to alkylnickel cyanide intermediates which are spectroscopically detectable subsequent C—C coupling gives the observed nitrile products propionitrile from ethylene and (predominantly) 2-phenylpropion-itrile from styrene (47). The same alkyl intermediates are formed when ethylene and styrene are added to HNiL3CN [L = p(0-o-tolyl)3]. 

The formation of a complex ion is a stepwise process, and each step has its own characteristic equilibrium constant. For formation of Ag(NH3)2+, the reactions are... 

The stability of a complex ion is measured by its formation constant Kf (or stability constant), the equilibrium constant for formation of the complex ion from the hydrated metal cation. The large value of Kf for Ag(NH3)2+ means that this complex ion is quite stable, and nearly all the Ag+ ion in an aqueous ammonia solution is therefore present in the form of Ag(NH3)2+ (see Worked Example 16.12). 

The equilibrium constant for formation of the activated complex from reactants has been given (Equation (4.25)), and substitution into the rate expression, Equation (4.20), and cancellation of terms gives... 

The extent of 1 1 complex formation decreases non-linearly with increasing ionic strength because the equilibrium constant for formation (logfC) is related to ionic strength (/) (Sposito, 1989, p. 80) ... 

Complexes of cobalt (III) containing coordinated perrhenate ion have not previously been reported. % They are of special interest because of their close relationship to the unstable perchlorate complexes and are of use in studies on the mechanism of hydrolysis. Since the equilibrium constant of formation is small and [Co(NH )5(HjO)](Re04) -2H20 is relatively insoluble, the present procedure is similar to that used previously for mom common complex ions. 

Stability constant — is the - equilibrium constant of formation of a - complex. The reciprocal quantity is called instability constant. Extensive compilations of various kinds of stability constants are available [i—iv]. Stability constants are reported for a given ionic strength (or extrapolated to zero ionic strength), and pH. In many cases, stability constants can be determined with the help of electrochemical techniques, e.g., -> chronopotentiometry, -> potentiometry, -> polarogra-phy, and - voltammetry, provided that the systems exhibit -> electrochemical reversibility, and some other prerequisites are fulfilled [v]. See also -> conditional equilibrium constants. 

Rate and Equilibrium Constants for Formation of Heterocyclic Meisenheimer Complexes ... 

With a further assumption, we can define two useful kinetic regions. If k dif > kel, then kq = Kdifkel, where Kdif is the equilibrium constant for formation of the encounter complex, i.e., Kdif = kdif/k dif. In this region, kcl values can be estimated from Stem-Volmer procedures, which measure kq values. In the second region, k dif < ke and kq = Kdif. In this case, the reaction is dominated by diffusion dynamics and is said to be diffusion-controlled. 

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