Complex formation constants for

Table III. Selected complex formation constants for plutonium (at 25°C and 1=0) (41).

The complex formation between hydroperoxides and HALS derivatives proposed for the preceding reaction was recently postulated by two different groups of investigators. First, Carlsson determined a complex formation constant for +00H and a nitroxide on the basis of ESR measurements—. Secondly, Sedlar and his coworkers were able to isolate solid HALS-hydroperoxide complexes and characterize them by IR measurements. The accelerated thermal decomposition of hydroperoxides observed by us likewise points to complex formation. It is moreover known that amines accelerate the thermal decomposition of hydroperoxides-. Thus Denisov for example made use of this effect to calculate complex formation constants for tert.-butyl hydroperoxide and pyridineitZ.. 

Complex formation constants could also be determined directly from UV spectrophotometric measurements. Addition of tert.-butyl hydroperoxide to a solution of nitroxide I in heptane at RT causes a shift of the characteristic absorption band of NO at 460 nm to lower wavelengths (Fig. 9). This displacement allows calculation of a complex equilibrium constant of 5 1 1/Mol. Addition of amine II to the same solution causes reverse shift of theC NO" absorption band. From this one can estimate a complex formation constant for amine II and +00H of 12 5 1/Mol (23 2 1/Mol was obtained for tert.-butyl hydroperoxide and 2,2,6,6-tetramethylpipe-ridine in ref. 64b). Further confirmation for an interaction between hindered amines and hydroperoxides is supplied by NMR measurements. Figure 10a shows part of the +00H spectrum in toluene-dg (concentration 0.2 Mol/1) with the signal for the hydroperoxy proton at 6.7 ppm. Addition of as little as 0.002 Mol/1 of tetra-methylpiperidine to the same solution results in a displacement and marked broadening of the band (Fig. 10b). 

Correcting Surface Complex Formation Constants for Surface Charge... 

This example illustrates a case of considerable analytical importance, especially for the determination of complex formation constants for hydrophilic complexes, as discussed in section 4.12, when the equilibrium constants for the stepwise metal-organic complexes are of secondary interest. values are tabulated in several reference works. is a conditional constant and only valid provided no other species are formed besides the extracted one. 

It is also common to measure by voltammetry the thermodynamic properties of purely chemical reactions that are in some way coupled to the electron transfer step. Examples include the determination of solubility products, acid dissociation constants, and metal-ligand complex formation constants for cases in which precipitation, proton transfer, and complexation reactions affect the measured formal potential. Also in these instances, studies at variable temperature will afford the thermodynamic parameters of these coupled chemical reactions. 

The second group of ligands have complex formation constants for the elements past gadolinium which are very nearly the same. 

In Fig. 7.30 log Ln is plotted against log K for the trans-cis isomerization of the oxalato complex. Here Ln refers to catalytic rate constants and K is the complex formation constant for lanthanide propionate complexes. The linear free energy relationship holds... 

For closely related compounds, absolute configuration has been determined from NMR spectra in the presence of chiral shift reagents [55]. For compounds with greater structural differences there are many difficulties and uncertainties to overcome before concrete results can be obtained. One of the problems is the manner of variation of induced differential shift, AA5 of resonances of protons as a function of reagent-substrate molar ratio as shown for 2-phenyl-2-butanol in Fig. 10.23. It is clear from the figure that AA<5 for a-methyl resonances increase steadily, while for -methyl protons reaches a maximum, then declines and reaches plateau. For the ortho protons, a reversal in the sense of nonequivalence occurs at a molar ratio of approximately unity. Some of the implications of such a behaviour are both theoretical and practical. If the complex formation constants for enantiomers are different, then the sense of non-equivalence should be the same for all the proton resonances, and AA<5 should increase to a maximum and level off. Since this is not the case, different magnetic environments or stoichiometries of shift reagent-substrate adducts may be the factors for the observed anomalous variation of AA5. 

Complex formation constants for lanthanide nucleotide complexes are given in Table 11.12. 

These parameters, intrinsic bond stability c and ligand sensitivity x referring to some certain hapticity, can now be applied for calculating and thus predicting complex formation constants for all the metal ions, complex fragments and organometal species in Table 2.3... 

The corresponding calculated (once again, identical) complex formation constants for bidentate binding... 

Table 3.1 Complex formation constants for E (L) = -0.323 V, representing binding into metalloproteins. Data are given for essential (biocatalytic) and some other, both essential and undefined elements...

Obviously, all acid-base equilibrium constants depend on the pH scale used. It is possible to convert approximately an equilibrium constant determined in one scale to that of another scale. The problem of different definitions of equilibrium constants needs attention when applying an infinite dilution scale complex formation constant,—for example, for CuC03(aq)—in a seawater medium. 

CORRECTING SURFACE COMPLEX FORMATION CONSTANTS FOR SURFACE CHARGE... 

Correcting Surface Complex Formation Constants for Surface Charge 573 Tableau 9.2. Adsorption of Pb on o-FeaOa... 

Salicylic acid has been selected as a model substance to provide a standard method for measuring tbe complexation capacity of crospovidone. Measurement of the complex formation constant for this substance in water gave a value of 4.11. mol1 [158]. 

Figure 9. The relative dissolution rate, R/Rf)J as a function of pH. Dashed lines were calculated by using the equilibrium and surface complex formation constants for pH 2S at 10r2 atm = /SO/ / = 10 1 M and--------------= /H2P047 =...

Different complex formation constants for the various metals increase the selectivity. 

Comparison of the complex-formation constants for bofli 1 1 (57 and 58) and 1 2 (such as 59) species ° with those obtained for the respective copper(II) complexes with parent amino acids revealed that the fructosyl moiety provides for an additional chelate effect in D-fructose-a-amino acids and as a consequence, a significant increase in the complex stability. In the absence of an anchoring chelating group, such as a-carboxylate, the D-finctosamine structure is not a good copper(II) chelator, and Cu(n) expectably does not form stable complexes with the carbohydrate in A -d-Iructose-L-lysine peptides. Although it would be expected that iron(III) complexes with D-finctose-amino acids in aqueous solutions, no related thermodynamic equilibrium studies have been done so far for this important redox-active metal. 

A potentiometric titration of PHJ with AgF in a basic anhydrous HF solution showed an initial uptake of Ag+ with an end point at [Ag]/[P] = 0.5 (formation of Ag(PH3)J) followed by a further uptake of Ag+ forming AgPHJ. The complex-formation constants for the stepwise coordination were derived [63]. 

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