Log k value

Fig. 2. Observed vs. calculated rates of hydrolysis of enamines at 24.8°. Drawn lines calculated log k values. Observed values o for 4-(2-methylpropenyl)morpholine A for l-(2-methylpropenyl)piperidine for l-(2-methylpropenyl)pyrrolidine. Values are corrected for buffer contributions (23).

In spite of the complicated nature of disproportionation equilibria, we think that the J m values alone can give useful information on log K values through eqs. (120) and (128), because it appears that the enthalpy change, AH, accompanying disproportionation can be treated within many reaction series as... 

For each compound the log k values were obtained by isocratic methods at three different methanol water ratios and the logkw value was derived by extrapolation to 100% water. 

Fig. 7. Plot of log K values for Bi3+ complexes with unidentate ligands vs log Kt values for corresponding complexes with CH3Hg+. Data at 25°C and corrected to ionic strength zero, from Ref. (22).

Abraham, M. H., P. L. Grellier, D. V. Prior, P. P. Duce, J. J. Morris, and P. J. Taylor. 1989a. A Scale of Solute Hydrogen-bond Acidity Based on log K Values for Complexation in Tetrachloromethane. J. Chem. Soc., Perkins Trans. 2, 699. 

An electrophoretic method was described by Srivastava et al. [40] to study equilibria of the cited mixed ligand complex systems in solution. Stability constants of the Zn(II) and Cd(II) complexes were 5.36 and 5.18 (log K values), respectively, at an ionic strength of 0.1 and a temperature of 35 °C. 

An ionophoretic method was described by Tewari [41] for the study of equilibria in a mixed ligand complex system in solution. This method is based on the movement of a spot of metal ion in an electric field with the complexants added in the background electrolyte at pH 8.5. The concentration of the primary ligand (nitrilo-triacetate) was kept constant, while that of the secondary ligand (penicillamine) was varied. The stability constants of the metal nitrilotriacetate-penicillamine complexes have been found to be 6.26 0.09 and 6.68 0.13 (log K values) for the Al(III) and Th(IV) complexes, respectively, at 35 °C and an ionic strength of 0.1 M. 

The data of Loukidou et al. (2004) for the equilibrium biosorption of chromium (VI) by Aeromonas caviae particles were well described by the Langmuir and Freundlich isotherms. Sorption rates estimated from pseudo second-order kinetics were in satisfactory agreement with experimental data. The results of XAFS study on the sorption of Cd by B. subtilis were generally in accord with existing surface complexation models (Boyanov et al. 2003). Intrinsic metal sorption constants were obtained by correcting the apparent sorption constants by the Boltzmann factor. A 1 2 metal-ligand stoichiometry provides the best fit to the experimental data with log K values of 6.0 0.2 for Sr(II) and 6.2 0.2 for Ba(II). 

Table 4.1. Log K values for Na+ and K+ complexes of ligandsof type (183 n = 2) in methanol3...

Two general procedures have been used to obtain AH values. The first involves the measurement of log K values over a range of temperatures the observed variation may be used to derive the required AH value. However, because of the usual errors inherent in log K determinations coupled with the limited temperature range normally possible, AH values obtained in this manner tend to be somewhat unreliable. In contrast, the direct determination of AH using calorimetry commonly results in values which are considerably more accurate. Nevertheless, such calorimetric determinations may still not be easy for particular macrocyclic systems. Difficulties can arise in measuring the total heat evolved for metal complexation when long equilibration times are necessary. To lessen such problems, sensitive calorimeters have been used which are able to integrate the heat released over an extended time. 

In 1M NaC104 uncertainties are relatively large as 7C, values are so small log K values for glycolate are almost identical (see also Ref. (239)). 

To explore the differences between the methods, we use spece8 to calculate at 25 °C the solubility of gypsum (CaSCU 2H2O) as a function of NaCl concentration. We use two datasets thermo.dat, which invokes the B-dot equation, and thermo hmw. dat, based on the hmw model. The log K values for the gypsum dis-... 

The rate law is based on a surface complexation model Liger et al. (1999) developed for the hematite nanoparticles (see Chapter 10, Surface Complexation ). The >FeOH surface sites react by protonation and deprotonation to form >FeOII2h and >FeO-, by complexation with ferrous iron to form >FeOFe+ and >FeOFeOH, and to make a complex >Fe0U020H with uranyl. Table 28.1 shows the reactions and corresponding log K values. The nanoparticles are taken to have a specific surface area of 109 m2 g-1, and a site density of 0.06 per Fe2C>3. 

Hiemstra et al. (1989) have elaborated on a multisite proton adsorption model taking into account the various types of surface groups intrinsic log K values for the protonation of various types of surface groups can be estimated with this model. 

Fio. 1 Relation between log K and the ratio of cation diameter to cavity size for (cfa-syn-c r)-dicyclohexyl-18-crown-6 [20] in water at 2S°C. Ionic diameters taken from Pedersen (1967a), and log K values from Izatt et al. (1976a) and Frensforf (197 la)... 

Several investigators have studied the effect of substituting N or S for O on the cation affinity of crown ethers. Log K values for 15-crown-5 [2] and... 

The introduction of four 2,2-dimethyl- 1,3-dioxolanyl groups into 18-crown-6 to form compound [245] causes the log K value to drop from 6.48 to below 1.7 (Laidler and Stoddart, 1976). Replacement of two CH2OCH2 units... 

Effect of remote and intra-annular substituents on log K values for t-BuNHjX complexes of 1,3-xylyl-crown ethers 1256] in CDC13 at 24°C ... 

Izatt et al. (1978c) have determined the values of log K, AH, and TAS for diazonium complexes of 18-crown-6 in methanol at 25°C. These values were 2.26, —10.03 kcal mol-, and —6.95 kcal mol-1 for 4-methylbenzene-diazonium, and 2.37, —14.0 kcal mol-1, and —10.8 kcal mol-1 for benzenediazonium. Strongly electron-donating groups such as Et2N depressed complexation to such an extent that log K values could not be determined. The low stability of the benzenediazonium as compared with the anilinium complex of 18-crown-6 (log K, 3.80 AH, —9.54 kcal mol- TAS, —4.36 kcal mol-1) is... 

Here is the appropriate Matlab program Ma in FSW EFA. m. The data, generated by Data eqAH4a. m, are mimicking a spectrophotometric titration of a tetra-protic acid AH4. with log(K) values of 8, 7, 6 and 2. 

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