Apparent formation constants

Lopez-Nicolas JM, Nunez-Delicado E, Perez-Lopez AJ, Carbonell A and Cuadra-Crespo P. 2006. Determination of stoichiometric coefficients and apparent formation constants for (3-cyclodextrin complexes of trans-resveratrol using reversed-phase liquid chromatography. J Chromatogr A 1135 158—165. 

C. Moeder, T. O Brien, R. Thompson, and G. Bicker, Determination of stochio-metric coefficient and apparent formation constant for a- and P-CD complexes of teipenes using reversed phase liquid chromatography, J. Chromatogr. 736 (1996), 1. 

This analysis leads to a value of 9.07 0.70 X 10 /sec for the benzimidazole dissociation-rate constant at 5°C, a value substantially higher than that calculated by Milton and T.L. Brown [109] at 25°C. Furthermore, the data permit a calculation of the apparent formation constant of base-on methylcobalamin from the base-off, but unprotonated species. This equilibrium constant has the startling value of 0.43,... 

Cheng [25] applied Job s method to the determination of the apparent formation constant of the Hf-xylenol orange (XO) complex using the method of mixtures of equimolar solutions. This is a rapid, though probably not too accurate, method of estimating the formation constant of a colored complex with the mole ratio 1 to 1. Application of this method gave a value of A = 1.6 x 10 for the Hf-XO complex formational constant in 0.8 N HCIO4. The formation constants of the cerium, titanium, cadmium, and UO2 [26] complexes have also been reported. 

The antitumour agent Cu(kts) (kts = 3-ethoxy-2-oxobutyraldehyde dithio-semicarbazonate) has an extremely large apparent formation constant at pH... 

The thermodynamic parameters (AH, AS, and AG) values obtained for the formation of inclusion complex (Table 40.6) were determined from temperature dependence of apparent formation constants, by using classical van t Hoff equation and plotting In K versus l/T (Tong, 2001) ... 

Reaction of chromium(ii) with pyridine-2,4-dicarboxylic acid yields two radical complexes of Cr, one of which is active in reducing cobalt(iii) complexes, the other not. The inactive form is formed in reversible equilibrium, and is believed to be the chelate (30), with apparent formation constant A app = /sT/[H+]x 50 at 20 °C in I.2M-HCIO4. The active form, possibly (31), is not detected as such, but is an intermediate postulated in the reaction [Co(NH3)spy] + + Cr +, when accelerated by the presence of the organic acid. ... 

The inclusion complex formation between frans-resvera-trol and P-CD was investigated using a Cjg column as stationary phase and methanol-water mixtures as mobile phases. The apparent formation constants were calculated under different chromatographic conditions. The... 

Table I. Apparent formation constants (A sb) for Schiff-bases derived from PLP and alkylammonium species at 30.0 C. ...

However, these four coupled equilibria from Scheme 12.1 are not the full story. Boronic acids readily form stable complexes with buffer conjugate bases (phosphate, citrate and imidazole) [20], In fact, both binary boronate-X complexes are formed with Lewis bases (X), as well as ternary boronate-X-saccharide complexes. In some cases, these previously unrecognized species persist into acidic solution and tmder some stoichiometric conditions they can be the dominant components of the solution. These complexes suppress the boronate and boronic acid concentrations, leading to a decrease in the measured apparent formation constants (f pp). As a consequence, the scope of the simple diol-boronate recognition system is greatly expanded over the simple picture of Scheme 12.1. 

The reported values of log mix are 1.6 0.1 for both Tb and Lu. Since the apparent formation constants of the tris(triflate) complexes are 2.6 and 2.3, respectively (cf table 2), the affinity of the perchlorate ion for the bis(triflate) complexes is about ten times lower than the one of the triflate itself... 

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