Association constant = /< value

Table 2 lists limiting equivalent conductance and association constant values for a number of 1 1 electrolytes in the solvents of Table 1, and Table 3 gives single ion mobility values. The data include results that appear to have sufficient precision to give meaningful values when treated by the Fuoss-On-sager conductance equation. In a few cases data of somewhat lower precision have been included to indicate the magnitude of the association constants, which can often be determined with fair accuracy from such data. 

Mono and bis complexes of Pr3+ and Nd3+ in aqueous solutions of iminodiaceticmono-methylenephosphonic acid have been studied over the pH range 1-12 by visible spectroscopy and association constant values determined.365... 

Table 8 Log Association Constant Values for Lanthanide-Crown Ether Complexes in Propylene Carbonate1164...

These complexes, unlike the crown ether complexes but similar to the aza-crown and phthalocyanine complexes, are fairly stable in water. Their dissociation kinetics have been studied and not surprisingly they showed marked acid catalysis.504 Association constant values for lanthanide cryptates have been determined.505,506 A study in dimethyl sulfoxide solution by visible spectroscopy using murexide as a lanthanide indicator showed that there was little lanthanide specificity (but surprisingly the K values for Yb are higher than those of the other lanthanides). The values are set out in Table 9.507... 

Association constant values for the 1 1 porphyrin-anion complex on the nanoparticle surface. ... 

This equation accounts for experimental association constant values higher than theoretical ones because KA > Ki. Moreover, we may deduce that when cations are equal, KA is smaller for smaller anions, which means that they have a greater charge density and thus are more basic, since K2 is lower for them. On the contrary, KA values decreasing with an increase in the size of the anion have been observed in aprotic solvents like TMS (II), acetone (41), nitrobenzene (42), nitromethane (43), acetonitrile (44), and 1,1,3,3-tetramethylurea (45). This order can be understood if one considers that in this class of solvents the anions are scarcely solvated so that association is affected mainly by the strength of cation-anion interaction, which, with the cations being equal, increases with an increase in the anion charge density. 

The Ze/-amine cations (IV-VI) and the tartrate anion were suggested to be better disposed stereochemically [307]. The association constants for these complexes are of the same order of magnitude (Z-tartrate dianion) or ever higher (d-tartrate dianion) than with the [Sb2(d-tart)2] - anion. Such changes in the association constant values for systems with two chiral anions may be caused by different factors... 

When the experimental data are sparse, or the experiments were not well designed, the estimated uncertainties in some association constant values are large. If we omitted these association constants, and only generated interaction coefficients, the propagated uncertainties would not be reduced. They would simply reappear in a different guise. 

By means of this equation, measured association constant values can be converted directly into a key thermodynamic parameter. Otherbinding thermodynamic parameters maybe obtained through thermodynamic equations or preferentially measured by ITC. The key parameters are standard enthalpy change of binding and standard entropy change of binding... 

Fluorescence lifetime data of 1, 4, 5, and 6 in presence of 10 M -CD were collected with frequency-domain fluorometry. These probes gave only 1 1 complexes with P-CD [58] and, given the association constant values, the complex molar fraction was >0.95 for 4 and 5 and 0.1 for 6. The fluorescence decay of all the probes was best described by unimodal Lorentzian lifetime distribution [51,59] rather than by a mono- or biexponential function corresponding to the emission of the complexed and the free probe. This distribution was attributed to the coexistence of molecules included in the cavity to different extents. It was proposed that, in the case of 4, the apolar benzene ring enters the cavity first and penetrates until the whole naphthalene is included. This is the most stable and, hence, the most populated conformation of the complex. The distribution of the lifetimes suggests that at any time there is an ensemble of molecules in different stages of complexation which have slightly different lifetimes. 

The mechanism of facilitated ion transfer reactions is not unique, as it depends on the different concentrations of both the cation and the ligand in the two phases, and also on the association constant values for the complexation equilibria in the water and organic phases. Different limiting situations can be obtained for the different systems discussed here, but any intermediate situation can only be resolved by solving the set of differential equations for mass transport of the different species involved. Furthermore, the liquid-liquid interface, not being a sharp physical boundary, makes it difficult to differentiate cases where the ionophore is distributed between the two phases. 

Equation (6.3) relates to the temperature range of 50-600 °C and gives similar association constant values as Eq. (6.1), except at 50 C where the constant derived from Eq. (6.1) is less positive at the saturation pressure of water. Nevertheless, all the data of Ho, Palmer and Wood (2000) are retained in the present study at the temperatures reported in their work up to 350 C. 

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