Exchange reactions, equilibrium constants

In effect, ion exchange chromatography exploits differences in the degree of charge and affinity (measured by the reaction equilibrium constant or molar selectivity coefficient) of ions in solution for sites of opposite charge in the stationary phase to accomplish separation. 

In order to establish accurate concentrations for estimating an isotope exchange rate, one must have an accurate value for the reaction equilibrium constant. 

The equilibrium constant for this ion-exchange reaction, which is also called the selectivity coefficient, is... 

The exchange reaction TaCUlg) + Si = Ta + SiCUlg) has the equilibrium constant given by... 

Cobalt, tetraamminepyrophosphato-structures, 1, 202, 203 Cobalt, tetraammine(sarcosine)-chirality, 1,198 Cobalt, triammine-structure, 1, 8—10 Cobalt, tricarbonato-reactions, 1,22 Cobalt, tricarbonylnitroso-exchange reactions, 1, 290 Cobalt, trichloro-equilibrium constant, 1, 517 Cobalt, trichlorobis(triethylphosphine)-structure, 1, 45... 

There is a very special case for self-exchange reactions in which the left side of the equation is identical to the right side. Accordingly, there is no free energy change in the reaction, and the equilibrium constant ( fn) must be unity (Eq. 9.29). 

The complex has been separated by ion exchange and characterised by direct analysis . The complex has a distinctive absorption spectrum (Fig. 11), quite unlike that of Np(V) and Cr(III). The rate coefficient for the first-order decomposition of the complex is 2.32 x 10 sec at 25 °C in 1.0 M HCIO. Sullivan has obtained a value for the equilibrium constant of the complex, K = [Np(V) Cr(III)]/[Np(V)][Cr(III)], of 2.62 + 0.48 at 25 °C by spectrophotometric experiments. The associated thermodynamic functions are AH = —3.3 kcal. mole" and AS = —9.0 cal.deg . mole . The rates of decay and aquation of the complex, measured at 992 m/t, were investigated in detail. The same complex is formed when Np(VI) is reduced by Cr(II), and it is concluded that the latter reaction proceeds through both inner- and outer-sphere paths. It is noteworthy that the substitution-inert Rh(lII), like Cr(III), forms a complex with Np(V) °. This bright-yellow Np(V) Rh(III) dimer has been separated by ion-exchange... 

Natural systems may be quite complex. For example, the enantiomerization of phenoxyalkanoic acids containing a chiral side chain has been studied in soil using H20 (Buser and Muller 1997). It was shown that there was an equilibrium between the R- and 5-enantiomers of both 2-(4-chloro-2-methylphenoxy)propionic acid (MCPP) and 2-(2,4-dichlorophenopxy)propionic acid (DCPP) with an equilibrium constant favoring the herbicidally active / -enantiomers. The exchange reactions... 

Determine the effectiveness factor for the ion exchange resin at 85 °C, assuming that the reaction is reversible even though the authors presumed the reaction to be irreversible in reporting their data. They note that at 100 °C the equilibrium for the reaction corresponds to a conversion greater than 94%. If the equilibrium constant for the reaction is expressed as the ratio of the t-butanol concentration to the isobutylene concentration and corrected for the temperature change in going from 100 °C to 85 °C, a value of 16.6 may be considered appropriate for use. 

A few measurements are available that relate to the ion pair acidity of ethylene and some other alkenes. Ethylene is difficult to metallate directly, but vinyl bromides and iodides undergo facile transmetallation with alkyllithium reagents. Applequist and O Brien determined the equilibrium constants of transmetallation exchange reactions as a measure of relative acidity (equations 6 and 7)25. 

By arguments very similar to those used to derive Eqs. (87)-(89), one can show that the equilibrium constants for exchange reactions of ionic vapor dimer molecules... 

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