Equilibrium constant water exchange

Equilibrium constants for exchange process of alcohol shell of solvates to water shell were calculated ... 

Althoi h the equilibrium constant for hydration is unfavorable, the equilibrium between an aldehyde or ketone and its hydrate is established rapidly and can be detected by isotopic exchange, using water labeled with 0, for example ... 

Controlled release epoxy formulations in which tin is chemically anchored as tributyltin carboxylate to the polymer chain are discussed. NMR evidence is presented to establish that rapid exchange exists in tributyltin carboxylates. Consequently, even the interfacial reaction between tributyltin carboxylates and chloride is very fast equilibrium constants are reported for the reaction between tributyltin acrylate in hexane and sodium chloride in water. IR spectra, gas chromatographic retention time, chloride assay, and the complex intensity pattern of the molecular ion peaks in the mass spectrum show that the product of the reaction is tributyltin chloride, suggesting that it is the chemical species responsible for antifouling activity in marine environment. 

Table 4.15 gives the equilibrium constants (for extraction, amine) for this reaction with trioctylamine in various solvents. Although the ion pairs are only slightly soluble in water, they can exchange the anion L with other anions, X, in the aqueous phase. (Note that we use L to indicate any anion, while X is used for (an alternative) inorganic anion.)... 

A change in temperature, however, does force a change in the equilibrium constant. Most chemical reactions exchange heat with the surroundings. A reaction that gives offbeat is classified as exothermic, whereas a reaction that requires the input of heat is said to be endothermic. (See Table 13-2.) A simple example of an endothermic reaction is the vaporization of water ... 

Figure 20.12 Air-water exchange of an aldehyde A converting to a diol D by a hydration/dehydration reaction. Since the diol D cannot leave the water, the slope of its concentration at the air/water interface is zero. For simplicity, the scales of A and D are chosen such that the equilibrium constant of hydration, K and the Henry s law constant of the aldehyde, KAa/vl, are 1. The dashed straight line marked [A] onre>ct,ve he>Ps t0 picture the modification due to the reactivity of A.

In Fig. 20.13 flux enhancement V / is shown as a function of the reaction/diffusion parameter q for different equilibrium constants Kr. Remember that q2 is basically the ratio of reaction time kr and diffusion time k (Eq. 20-52). Thus, q 1 corresponds to case (1) mentioned at the beginning of this section flux enhancement should not occur (V / = 1). The other extreme (vp 1, that is tT /w) was discussed with the example of proton exchange reactions (Eq. 8-6). We found from Eq. 20-49 that for this case the water-side exchange velocity v/w is enhanced by the factor (1 + Ka /[H+]). By comparing Eqs. 8-6 and 12-17 we see that for the case of proton exchange ATa/[H+] plays the role of the equilibrium constant KT between the two species. Thus, flux enhancement is ... 

In Illustrative Example 20.3 it is shown how water temperature influences the air-water exchange velocity, v,Ww. An additional temperature effect of the air-water flux results from the temperature dependence of the air-water partition constant, A,Ww. If water and air temperatures are different, the question arises whether the equilibrium between the air and water phase is determined by water temperature, by air temperature, or even by a mixture of both. Explain why Ki3lv/ should be evaluated for the temperature of the water, not the air. 

As we pointed out in the previous section, thiols have a markedly greater tendency to add to carbonyl groups than do water and alcohols. The equilibrium constant for the exchange reaction 8.46 is estimated84 to be about 2.5 x 104. 

Lind J, Shen X, Merenyi G, Jonsson B (1989) Determination of the rate constant of self-exchange of theCVCV- couple in water by 180/160 isotope marking. J Am Chem Soc 111 7654-7655 Liu Y, Pimentel AS, Antoku Y, Barker JR (2002) Temperature-dependent rate and equilibrium constants for Br (aq) + Br(aq) <=> Br2- (aq). J Phys Chem A 106 11075-11082 Marcus RA (1993) Elektronentransferreaktionen in der Chemie - Theorie und Experiment (Nobel Vortrag). Angew Chem 105 1161-1172... 

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