And acidity constant

Seiler, P., The simultaneous determination of partition coefficients and acidity constant of a substance, Eur. J. Med. Chem. Chim. Therapeut. 9, 665-666 (1974). 

Table 4. Major building blocks of lipid bilayers in biological membranes and their speciation and acidity constants...

Figure 2. Relationships between k -nt ( ), ki 1" (o), and acidity constant Kjnt (i) a ZrP, (2) Y zrP, (3) Ti02, (A) Fe30 , (5) Fe203, (6) silica-alumina.

The bond dissociation energy (BDE) and acidity constant (p ) of cubane (Cub—H) have been determined experimentally by Eaton and co-workers (Hare, M. Emrick, T. Eaton, P. E. Kass, S. R, J. Am. Chem. Soc., 1997, 119, 237-238). The BDE is unusually high for a tertiary C—H bond, 427 kJ/mol, about 25 kJ/mol higher than in isobutane. The C—H bond is also quite acidic, comparable to the acidity of the N—H bond in ammonia, pK = 36, indicating an unusual stability for the anion... 

Tsutsumi, K., Shizuka, H., "Proton Transfer and Acidity Constant in the Excited State of Naphthols by Dynamic Analyses," Z. Phys. Chem., 1980, 122,129. 

Xie, T.M., Dyrssen, D. (1984) Simultaneous determination of partition coefficients and acidity constants of chlorinated phenols and guaiacols by gas chromatography. Anal. Chem. Acta 160, 21-30. 

The review starts with a discussion of the mechanism of keto-enol tautomerisation and with kinetic data. Included in this section are results on stereochemical aspects of enolisation (or enolate formation) and on regioselec-tivity when two enolisation sites are in competition. The next section is devoted to thermodynamic data (keto-enol equilibrium constants and acidity constants of the two tautomeric forms) which have greatly improved in quality over the last decade. The last two sections concern two processes closely related to enolisation, namely the formation of enol ethers in alcohols and that of enamines in the presence of primary and secondary amines. Indeed, over the last fifteen years, data have shown that enol-ether formation and enamine formation are two competitive and often more favourable routes for reactions which usually occur via enol or enolate. 

Since this study involved pH measurements and acidity constants appropriate to 20 °C, there will be systematic errors in these values. Up to 0.7 M phosphate there was no sign of second-order dependence on its concentration, and thus condensed phosphates are unlikely to be significant. In more concentrated acidic solutions at the same temperature, such condensed phosphates appear highly important , as shown by the rate law... 

Because of the chemical and steric variety of neighboring functional groups on humic and fulvic acids, there may be a range of affinities (binding energies) for metal ions and for protons, that is, a range of complex formation constants and acidity constants. 

Therefore it would be much desired to derive the concentrations and acidity constants of particular types of surface sites from some first principles, rather than to fit them as adjustable parameters. This would produce generic charging curves for certain material (rather than for specific sample). Unfortunately verification of such a model is rather difficult in view of contradictory surface charging curves reported in the literature for different samples of the same material (cf Figs. 3,43-3.73). The surface charging depends on many variables, e.g, the PZC is temperature dependent, and the absolute value of ag depends on the nature of the counterions (K versus Na, etc.). Consideration of all these variables would be very tedious, and such effects are mostly ignored in the attempts to predict the surface charging behavior of materials. 

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