Free enthalpy of ionization

Calculate AS° for ionization of each compound. Comment on the contribution of AH° and AS° to the free energy of ionization. Test the data for linear fiee-energy correlations. Are the linear free-energy correlations dominated by entropy or enthalpy terms ... 

Table 18 shows the free energies and enthalpies of ionization of some nitroalkanes. 

Fig. 3-8. Energy for formation of the standard gaseous ions, S(Vnj), from the surface atoms of a semiconductor of single element S dGnbi = standard free enthalpy of the surface atom sublimation h = ionization energy of gaseous atoms aj. = unitary level of the surface ion = - (dGsM + /s) = unitary level of the surface atom referred to the standard gaseous ions and elections.

D. Free Energies and Enthalpies of Ionization in Aqueous Solution.201... 

The enthalpies of ionization corresponding to Eqs. (4), (3"), and (11) can be determined by means of the temperature effect on the respective standard free energy changes (70MI3) or by calorimetric techniques. 

State-of-the-art calorimetry allows the accurate determination of enthalpies and free energies of ionization with micromolar amounts of weak acids and bases. The acidic pKs as well as the neutralization enthalpies of imidazole and pyrazole have been determined by calorimetry. 

In view of the occurrence of electron transfer and also in view of the observations made by Bryce-Smith and Gilbert (on which the ionization potential rule is based), Mattay et al. [15,143,144] have proposed a relationship between the mode of reaction (ortho addition, meta addition, substitution) and the free enthalpy of electron transfer between the reaction partners. The free enthalpy was calculated using the Rehm-Weller equation... 

From the pKa values, the following sequence of 2-substituted 4-thiazolidinones with respect to the degree of acidity are 5 > 2 > 3.186 The opening of the thiazolidinone ring leads to an increase in acidity, but does not affect the activity sequence of the substituents.186 The acidity of a series of substituted 5-benzylidene-2,4-thiazoIidinediones has been investigated the entropy, enthalpy, and free energy of ionization have been calculated.187 Potentiometric determination of the tautomeric equilibrium constants of various 4-thiazolidinones has been reported.188... 

Johnson, F.A., Lewis, S.D., Shafer, J.A. (1981). Perturbations in the free energy and enthalpy of ionization of histidine-159 at the active site of papain as determined by fluorescence spectroscopy. Biochemistry 20 52-8. 

The oxygen vacancies formed at elevated temperatures and low oxygen partial pressure are assumed to be doubly ionized. The thermally activated charge disproportionation reaction given by Eq. (10.51) reflects the localized nature of electronic species and may be treated as equivalent to the generation of electrons and electron holes by ionization across a pseudo band gap cf. Eq. (10.27)). The associated free enthalpy of reaction may be taken equal to the effective band gap energy. 

AG°o,v(Ar) and AG°oiv(Ar ) are the free energies of solvation of the neutral molecule and the radical cation, respectively, and F is the Faraday constant. It should be noted that the ionization potential is the enthalpy of ionization at 0 K thus, the ionization entropy and the temperature correction are neglected in equation (3). However, these corrections are assumed to be fairly small. 

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