Alkali thermodynamic parameters

Thermodynamic Parameters of the Complexation of Alkali Cations in Methanol at 25°C... 

Table 1 Kinetic and thermodynamic parameters for the conversion of compound 4 into benzo-18-crown-6 in 99% DMSO at 298.0 K and in the presence of an excessive amount of templating alkali bromide53...

The thermodynamic parameters and relative cation selectivity of some alkali and heavy metal cations with 1,5,14,18-tetraselena-8,11,21,24-tetracyclohexacosane 47 (selena-26-crown-8) were investigated for the first time by titration calorimetry in water-MeCN (l 24v/v) at 25°C to show the contrasting complexation behavior between Ag+ and alkali Tl+ and a very high Ag+ selectivity, originating from the exclusive contribution of the enthalpy term probably owing to the partially covalent interaction between Ag+ and Se-donor <1999JCM284>. 

It should be noted that the materials are synthesized under non-equilibrium conditions as the experiments are performed in a dynamic vacuum, and the local vapour pressure of the alkali metal is unknown. The rate and extent of reaction will depend on the nature of the alkali metal, the temperature of the film and the presence of residual ambient gas impurities, which are not controlled in these preliminary experiments. At present, the effect of these variables on the conductivities cannot be assessed. Synthesis in a closed system will be required to determine the relevant thermodynamic parameters. 

Table 2.2. Thermodynamic parameters of melting of some alkali metal halides...

ZrCl has a homoatomic-layer structure sequenced Cl-Zr-Zr-Cl. Each Zr atom has three neighbours in the adjacent sheet at 3.09 A, six more in the same sheet at 3.42 A and three chlorine atoms on the other side at 2.63 A. Weak chlorine-chlorine interactions between sheets at 3.61 A contrast with the strong metal-metal binding within sheets. These structural features account for the graphitic nature and anisotropic electrical conduction of ZrS. Thermodynamic parameters have been obtained for the reduction of zirconium chlorides. The reaction of ZrC with a melt containing alkali-metal chlorides and titanium chlorides has been investigated. ... 

Novozhilov et al. studied the solubility of HC1 in molten alkali- and alkaline earth metal chlorides [268, 269] and found the solubility of HC1 in these melts to obey Henry s law. The thermal dependences of the solubility (the Henry coefficient values) of HC1 in molten alkaline earth metal chlorides, which are exposed to the pyrohydrolysis, are presented in Fig. 2.5.3. The dependences are close to linear anOd their treatment by the least-squares method allows the calculation of the thermodynamic parameters of HC1 dissolution in the chloride melts. These values are presented in Table 2.5.2. 

Thermodynamic parameters of HC1 dissolution in molten alkali-metal chlorides... 

Equilibrium ion-exchange data for intermediate-silica Na-exchanged phillipsite at 25°C, in the presence of cation pairs Na/X, where X is Ba, Co, NH4, K or Ca, were collected and the relevant thermodynamic parameters were computed. Phillipsite was found very selective for Ba, K and NH4, unselective for Co, whereas only about 50% Na could be readily replaced by Ca. This behaviour was interpreted in terms of phillipsite s structural features. On the basis of the present and the previous data concerning other cations, possible applications of alkali-trachytic phillipsite-rich rocks could be envisaged in the treatment of wastewaters containing Ba, Cs, Pb and r NH4, especially if the waters are lacking K as an interfering cation. 

The thermodynamic parameters of hydration for many ions have been determined [121,125,126]. Table 3 gives the values of the standard molar Gibbs energy of hydration AGh and standard molar enthalpy of hydration AH , at 25°C for the alkali metal cations. The tabulated values are based on the respective choices A= - 1056 kj/mol and AHh(H ) = -1103 kj/mol, which result from the extrathermodynamic assumption that the thermodynamic parameters of the tetraphenylarsonium cation and tetraphen-ylborate anion are equal [127]. This reasonable and useful assumption, often... 

Table 6 Comparison of the macrocyclic effect and differences in the thermodynamic parameters for complexes of selected alkali and divalent metal ions with pentagl3raie and [ISJcrown-b."...

The enolate salts, H2C=CH(OM), have been studied at various levels of theory for all of the alkali metals. Several structural and thermodynamic parameters are reported, and the effect of the restriction of enolate resonance by attachment of the cation is described. 

Barriers to rotation around the Cca —N bonds have been determined experimentally for diaminocarbenes (3) and (4) and their protonated and lithiated counterparts the possible involvement of lithium or a proton in the dimerization of these acyclic diaminocarbenes was also reported. A computational study of the dimerization of diaminocarbenes has been performed via rate constant calculations using general transition-state theory calculations. Such a dimerization has been shown to be a rapid equilibrium between the carbenes and the tetra-A-alkyl-substituted enetetramines (5), by characterization of metathesis products when two different tetramines were mixed. The thermodynamic parameters of this Wanzlick equilibrium have been determined for the A-ethyl-substituted compound the enthalpy of dissociation has been evaluated at 13.7kcalmol and the entropy at 30.4calmor K . Complex-ation of diaminocarbenes by alkali metals has been clearly established by a shift of the C NMR signal from the carbene carbon of more than 5 ppm. ... 

Morf, W. E., and Simon, W., Thermodynamic parameters of the ring compounds-alkali complexes in aqueous solvent, Helv. Chim. Acta, 54, 794, 1971. 

The nonnuclear chemistry of Fr reduces to studies of coprecipitation in which Fr shows the behavior of the heavier alkali metal. Coprecipitation is followed by ion exchange to concentrate Fr Physical (mp, density, crystal parameters) and chemical (thermodynamics, solvation entropies) properties are theoretically derived or extrapolated from the trends exhibited by the other alkali metals. 

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