Alkali metal and halide ions

Hybrid solvation Implicit solvation plus Explicit solvation microsolvation subjected to the continuum method. Here the solute molecule is associated with explicit solvent molecules, usually no more than a few and sometimes as few as one, and with its bound (usually hydrogen-bonded) solvent molecule(s) is subjected to a continuum calculation. Such hybrid calculations have been used in attempts to improve values of solvation free energies in connection with pKp. [42], and also [45] and references therein. Other examples of the use of hybrid solvation are the hydration of the environmentally important hydroxyl radical [52] and of the ubiquitous alkali metal and halide ions [53]. Hybrid solvation has been surveyed in a review oriented toward biomolecular applications [54]. 

Tracey, A.S. and T.L. Boivin. 1984. Interaction of alkali metal and halide ions in lyotropic liquid crystalline solution. J. Phys. Chem. 88 1017-1023. 

In order to simplify the determination of free energies of transfer, Covington et deduced a relation between AG and the chemical shifts of ions. It is well known that the chemical shift of alkali metal and halide ions in mixed solvents e.g. 

Hydration Numbers for Some Alkali Metal and Halide Ions Obtained from MD Calculations and X-Ray and Neutron-Diffraction Experiments ... 

One of the most widely known and used set of ionic radii are those estimated by Pauling [2] on the basis of interionic distances in ionic crystals. He noted that repulsive effects between ions of the same charge depend on the relative size of the cation and anion in the crystal, and also took into consideration the coordination number of the ion with oppositely charged neighbors in the crystal lattice. The results obtained for the alkali metal and halide ions for the case that the coordination number is six (rock salt structure) are summarized in table 3.1. 

Table 3.1 Radii for the Alkali Metal and Halide Ions for a Coordination Number of Six Estimated from Crystallographic Data Together with Ion-Oxygen Atom Distances from Diffraction Studies of Aqueous Solutions...

Table II. Bulk Solution Free Energy of Solvation for Alkali Metal and Halide Ions In Methanol Solutions...

Figure 3. Born Equation for alkali metal and halide ions—bulk-phase free energy of solvation in methanol solutions...

As we have already mentioned, liquid NH3 undergoes self-ionization (equation 8.12), and the small value of Aijeif (Table 8.4) indicates that the equilibrium lies far over to the left-hand side. The [NH4] and [NH2] ions have ionic mobilities approximately equal to those of alkali metal and halide ions. This contrasts with the situation in water, in which [H30]+ and [OH] are much more mobile than other singly charged ions. 

Equation 5 predicts that the viscosity B coeflBcient should increase with increasing ion size and should be independent of temperature and solvent inasmuch as the ionic size is temperature and solvent independent. The data for the alkali metal and halide ions (24) in Table I and for the tetraalkylammonium bromides (28) in Figure 4 show that neither of the predictions is verified by experiment. 

Nearly all the ions show some temperature dependence in aqueous solution, but at least for the tetraalkylammonium ions, very little in methanol solutions (Figure 4). Instead of increasing, B decreases with increasing size for the alkali metal and halide ions. The negative values of B indicate that most of these ions actually decrease the viscosity upon their addition to water. The B coefficients for the tetraalkylammonium ions increase with increasing size but for the larger ions, B is much larger in aqueous than in methanol solutions and extremely temperature dependent in aqueous solution. 

The terms structure making and structure breaking are attributed to Gurney (1953), but Cox and Wolfenden (1934) were the first to mention the notion of water structure in the connection of the viscosities. Furthermore, Frank and Evans (1945) have already used the term structure breaking (but not -making ) with regard to effects of the alkali metal and halide ions, except Li+ and F , on the partial molar entropies of dilute aqueous solutions. The Jones-Dole -coefficient, Eq. (2.35), is the quantitative measure of this effect, and this equation may be recast in the form ... 

The unusual mole fraction scale for the solution, with 5 x(H+,aq) = -68.2 J mol was used for the calculation of values of Astmc5 for the alkali metal and halide ions as well as Ag+ and CIO4 (Abraham et al. 1982). However, the choices of the value of 5 (H+, aq) and the mole fraction scale caused K+ to appear as a strue-ture making ion. This unacceptable result is corrected by adjustment to the molar scale with 5° (H+, aq) = - 22.2 J mol. Linear correlations of Astmc5 with the viscosity coefficients and with the NMR coefficients (Sect. 3.1.3) and also with the ionic partial molar volumes or their electrostricted volumes were noted by Abraham et al. (1982). 

The dependence of K ec eluant pH for alkali metal and halide ions on... 

Lee, S. H., and Rasaiah, J. C. 1996. Molecular dynamics simulation of ion mobility. 2. Alkali metal and halide ions using the SPC/E model for water with simple truncation of ion-water potential. J. Phys. Chem. 100 1420. 

A further measure of the sizes of ions, pertaining to ions in solution, is their intrinsic molar volumes, The molar volume of a bare unsolvated ion, 4jrNJ3)r, cannot represent the intrinsic volume of the ion in solution, because of the void spaces between the solvent molecules and the ion and among themselves. Mukerjee [52] proposed for aqueous alkali metal and halide ions at 25°C a factor of A = 1.213, producing ... 

Ions. There was extensive early work on concentration shifts for alkali-metal and halide ion resonances. These are strongly dependent upon salt concentration and on the nature of the gegen ions [23]. Clearly, dehydration and ion pairing are both involved in these shifts, which tend toward the pure salt values. However, no firm structural information has been forthcoming. 

Good, W., and Wood, J. E., 1971a, The hydrational effect of alkali metal and halide ions on the Rh-anti-Rh system. Immunology 90 37. 

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