Competitive solvation

In this section we study the competitive solvation of PVA in ethanol-water mixture. For this propose the concept of local atomic fractions, defined as follow, has been used by Mtiller-Plathe and van Gunsteren [79]... 

Early mass-spectrometer studies (Hogg and Kebarle, 1965 Hogg et al., 1966 Searles and Kebarle, 1968), confirmed later by different groups and techniques (Payzant et al., 1973 Fehsenfeld and Ferguson, 1973 Tang and Casdeman, 1975) of the competitive solvation of NHa by water and ammonia vapors had shown that NHs molecules were taken up preferentially to water, up to an addition of four molecules in the first solvation shell, while water seemed to be preferred over ammonia in the second solvation shell. 

Relatively little is known about competitive solvation in mixtures of nonaqueous solvents. Complex formation between Na+ and THF in solutions of Na+[AlBu4] in hexane at molar ratios 1 1 (solvated contact ion pair) and 1 4 (solvent-separated ion pair) was reported by Schaschel and Day with proton NMR as well as IR and conductivity measurements (83, 84). Preferential solvation of alkali metal ions by DMSO in 1-pentanole and by acetone in nitromethane was observed by Popov et al. 69, 85). 

Competitive Solvation in the Gas Phase. by Water and Methanol and by Water and Ammonia Molecules... 

In a benzene and ethylacetate (7 3) mixture, ethylacetate should be the predominant solvent over benzene, even if benzene can form hydrogen bonds with the polar groups of triterpene, and even if these solvents are classified similarly, because the ethylacetate (proton donor property) value (2.0) is higher than that of benzene (0.5). The correlation coefficient for log k is less than that of log k2 because benzene is also a weak proton donor solvent and contributes to desorption. It is difficult, however, to quantitatively analyze such competitive solvation. After adding the electrostatic energy values of the carbo)yl group, the correlation coefficient increased ... 

Wang, Y. X. Balbuena, R B., Combined Ab Initio Quantum Mechanics and Classical Molecular Dynamics Studies of Polyphosphazene Polymer Electrolytes Competitive Solvation of Li+ and liCFaSOj. J. Phys. Chem. B 2004,108, 15694-15702. 

As discussed above, recent work has established the utility of the flowing afterglow technique for studying competitive solvation reactions of the type usually studied in high-pressure mass spectrometers as described in Chapter 7. From the observation that the reaction... 

The cross-linking behavior was influenced by the solvent properties. The competitive solvation of o-dichlorobenzene (relative to toluene) weakened the host-guest interaction, causing host 18 to be unable to create stable cross-linkages with poly-1. 

Kebarle has given an excellent summary [9] of his important studies on the energetics of attachment of solvent molecules to ions in the gas phase. These studies include successive hydrations of alkali ions, halide ions and hydrogen ion competitive solvations of hydrogen ion by water, methanol, and ammonia and competitive solvations of chloride ion by various molecules, such as benzene, water, alcohols, aniline, acetonitrile, and phenol. In this section a very brief discussion is given of the results of preliminary studies of equilibria which appear to be of the types represented by equations 7,8,9, and 10 below. 

PRF-23 and PRF-24 demonstrate a novel way to create PRFs by using permanently interlocked rotaxanes which are connected by a mechanical linkage and not merely held together by relatively weak non-covalent interactions prior to PRF synthesis. This synthetic approach allows for the use of harsher reaction conditions since the linker cannot simply unthread when exposed to competitive solvation during PRF formation. 

Wang, Y., Balbuena, P. B., Combined ab initio quantum mechanics and classical molecular dynamics studies of polyphosphazene polymer electrolytes Competitive solvation of LR and LiCFjSO, The Journal of Physical Chemistry B, 2004, 108, 15694-15702. 

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