Hydrophobic hydration destruction

From an analysis of the hydrophobic-induced pKa and reduction potential shifts with the associated destruction of hydrophobic hydration on formation of carboxylates (see Figure 5.25B), we argue that the solvation limitation of phosphates can be made critical by the competition for hydration between polar and hydrophobic domains. 

Question Over What Distances Can such Destruction of Hydrophobic Hydration Be Effective ... 

Main sources of the increase in entropy may be also the destruction of the hydrophobic hydration and an increase in the freedom of molecular motion,rotational and so-called configurational,of alcohols in the cavities. The large increments of entropy with 3-CD suggest the enhanced contribution of the latter and the additional increments in so-called communal entropy accompanied by the exchange of included water molecules for an alcohol molecule. 

As stated above, the hysteresis of ELPs in the course of the ITT transition results from the overlap of two kinetically different processes a fast endothermic process, which corresponds to the destruction of the ordered hydrophobic hydration, and a second exothermic process arising from the P-spiral chain folding. 

In the previous section we have seen that the formation of hydrophobic hydration shells aids the dissolution of apolar solutes in water. Upon increasing concentration and/or size of the solute it is inevitable that, at a critical concentration, the large hydrophobic hydration shells start to overlap, leading to mutually destructive breakdown of these water arrangements (Fig. 2.6). This sacrifice of H-bonding interactions results in a solvent-induced sticking... 

Figure 2.6 Hydrophobic interactions. Cartoon of the destructive overlap of two hydrophobic hydration shells (striped areas) resulting in a release of water to the bulk solution.

Thus different parts of the molecule may carry hydration shells that have significantly different properties. This leads to mutually destructive intramolecular overlap of water shells and the resulting overall hydration characteristics will definitely represent these complexities. This makes it difficult to define hydrophobic parameters for organic functional groups because they will depend on their position in the molecule. Only long alkyl functionalities do not suffer from these overlap effects. Recent kinetic studies have demonstrated these effects and rough estimates have been made of the extent of the overlap region in the total hydration shell vide supra). 

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