Hydration energetics

Indeed, some relationships between AVf, AH, and AS have been found for enzyme reactions. In the works of Somero and collaborators, these relationships have been interpreted in terms of salt effects on hydration energetics in the activation process. 

Hydrophilic hydration signifies that a strong energetically favored direct interaction exists between dissolved polar or ionic particle and the surrounding water molecules by ion-dipole-, dipole-dipole-interactions and/or hydrogen bonds. 

Support for the involvement of Fe comes from the observation that the kinetic chain length of the dimethyl ester increases with increasing concentration of added Fe together with a fourfold increase in the yield of 262 (216). However, as a vinyl cation bearing carbonyl substituents may be energetically unfavorable, an alternative mechanism, involving a ligand transfer from hydrated Fe ions followed by an acid-catalyzed cyclization, may be a more likely pathway ... 

Pratt, L. R., Rempe, S. B., Topol, I. A., and Burt, S. K. (2000). Alkali metal ion hydration and energetics of selectivity by ion-channels. Biophys.J. 78, P2057-P2057. 

Rowley, A. T. et al., Inorg. Chem. Acta, 1993, 211(1), 77 Preparation of metal oxides by fusing metal halides with lithium oxide in a sealed tube leads to explosions if halide hydrates are employed, particularly lanthanide trihalide hydrates. The preparation succeeds with anhydrous halides. This will be purely a question of vapour pressure above an exothermic reaction the question is whether the vapour is water, or metal halide, and the reaction oxide formation, or hydration of lithium oxide. Like other alkali metal oxides, hydration is extremely energetic. 

By contrast, anions have larger radii and tend to be more weakly hydrated. In addition, they are able to form relatively strong ionic/covalent bonds to the surface of the metal electrode and, as a result, frequently find it energetically feasible to shed their inner hydration sphere, or at least part of it, and adsorh directly on the surface. The plane formed hy the nuclei of anions directly adsorbed on the metal surface is termed the inner Helmholtz plane (IHP). 

The hydration enthalpy of the Al3+ ion is enormous (-4690k) mol-1), and there are some interesting effects produced as a result. When NaCl is dissolved in water and the solvent evaporated, the solid NaCl can be recovered. If A1C13 is dissolved in water, evaporation of the water does not yield the solid A1C13. The Al3+ ion is so strongly solvated that other reactions become energetically more favorable than removing the solvent. This can be shown as follows. 

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