Solvation
Both ionized and uncharged molecules interact strongly with a solvent, and the strength and nature of this interaction influence many properties of the solute, including solubility, reactivity, and color, as well as influencing the properties of the solvent such as its viscosity and density.
[2] Solubility of solid compounds depends on a competition between lattice energy and solvation, including entropy effects related to changes in the solvent structure.
[citation needed] Solvation involves different types of intermolecular interactions: Which of these forces are at play depends on the molecular structure and properties of the solvent and solute.
[5] Water is the most common and well-studied polar solvent, but others exist, such as ethanol, methanol, acetone, acetonitrile, and dimethyl sulfoxide.
Some chemical compounds experience solvatochromism, which is a change in color due to solvent polarity.
Other solvent effects include conformational or isomeric preferences and changes in the acidity of a solute.
A negative Gibbs energy indicates a spontaneous process but does not provide information about the rate of dissolution.
This is both entropically and enthalpically unfavorable, as solvent ordering increases and solvent-solvent interactions decrease.
Stronger interactions among solvent molecules leads to a greater enthalpic penalty for cavity formation.
Gases have a negative entropy of solution, due to the decrease in gaseous volume as gas dissolves.
A negative value for the enthalpy change of solution corresponds to an ion that is likely to dissolve, whereas a high positive value means that solvation will not occur.
[8] Although early thinking was that a higher ratio of a cation's ion charge to ionic radius, or the charge density, resulted in more solvation, this does not stand up to scrutiny for ions like iron(III) or lanthanides and actinides, which are readily hydrolyzed to form insoluble (hydrous) oxides.
One way to compare how favorable the dissolution of a solute is in different solvents is to consider the free energy of transfer.
Recent simulation studies have shown that the variation in solvation energy between the ions and the surrounding water molecules underlies the mechanism of the Hofmeister series.
For instance, solvation of ions and/or of charged macromolecules, like DNA and proteins, in aqueous solutions influences the formation of heterogeneous assemblies, which may be responsible for biological function.
[11] Minimizing the number of hydrophobic side chains exposed to water by burying them in the center of a folded protein is a driving force related to solvation.
[13][14] Due to the importance of the effects of solvation on the structure of macromolecules, early computer simulations which attempted to model their behaviors without including the effects of solvent (in vacuo) could yield poor results when compared with experimental data obtained in solution.
