Editing Solvation (section)

== Solvents and intermolecular interactions ==
Solvation involves different types of intermolecular interactions: 

* Hydrogen bonding
* Ion–dipole interactions
* The van der Waals forces, which consist of dipole–dipole, dipole–induced dipole, and induced dipole–induced dipole interactions. 

Which of these forces are at play depends on the molecular structure and properties of the solvent and solute. The similarity or complementary character of these properties between solvent and solute determines how well a solute can be solvated by a particular solvent.

[[File:Nile red 01.jpg|thumb|[[Nile red]] at daylight (top row) and UV-light (second row) in different solvents. From left to right: 1. Water, 2. Methanol, 3. Ethanol, 4. Acetonitrile, 5. Dimethylformamide, 6. Acetone, 7. Ethylacetate, 8. Dichlormethane 9. n-Hexane, 10. Methyl-tert-Butylether, 11. Cyclohexane, 12. Toluene. Photographer: Armin Kübelbeck, CC-BY-SA, Wikimedia Commons]]

Solvent [[Chemical polarity|polarity]] is the most important factor in determining how well it solvates a particular solute. Polar solvents have molecular dipoles, meaning that part of the solvent molecule has more electron density than another part of the molecule. The part with more electron density will experience a partial negative charge while the part with less electron density will experience a partial positive charge. Polar solvent molecules can solvate polar solutes and ions because they can orient the appropriate partially charged portion of the molecule towards the solute through electrostatic attraction. This stabilizes the system and creates a [[solvation shell]] (or hydration shell in the case of water) around each particle of solute. The solvent molecules in the immediate vicinity of a solute particle often have a much different ordering than the rest of the solvent, and this area of differently ordered solvent molecules is called the cybotactic region.<ref name="Anslyn & Dougherty">Eric V. Anslyn; Dennis A. Dougherty (2006). Modern Physical Organic Chemistry. University Science Books. {{ISBN|978-1-891389-31-3}}.</ref> Water is the most common and well-studied polar solvent, but others exist, such as [[ethanol]], [[methanol]], [[acetone]], [[acetonitrile]], and [[dimethyl sulfoxide]]. Polar solvents are often found to have a high [[dielectric constant]], although other solvent scales are also used to classify solvent polarity. Polar solvents can be used to dissolve inorganic or ionic compounds such as salts. The [[Electrical resistivity and conductivity|conductivity]] of a solution depends on the solvation of its ions. Nonpolar solvents cannot solvate ions, and ions will be found as ion pairs.

Hydrogen bonding among solvent and solute molecules depends on the ability of each to accept H-bonds, donate H-bonds, or both.  Solvents that can donate H-bonds are referred to as protic, while solvents that do not contain a polarized bond to a hydrogen atom and cannot donate a hydrogen bond are called aprotic.  H-bond donor ability is classified on a scale (α).<ref>{{cite journal | author = Taft R. W., Kamlet M. J. | year = 1976 | title = The solvatochromic comparison method. 2. The .alpha.-scale of solvent hydrogen-bond donor (HBD) acidities | journal = J. Am. Chem. Soc. | volume = 98 | issue = 10| pages = 2886–2894 | doi = 10.1021/ja00426a036 | bibcode = 1976JAChS..98.2886T }}</ref>  Protic solvents can solvate solutes that can accept hydrogen bonds.  Similarly, solvents that can accept a hydrogen bond can solvate H-bond-donating solutes.  The hydrogen bond acceptor ability of a solvent is classified on a scale (β).<ref>{{cite journal | author = Taft R. W., Kamlet M. J. | year = 1976 | title = The solvatochromic comparison method. 1. The .beta.-scale of solvent hydrogen-bond acceptor (HBA) basicities | doi = 10.1021/ja00418a009 | journal = J. Am. Chem. Soc. | volume = 98 | issue = 2| pages = 377–383 | bibcode = 1976JAChS..98..377K }}</ref>  Solvents such as water can both donate and accept hydrogen bonds, making them excellent at solvating solutes that can donate or accept (or both) H-bonds.

Some chemical compounds experience [[solvatochromism]], which is a change in color due to solvent polarity. This phenomenon illustrates how different solvents interact differently with the same solute. Other [[solvent effects]] include conformational or isomeric preferences and changes in the acidity of a solute.