page_title: Solvation
section_title: Solvents and intermolecular interactions
hierarchical_section_title: Solvation / Solvents and intermolecular interactions
caption_attribution_description: Deutsch: Nilrot bei Tageslicht (obere Reihe) und UV-Licht (366 nm, untere Reihe) in verschiedenen Lösungsmittels. V.l.n.r.: 1. Wasser, 2. Methanol, 3. Ethanol, 4. Acetonitril, 5. Dimethylformamid, 6. Aceton, 7. Ethylacetat, 8. Dichlormethan, 9. n-Hexan, 10. tert-Butylmethylether, 11. Cyclohexan, 12. Toluol. English: 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.
context_page_description: Solvation describes the interaction of solvent with dissolved molecules. Both ionized and uncharged molecules interact strongly with 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 the viscosity and density. In the process of solvation, ions are surrounded by a concentric shell of solvent. Solvation is the process of reorganizing solvent and solute molecules into solvation complexes. Solvation involves bond formation, hydrogen bonding, and van der Waals forces. Solvation of a solute by water is called hydration.
  Solubility of solid compounds depends on a competition between lattice energy and solvation, including entropy effects related to changes in the solvent structure.
context_section_description: Solvation involves different types of intermolecular interactions: hydrogen bonding, ion-dipole interactions, and 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.
  Solvent 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. 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 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).  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).  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.
caption: 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
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