Polarity
A popular aphorism used for predicting solubility is "like dissolves like". This statement indicates that a solute will dissolve best in a solvent that has a similar chemical structure to itself. This view is simplistic, but it is a useful rule of thumb. The overall solvation capacity of a solvent depends primarily on its polarity. For example, a very polar (hydrophilic) solute such as urea is very soluble in highly polar water, less soluble in fairly polar methanol, and practically insoluble in non-polar solvents such as benzene. In contrast, a non-polar or lipophilic solute such as naphthalene is insoluble in water, fairly soluble in methanol, and highly soluble in non-polar benzene.
The solubility is favored by entropy of mixing and depends on enthalpy of dissolution and the hydrophobic effect.
Synthetic chemists often exploit differences in solubilities to separate and purify compounds from reaction mixtures, using the technique of liquid-liquid extraction.
Read more about this topic: Solubility
Famous quotes containing the word polarity:
“The same polarity of the male and female principle exists in nature; not only, as is obvious in animals and plants, but in the polarity of the two fundamental functions, that of receiving and penetrating. It is the polarity of earth and rain, of the river and the ocean, of night and day, of darkness and light, of matter and spirit.”
—Erich Fromm (1900–1980)