Water Solubility

Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a liquid solvent to form a homogeneous solution. The solubility of a substance strongly depends on the used solvent as well as on temperature and pressure. The extent of the solubility of a substance in a specific solvent is measured as the saturation concentration where adding more solute does not increase the concentration of the solution.
The solubility of a given solute in a given solvent typically depends on temperature. For many solids dissolved in liquid water, the solubility increases with temperature up to 100 °C


More details

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Examples

 

Soluble Insoluble
o organic salts (RCO2-Na+ & NR4+Cl-) o saturated hydrocarbons
o monofunctional alcohols (ROH) o unsaturated hydrocarbons
o esters (RCO2R‘) o aromatic hydrocarbons
o ethers (ROR‘) o alkyl halides
o acids (RCO2H) o aryl halides
o amines (NR3)
o nitriles (RCN)
o amides (RC(O)NH2)
o ketones (RC(O)R‘)
o aldehydes (RCHO)
o etc…(all less than five carbons)

Notes:

  1. In most homologous series of the above types of compounds, the longest chain with appreciable water solubility will be reached at about five carbons.
  2. Introduction of a halogen will usually lower the solubility.
  3. A benzene ring approximates 4 aliphatic carbons.
  4. Position of functional group, branching, and the compactness of the molecule will affect solubility:

o functional group toward center of molecule – increased water solubility
o increase in the number of branches – increased water solubility
o more compact molecular shape – increased water solubility