How do covalent bonds dissolve in water?

1 Answer

Covalent bonds do not dissolve in water, but some covalent compounds do.

Covalent molecules are attracted to each other by various intermolecular forces such as H-bonds, dipole-dipole forces, and London dispersion forces. Water molecules are attracted to each other by strong H-bonds.

A polar solute may be attracted to the water molecules as strongly as the water molecules are attracted to each other.

It should contain a highly electronegative atom such as N or O or, even better, an N-H or an O-H bond, because they can form H-bonds to the water molecules. It will then be able to work its way among the water molecules (dissolve).

Sugar and ethanol are covalent compounds that are soluble in water, because they contain O-H groups that can H-bond to the water.

Nonpolar compounds like hydrocarbons have weak intermolecular attractive forces.

For example, hexane, C₆H₁₄, does not dissolve in water. Its molecules have little attraction to each other or to the water molecules.

The water molecules, on the other hand, are strongly attracted to each other. They stick together and keep out most of the hexane molecules.