How does water dissolve organic molecules?

1 Answer
Jun 5, 2015

Water dissolves organic molecules by forming dipole-dipole attractions and hydrogen bonds with them.

The simple rule is, "Like dissolves like".

In other words, molecules that are polar will dissolve in a polar solvent like water.

A molecule like cholesterol consists almost entirely of nonpolar C-C and C-H bonds.

Most of its attractive forces are weak London dispersion forces.

The water molecules attract each other so strongly that a cholesterol molecule can't get between them.

Cholesterol is insoluble in water.

Glucose, on the other hand, has many polar OH groups that can form hydrogen bonds to water.

The water molecules are attracted to the glucose as strongly as they are to each other.

Glucose can easily get between the water molecules, so glucose dissolves in water.

Generally, the more O-H and N-H groups in a molecule, the more soluble it will be.