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.

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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.

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Cholesterol is insoluble in water.

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

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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.

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