Properties of alcohols
Compared with alkanes, alcohols have significantly higher boiling points. The hydroxyl groups in alcohol molecules are responsible for hydrogen bonding between the alcohol molecules.
As greater energy is required to overcome these strong intermolecular forces, the melting points and boiling points of alcohols are higher than those of alkanes with a corresponding chain length.
Alcohols with a greater number of hydroxyl groups will have even higher boiling points. When an alcohol has two hydroxyl groups it is called a diol. A molecule with three hydroxyl groups is a triol.
Compare these three molecules:
The large increase in the boiling point of alcohols as the number of hydroxyl groups increases is caused by a greater degree of hydrogen bonding between the molecules.