Hydrogen bonding
Hydrogen bonding is an example of a dipole - dipole interaction in which a hydrogen atom acts as a “bridge” between two very electronegative atoms. This attractive force is ~20 kJ/mol.
Ethanol (CH3 CH2 OH) and dimethyl ether (CH3 OCH3 ) have the same molecular formula.
However ethanol has a boiling point of 78.3°C whereas that of the ether is -24.8°C.