Therefore, the intermolecular dipole-dipole attraction
is stronger in the former n-Pentane molecules have only weak van
der Waals forces Hence  increasing order of boiling points  of the
given compounds is as follows:
CH3CH2CH2CH3 < H5C2-O-C2H5 < CH3CH2CH2CHO < CH3CH2CH2CH2OH
Example 8 2
Example 8