Question

Arrange the following compounds in increasing order of their boiling points.

CH₃CHO, CH₃CH₂OH, CH₃OCH₃, CH₃CH₂CH₃

Answer 1

The molecular masses of the given compounds are in the range 44 to 46. CH₃CH₂OH undergoes extensive intermolecular H-bonding, resulting in the association of molecules. Therefore, it has the highest boiling point. CH₃CHO is more polar than CH₃OCH₃ and so CH₃CHO has stronger intermolecular dipole − dipole attraction than CH₃OCH₃⋅ CH₃CH₂CH₃ has only weak van der Waals force. Thus, the arrangement of the given compounds in the increasing order of their boiling points is given by:

CH₃CH₂CH₃ < CH₃OCH₃ < CH₃CHO < CH₃CH₂OH