The molecular masses of these compounds are in the range of 72 to 74. Since only n-butanol molecules are associated due to extensive inter-molecular hydrogen bonding, therefore, the boiling points of n-butanol would be the highest. Butanal is more polar than ethoxy ethane. Therefore, the intermolecular dipole-dipole attraction is stronger in the former. The p-pentane molecules have only weak Van der Waals forces. In view of the above facts the following compounds are arranged as per their increasing order of boiling points.

CH₃CH₂CH₂CH₂CH₃<H₅C₂—O-C₂H₅ < CH₃CH₂CH₂CHO < CH₃CH₂CH₂CH₂OH