Amines are polar compounds and with the exception of tertiary amines can form intermolecular hydrogen bonding. As a result amines have higher boiling points.
Among the isomeric amines the primary and secondary amines have highest boiling point due to formation of H-bonds. Whereas tertiary amines have lowest boiling point because of their inability to form H-bonds. The boiling point of primary amine is greater than secondary.
But in NH2CH2CH2NH2 two amine groups are attached on both side therefore, H-bonding is maximum in this compound. Hence, its boiling point is highest.
