Arrange the isomeric compounds:
(i) Ethyldimethyl amine
(ii) n-butyl amine
(iii) diethyl amine
in order of decreasing boiling point and give reason.

The correct order is II > III > I
(II) is a 1° amine (III) is 2° amine and can associate via intermolecular hydrogen bonding. But 1° amine has two H present at N-atom, therefore, more hydrogen bonding. Hence, (II) has a higher boiling point than (III)
(I) is a 3° amine, there is no H present on N atom, no H-bonding present. Hence, (I) has a lowest boiling point.