Question

Explain why propanol has higher boiling point than that of the hydrocarbon, butane?

Answer 1

Although butane and propanol have comparable molecular masses (58 and 60 respectively) but, in propanol, polar -OH group is present, due to which strong intermolecular hydrogen bonding exists between its molecules. Whereas in butane weak van der Waals' forces of attraction are the only forces between the molecules.Therefore propanol has higher boiling point (391 K) as compared to that of butane (309 K).

$\dots \dots \stackrel{{\delta }^{+}}{H}-\stackrel{{\delta }^{-}}{\underset{C_3{H}_7}{\underset{|}{O}}}\dots \dots \stackrel{{\delta }^{+}}{H}-\stackrel{{\delta }^{-}}{\underset{C_3{H}_7}{\underset{|}{O}}}\dots \dots \stackrel{{\delta }^{+}}{H}-\stackrel{{\delta }^{-}}{\underset{C_3{H}_7}{\underset{|}{O}}}\dots \dots$