Boiling points of three isomeric pentanes are `36.2^@C ,28^@C and 9.5^@C` respectively. Identify the compounds and give reason.

Explanation

Strength of van der Waals forces depends on the area of contact between molecules. Area of contact between straight chain n-pentane `(CH_3CH_2CH_2CH_2CH_3)` molecules is maximum. So, the extent of van der Waals' attraction among its molecules is maximum. For this reason , its boiling point is highest `(36.2^@C)` . On the orther hand , area of contact between spherical neopentane `[(CH_3)_4C]` molecules is minimum. So, the extent of van der Waals' attraction among its molecules is the minimum . For this reason , its boiling point is the lowest `(9.5^@C)` . Again, the area of contact between isopentane `[(CH_3)_2CHCH_2CH_3]` molecules is intermediate between n-pentane and neopentane and so, its boiling point `(28^@C)` is intermediate between the other two isomers.