Question

Select from each of the following sets the hydrocarbons having the lowest and highest boiling point:

n-pentane, n-hexane, 2,3-dimethyl butane

Answer 1

Boiling point $\propto$ Molecular weight

Boiling point $\propto$ Branching.

Of n-pentane, n-hexane and 2,3-dimethyl butane. n-pentane has the lowest mass and 2,3-dimethyl butane has the highest mass same as that of n-hexane but 2,3-dimethyl butane has higher branching than n-hexane.

So, the order of boiling point is

2,3-dimethyl butane > n-hexane > n-pentane

Hence, hydrocarbon with the highest boiling point is 2,3-dimethyl butane and that with the lowest boiling point is n-pentane.