The key thing to consider here is that boiling points reflect the strength of forces between molecules. The more they stick together, the more energy it will take to blast them into the atmosphere as gases. ... Boiling points increase as the number of carbons is increased. Branching decreases boiling point.

What is effect of branching on boiling point?

As the branching is done in an alkane its surface area decreases, this results in decrease of boiling point and increase in melting point, so we can say that surface area ∝ melting point.

Why does less branching mean higher boiling point?

As branching increases, the surface area of the molecule decreases which results in a small area of contact. As a result, the Van der Waals force also decreases which can be overcome at a relatively lower temperature. Hence, the boiling point of an alkane chain decreases with an increase in branching.