Arrange the following compounds in increasing order of boiling point.

Propan-1-ol, butan-1-ol, butan-2-ol, pentan-1-ol

The boiling points of alcohols and phenols increase with an increase in the number of carbon atoms. This is because of the increase in van der Waals forces.

In alcohols, the boiling points decrease with the increase of branching in the carbon chain because of the decrease in van der Waals forces with a decrease in surface area.

Thus b.p increases with a number of carbon atoms in the chain and for the same number of atoms, it depends on branching as in the case of butan-2-ol and butan-1-ol.