91Ó°ÊÓ

The boiling point is affected by van-der-Waal forces:

The van-der-Waal forces increase as the non-polar carbon molecules are bonded. Therefore, with the increase in the chain of the carbon length, the boiling point increases due to the presence of van-der-Waals forces

The boiling point is affected by hydrogen bonding:

The boiling point increases as the extent of the hydrogen bonding increases.

For alcohols with the same number of carbon atoms: hydrogen bonding and boiling point increase in the order as shown: $3°\mathrm{OH}<2°\mathrm{OH}<1°\mathrm{OH}$

a. The boiling point increases with the increase in hydrogen bonding due to the presence of an oxygen atom.

Order of boiling point

b. The branching of the same carbon length decreases the van-der-Waals forces of attraction. Therefore, the boiling point increases with the decrease in the chain.

Order of boiling point