The boiling point of propanoic acid is higher than that of 1-butanol due to the prevalence of hydrogen bonding in propanoic acid.
Hydrogen bond forms as a result of the electrostatic attraction between the hydrogen of one molecule and a more electronegative specie on another molecule(N or O or F).
In propanoic acid, the hydrogen bonding is more pronounced and strong.
For 1-butanol, the bonding is weak and not strong.
