Final answer:
The boiling points of the compounds from highest to lowest are benzoic acid, 2-butyne, propane, and methane, respectively. Benzoic acid has the highest boiling point due to strong hydrogen bonding, while methane has the lowest due to weak dispersion forces.
Step-by-step explanation:
To rank the boiling points of the given compounds — 2-butyne, benzoic acid, methane, and propane — we need to consider the types and strengths of intermolecular forces present in each compound.
Methane is a simple alkane with only London dispersion forces, and due to its small size, it has a low boiling point. Propane is similar but slightly larger, giving it a somewhat higher boiling point.
2-butyne is an alkyne with a linear shape, which allows for more surface contact and thus stronger London dispersion forces than in smaller gases like methane and propane.
However, benzoic acid has the highest boiling point due to its ability to form strong hydrogen bonds, which are significantly stronger than the dispersion forces present in alkanes and alkynes.
The correct order from the highest to the lowest boiling points is: benzoic acid > 2-butyne > propane > methane.