Step 1: Understanding the Question:
The boiling point of organic compounds depends on the strength of intermolecular forces. In this set, we have a ketone, an alcohol, a carboxylic acid, and an aldehyde.
Step 2: Detailed Explanation:
- Propanone and Propanal: These exhibit dipole-dipole interactions, which are relatively weak.
- Propan-1-ol: It has strong intermolecular hydrogen bonding.
- Ethanoic acid: It also exhibits hydrogen bonding, but it is even stronger because carboxylic acids can form stable cyclic dimers. Each molecule is involved in two hydrogen bonds with another.
As a result, carboxylic acids have higher boiling points than alcohols of comparable molecular mass.
Even though propan-1-ol (\( M \approx 60 \)) and ethanoic acid (\( M \approx 60 \)) have similar molecular weights, the carboxylic acid's dimers lead to much higher boiling points.
Step 3: Final Answer:
Ethanoic acid has the highest boiling point among the listed compounds.