Concept:Carboxylic acids show the highest boiling point due to strong intermolecular hydrogen bonding between their molecules.
Explanation:The
−COOH group contains a highly polar
O−H bond, which enables strong hydrogen bonding.
Two carboxylic acid molecules join together to form a stable dimer:
2RCOOH⇌(RCOOH)2​This dimer is held by two intermolecular hydrogen bonds, making the attraction very strong.
Extra heat energy is required to break these bonds during boiling, so the boiling point becomes highest.
Alkanes and ethers have only weak van der Waals forces, which are much weaker than hydrogen bonds.
Alcohols and aldehydes also form hydrogen bonds, but carboxylic acids form stronger dimeric hydrogen bonding.
Formation of carboxylate ions is related to acid-base reactions, not to the boiling point.
Intramolecular hydrogen bonding occurs within the same molecule, whereas carboxylic acids mainly show intermolecular hydrogen bonding.
Thus, the correct reason is the formation of intermolecular hydrogen bonding.
Answer:Option D: Formation of intermolecular hydrogen bonding.