Question

Explain why carboxylic acids exist as associated molecules.

Hint:

Carboxylic acids form stable cyclic dimers due to double hydrogen bonding, especially in the vapour phase and non-polar solvents.

Answer 1

Step 1: Carboxylic acids contain both a \(-\text{OH}\) group and a carbonyl (\(>\text{C}=O\)) group.
Step 2: The hydrogen of the \(-\text{OH}\) group forms a strong hydrogen bond with the oxygen atom of the carbonyl group of another carboxylic acid molecule.
Step 3: Two molecules associate to form a cyclic dimer through two intermolecular hydrogen bonds.
Step 4: This dimeric association increases molecular mass and intermolecular attraction, causing higher boiling points of carboxylic acids.