Which of the following statements is true regarding the physical properties of carboxylic acids?

Carboxylic acids are known to form dimers in solution due to the ability of their -COOH (carboxyl) groups to participate in hydrogen bonding. This interaction leads to the formation of a dimer, where two carboxylic acid molecules are held together through hydrogen bonds, effectively increasing the molecular size and influencing their physical properties, such as boiling points.

This dimerization is particularly significant in nonpolar solvents or at lower concentrations, where the intermolecular hydrogen bonding becomes the dominant factor affecting their behavior. Due to this ability to dimerize, carboxylic acids generally display higher boiling points compared to molecules that do not engage in such extensive hydrogen bonding.

In contrast, the other options present inaccuracies. Carboxylic acids typically have higher boiling points due to hydrogen bonding, are polar due to their functional groups, and obviously, they do contain functional groups, specifically the carboxyl group. Thus, the statement regarding dimers is correct as it highlights a unique characteristic of carboxylic acids and their interactions in solution.