Which compound would you expect to have the highest boiling point?

The compound with the highest boiling point among the choices provided is indeed hexanoic acid. The boiling point of a compound is influenced by various intermolecular forces, and hexanoic acid exhibits strong intermolecular hydrogen bonding due to the presence of a carboxylic acid functional group.

The carboxylic acid group (-COOH) allows hexanoic acid to form hydrogen bonds with itself, which significantly raises its boiling point compared to compounds that do not have this capability. In contrast, while ethanol also has the capacity to form hydrogen bonds due to its hydroxyl group (-OH), the presence of the carboxylic acid group in hexanoic acid leads to more extensive hydrogen bonding interactions.

Hexane and butanol, although they have different intermolecular forces, are primarily affected by Van der Waals forces (in the case of hexane, which is nonpolar) and hydrogen bonding (in butanol, which has only one -OH group). However, neither has the same degree of hydrogen bonding capability as hexanoic acid.

Therefore, due to the presence of the carboxylic acid functional group and the resulting stronger hydrogen bonding, hexanoic acid exhibits the highest boiling point among the options presented.