Which of the following compounds has the highest boiling point due to hydrogen bonding?

Butanol has the highest boiling point among the given options primarily due to its ability to engage in hydrogen bonding. Hydrogen bonding occurs when a hydrogen atom is covalently bonded to a highly electronegative atom, such as oxygen, and is attracted to another electronegative atom nearby with a lone pair of electrons. In butanol, the hydroxyl group (-OH) allows it to form hydrogen bonds with other butanol molecules, significantly increasing the energy required to break these interactions during the phase change from liquid to gas.

In contrast, the other compounds listed—hexane, cyclohexane, and pentane—are hydrocarbons that lack hydroxyl groups. While they can experience London dispersion forces, which are present in all molecules, they do not have the strong intermolecular forces that hydrogen bonding provides. As a result, these compounds generally exhibit lower boiling points compared to alcohols like butanol, which benefit from stronger hydrogen bonds. Thus, butanol's hydrogen bonding capability is the key factor contributing to its higher boiling point.