Compared to alcohols, why do carbonyl compounds generally have lower boiling points?

Carbonyl compounds generally have lower boiling points than alcohols primarily because they do not form hydrogen bonds. Alcohols possess a hydroxyl (-OH) group, which enables them to engage in hydrogen bonding with one another. This type of bonding significantly increases the boiling point of alcohols, as more energy is required to break these hydrogen bonds during the phase change from liquid to gas.

In contrast, carbonyl compounds (such as aldehydes and ketones) have a carbonyl group (C=O), which while polar, does not allow for the same kind of hydrogen bonding found in alcohols. Instead, the dipole-dipole interactions between carbonyl molecules are generally weaker than the hydrogen bonds present in alcohols. As a result, carbonyl compounds require less energy to boil, leading to their lower boiling points compared to alcohols.

While the other options do present certain characteristics of carbonyl compounds, they do not directly address the primary reason for the difference in boiling points. For instance, carbonyl compounds can be polar, they may be larger or smaller than alcohols depending on their structure, and while they contain oxygen, the presence of heavier atoms doesn’t inherently lower the boiling point. The key factor affecting boiling point in this context is