Final answer:
Alcohols display higher boiling points than similar molar mass alkanes due to the presence of hydrogen bonding, which is a stronger intermolecular force than the London dispersion forces present in alkanes.
Step-by-step explanation:
Alcohols have high boiling points due to the effect of hydrogen bonding. This type of intermolecular force occurs between the hydrogen atom of one alcohol molecule and the oxygen atom of a neighboring alcohol molecule. The OH group in alcohols facilitates this hydrogen bonding, which is significantly stronger than the London dispersion forces found in alkanes. Since hydrogen bonds are stronger and require more thermal energy to break, alcohols need to be heated to a higher temperature to reach their boiling points compared to alkanes with similar molar masses.
For example, when comparing alkanes and alcohols of similar molar mass, alcohols show higher boiling points because it takes more energy to overcome both the hydrogen bonds and the London dispersion forces in alcohols, compared to just London dispersion forces in alkanes. This phenomenon also explains why alcohols with higher molar masses have correspondingly higher boiling points.