Question

Which substance has the higher boiling point: CH3CH2CH3 or CH3CH2CH2CH2CH3? Explain.

Answer 1

Intermolecular forces are at work and determine boiling points.

In alkanes there are only carbon and hydrogen. The partial charge of the carbon of one molecule is only weakly attracted to the hydrogen partial charge of a neighbouring molecule. These weak intermolecular forces result in a low boiling point as they are easily broken.

Alcohol terminates on a OH group. The intermolecular forces between the partial charge of Oxygen and a hydrogen of a neighbouring molecule is significantly stronger, resulting in a significantly higher boiling point.