Question

If you had a group of hydrocarbons, what structural features would you look at to rank the hydrocarbons in order of increasing boiling point?

Short answer

Carbon-carbon chain length and branching are some of the structural features that affects increase in boiling point.

Step-by-step solution

Strength of the intermolecular forces

The greater the intermolecular forces, the higher is the boiling point. We need to take into consideration all intermolecular forces (ionic, hydrogen bonding, dipole-dipole interaction, and London dispersion force). Size and shape are the two most important structural features relating to the strength of London dispersion forces. For size, the bigger the molecule (the larger the molar mass), the stronger the London dispersion forces and the higher the boiling point. For shape, the more branching present in a compound, the weaker the London dispersion forces and the lower the boiling point.

Length of the carbon-carbon chain

As the length of the carbon-carbon chain increases, the boiling point also increases.