A LITTLE LIGHTBULB MOMENT
Alcohols, ethers, epoxides and sulfur chemistry
Alcohols boil high from intermolecular H-bonding
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Alcohols cling together like Velcro because of O-H hydrogen bonding.
The idea behind the cue
Alcohols have higher boiling points than similar-sized alkanes and ethers because the O-H group can both donate and accept hydrogen bonds. Stronger intermolecular attraction means more energy is required to separate molecules into vapor.
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Short & simple
Alcohols cling together like Velcro because of O-H hydrogen bonding.
Acronym
BH — Bouncy Hedgehogs.
Story
Three bottles sit on a hot plate: pentane skates away first, an ether follows, but ethanol keeps grabbing its neighbors by the hand. The crowd needs extra heat to pull the alcohol apart.
Connect the pieces
- B (Bouncy) → Boiling: Alcohols have higher boiling points than similar-sized alkanes and ethers because intermolecular attractions are stronger.
- H (Hedgehogs) → Hydrogen-bonding: The O-H group can both donate and accept hydrogen bonds, which raises the boiling point.
- Bouncy · Boiling: Alcohols have higher boiling points than similar-sized alkanes and ethers because intermolecular attractions are stronger.
- Hedgehogs · Hydrogen-bonding: The O-H group can both donate and accept hydrogen bonds, which raises the boiling point.
Know the limits
This comparison is most useful for molecules of similar size; very large molecules can have high boiling points for other reasons too.
Further reading · OpenStax Organic Chemistry ↗Check your understanding
Why do alcohols usually boil at higher temperatures than comparable alkanes and ethers?
A. They have weaker dispersion forces
B. They cannot rotate around C-C bonds
C. They form intermolecular hydrogen bonds
D. They are always ionic in liquid form
Reveal explanation
They form intermolecular hydrogen bonds
Alcohols can hydrogen bond through the O-H group, increasing intermolecular attraction and raising boiling point.