A LITTLE LIGHTBULB MOMENT
Alcohols, ethers, epoxides and sulfur chemistry
Small alcohols dissolve well; long chains resist water
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Short alcohols hug water; long hydrocarbon tails scare it off.
The idea behind the cue
Low-molecular-weight alcohols are quite water-soluble because the hydroxyl group hydrogen-bonds with water. As the hydrocarbon chain grows, the nonpolar portion dominates and solubility drops.
Practice this flashcard →Make it memorable
Short & simple
Short alcohols hug water; long hydrocarbon tails scare it off.
Acronym
SC — Sparkly Cupcakes.
Story
Methanol jumps straight into a glass of water like it belongs there. Octanol arrives wearing a huge oily coat, and the water crowd gives it a wide berth.
Connect the pieces
- S (Sparkly) → Solubility: Small alcohols dissolve well in water because the hydroxyl group hydrogen-bonds with water.
- C (Cupcakes) → Carbon-count: As the hydrocarbon chain gets longer, the nonpolar part dominates and water solubility drops overall.
- Sparkly · Solubility: Small alcohols dissolve well in water because the hydroxyl group hydrogen-bonds with water.
- Cupcakes · Carbon-count: As the hydrocarbon chain gets longer, the nonpolar part dominates and water solubility drops overall.
Know the limits
Branching can improve solubility somewhat, but increasing carbon count still reduces water solubility overall.
Further reading · OpenStax Organic Chemistry ↗Check your understanding
What generally happens to alcohol water solubility as the hydrocarbon chain gets longer?
A. It increases without limit
B. It stays exactly the same
C. It becomes impossible for any alcohol to dissolve
D. It decreases
Reveal explanation
It decreases
A larger nonpolar chain makes the molecule less compatible with water, so solubility decreases.