Ethylene glycol (ethane-1,2-diol)

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• Ethylene glycol has two –OH groups, so it forms strong hydrogen bonding.
• It lowers the freezing point of water (freezing point depression).
• It also raises the boiling point, preventing overheating.

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✔ Used as antifreeze because it prevents water from freezing in cold conditions.

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Other than ethylene glycol, there are a few compounds used as antifreeze:

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Other Antifreeze Compounds

1. Propylene glycol (propane-1,2-diol)

• Less toxic than ethylene glycol
• Used in safer antifreeze formulations (food-grade systems)

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2. Glycerol (glycerine, propane-1,2,3-triol)

• Has three –OH groups → strong H-bonding
• Good freezing point depression
• Used in older or special applications

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3. Methanol / Ethanol

• Also lower freezing point
• But ❌ not preferred because:
  • Highly volatile
  • Flammable
  • Evaporate easily

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