The -OH (hydroxyl) functional group is responsible for the distinctive properties of alcohols that set them apart from alkanes.
- Solubility in water: The -OH group can form strong attractions with water molecules, allowing short-chain alcohols (methanol, ethanol) to mix completely with water. As chain length increases, solubility decreases because the hydrocarbon chain dominates the molecule's character.
- Higher boiling point than alkanes: The -OH group forms strong attractions between alcohol molecules. These attractions require extra energy to break, giving alcohols much higher boiling points than alkanes of similar size. Ethanol boils at 78°C; ethane boils at -89°C.
- Reactivity: The -OH group is a reactive functional group — it can be oxidised to a carboxylic acid, or replaced in substitution reactions.
This how it works covers How the -OH Group Determines Properties within Alcohols for GCSE Chemistry. Revise Alcohols in Organic Chemistry for GCSE Chemistry with 22 exam-style questions and 15 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 3 of 13 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Alcohols
What is the functional group present in all alcohols?
Explain what happens when ethanol reacts with sodium metal. Include a balanced equation in your answer.
Quick recall flashcards
What are alcohols?
Organic compounds containing the -OH hydroxyl functional group
What is hydration of ethene?
Adding water to ethene to produce ethanol: C₂H₄ + H₂O → C₂H₅OH