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.
⚙️ How the -OH Group Determines Properties
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.
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