A level Chemistry · Edexcel 9CH0 · Topic 6E
Alcohols
Key points
- Alcohols contain –OH; they are primary (one carbon attached to the C–OH carbon), secondary (two) or tertiary (three).
- They have high boiling points and short-chain ones mix with water because of hydrogen bonding.
- Combustion gives CO₂ and H₂O. With PCl₅ or with KBr/conc. H₂SO₄ they form halogenoalkanes (PCl₅ gives steamy HCl fumes — a test for –OH).
- Oxidation with acidified potassium dichromate(VI) (orange → green): primary → aldehyde (distil off) → carboxylic acid (heat under reflux); secondary → ketone; tertiary not oxidised.
- Dehydration with hot concentrated phosphoric acid gives an alkene.
- Practical skills: reflux stops volatile substances escaping; distillation separates by boiling point; use a separating funnel, drying agent (anhydrous MgSO₄) and redistillation to purify.
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Alcohols are among the most versatile organic compounds: they can be oxidised, dehydrated or turned into halogenoalkanes. This sub-topic also teaches the core lab techniques of organic synthesis, heating under reflux, distillation and…
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