BRAINCAKERedistillation and Purification
After washing and drying, an organic liquid is nearly pure but may still contain other organic compounds, such as unreacted starting material or side products. The final step is redistillation: the dried liquid is distilled again and only the fraction that boils at the product's boiling point is collected.
The dried liquid is heated in a clean, dry flask with anti-bumping granules in distillation apparatus, and the thermometer is watched closely. Liquid that distils below the product's boiling point is collected separately and discarded. When the temperature reaches the boiling point, a fresh, weighed collecting flask is used. Collection stops when the temperature rises above the range, leaving higher-boiling impurities in the flask. A narrow range, typically within about 2 °C of the boiling point, is collected.
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More in Organic Synthesis
- Heating under Reflux
- Distillation
- Using a Separating Funnel
- Drying an Organic Liquid
- Identifying Functional Groups
- Two-Stage Synthetic Routes
- Predicting Properties from Functional Groups
All 8 lessons in Organic Synthesis · All OCR AS-level Chemistry topics