BRAINCAKEPlanning a Multi-Step Synthesis
When you are asked to plan a multi-step synthesis, a systematic approach helps.
1. Compare the functional groups in the starting material and the target.
2. Compare the number of carbon atoms. If the chain must get longer, you need a carbon-carbon bond forming step: KCN with a halogenoalkane, HCN with an aldehyde or ketone, or a Grignard reagent.
3. Work backwards from the target. Ask: what could this be made from in one step? Repeat until you reach something you can make from the starting material.
4. Give full reagents and conditions for every step, and name each intermediate.
5. Check the route: fewer steps give a higher overall yield; avoid very hazardous reagents where possible; consider whether a product will be a racemic mixture.
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All 11 lessons in Organic Synthesis · All Edexcel A-level Chemistry topics