Reaction routes and functional-group tests
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The teaching part (2 min) is free to watch. A free account opens the whole lecture: 1 worked example, 2 practice questions, 3 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Chemistry as a map
- The main interconversions
- More interconversions
- Planning a synthesis
Read the transcript of the teaching part
Last time
Before we start: last time, in Polymers and disposal, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Chemistry as a map
Organic chemistry looks like hundreds of unrelated reactions. But it is really one map: each functional group is a town, and each reaction a road between towns. A synthesis question asks you to plan a journey from one town to another, and a test question asks you to read the road signs.
The main interconversions
Alkane to halogenoalkane: chlorine or bromine with UV light, free-radical substitution. Alkene to halogenoalkane: HBr, room temperature. Alkene to alcohol: steam and phosphoric acid. Alkene to dihalide: bromine. Halogenoalkane to alcohol: NaOH(aq), warm. To alkene: NaOH in ethanol, heat. To nitrile: KCN in ethanol. To amine: excess NH three in ethanol. Alcohol to alkene: concentrated acid or Al two O three. To aldehyde, ketone or acid: acidified dichromate. To ester: carboxylic acid with acid catalyst.
More interconversions
Aldehyde or ketone to alcohol: NaBH four or LiAlH four. Aldehyde to acid: acidified dichromate. Carbonyl to hydroxynitrile: HCN with KCN. Carboxylic acid to alcohol: LiAlH four. To ester: alcohol with acid catalyst. Ester to acid or salt: hydrolysis. Nitrile to acid: dilute acid, reflux. Nitrile to amine: H two with Ni, or LiAlH four.
Planning a synthesis
Work backwards from the target. Ask: what functional group do I have, and what do I need? Count carbons. If the chain gets longer, a nitrile or a Grignard-type step is needed. Only the nitrile route is in this course. For each step, give the reagent, the solvent, the conditions, and the type of reaction.
Chapter 21: Analytical techniques and synthesis
- Reaction routes and functional-group tests 7 min
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