Organic Synthesis

Revise Organic Synthesis for Chemistry 9701 (AS Level) — revision notes and instant AI marking.

📖 Revision notes · preview

Cambridge International AS & A Level Chemistry (9701)

Organic Synthesis

The big idea: Synthesis questions test whether you can use every AS reaction as a tool: spot each functional group in a complicated molecule, predict what each reagent does to it, and chain reactions together into a route, naming the reagents, conditions, reaction types and by-products at every step.

Summary — What This Chapter Covers

Identify functional groups in a multi-functional molecule using the syllabus tests.
Predict properties and reactions group by group.
Devise multi-step routes using only syllabus reactions.
Analyse a given route: reaction type, reagents and possible by-products for each step.

1. Organic Synthesis

21.1

The AS reaction map

From	To	Reagents and conditions	Type
alkane	halogenoalkane	Cl₂ or Br₂, UV light	free-radical substitution
alkene	alkane	H₂, Pt/Ni, heat	addition (hydrogenation)
alkene	alcohol	H₂O(g), H₃PO₄	electrophilic addition
alkene	halogenoalkane	HX(g) or X₂, room temperature	electrophilic addition
alkene	diol	cold dilute acidified KMnO₄	oxidation
halogenoalkane	alcohol	NaOH(aq), heat	nucleophilic substitution
halogenoalkane	nitrile (+1 C)	KCN in ethanol, heat	nucleophilic substitution
halogenoalkane	amine	NH₃ in ethanol, heat, pressure	nucleophilic substitution
halogenoalkane	alkene	NaOH in ethanol, heat	elimination
alcohol	halogenoalkane	PCl₅, PCl₃/heat, SOCl₂, HX, or KCl + conc. H₂SO₄	substitution
alcohol	alkene	heated Al₂O₃ or conc. H₂SO₄	elimination (dehydration)
1° alcohol	aldehyde / carboxylic acid	acidified K₂Cr₂O₇, distil / reflux	oxidation
2° alcohol	ketone	acidified K₂Cr₂O₇, heat	oxidation
aldehyde / ketone	alcohol	NaBH₄ or LiAlH₄	reduction
aldehyde / ketone	hydroxynitrile (+1 C)	HCN, KCN catalyst, heat	nucleophilic addition
nitrile	carboxylic acid	dilute acid, or alkali then acid; reflux	hydrolysis
carboxylic acid	1° alcohol	LiAlH₄	reduction
carboxylic acid + alcohol	ester	conc. H₂SO₄, heat	condensation
ester	acid (or salt) + alcohol	dilute acid or alkali, heat	hydrolysis

Strategy for a route

Compare carbon counts. One more carbon means a CN step (KCN on a halogenoalkane, or HCN on a carbonyl).
Compare functional groups and their positions. Moving a group along the chain usually goes through an alkene (eliminate, then add back).
Work backwards from the target: what one step makes it, and from what?
For each step, give the reagent, the conditions, and the type of reaction.

21.1

Worked routes

Worked Example

Convert propan-1-ol into propan-2-ol.

Worked Example

Convert ethene into propanoic acid in three steps.

Worked Example

Compound Z is HOCH₂CH=CHCHO. Predict what Z does with (a) aqueous bromine, (b) 2,4-DNPH, (c) Tollens’ reagent, (d) NaBH₄, (e) excess acidified K₂Cr₂O₇ under reflux, (f) sodium.

Analysing a given route: by-products to watch for

Free-radical substitution gives a mixture: multiple substitution and termination products.
₂

Practice Question

Memorise

Add a carbon

KCN on RX, or HCN/KCN on C=O

🔓 Read the full Organic Synthesis note → You're seeing the preview · sign in to read it all

What's inside

📖 Revision notes 🎯 Learn mode ✦ AI flashcards ✓ Instant AI marking 🧊 3D explorers 🧪 Experiments & simulations 📈 Progress tracking

📄 Practise Organic Synthesis with Chemistry 9701 past papers Every paper with its mark scheme — answer online, marked instantly. Open →

Read the full Organic Synthesis notes free

That's the preview — create a free account to read the rest, plus flashcards and practice questions with instant AI marking. No credit card.

Unlock the full notes free →

Organic Synthesis