9701 Chemistry · Topics 21 & 35 · AS + A Level
Organic Synthesis Reagent Map — A Level Chemistry 9701 Cheat Sheet
Synthesis questions do not test new chemistry — they test whether you can find a route through everything you already know. This sheet is the complete reagent map: every functional group interconversion in the 9701 syllabus with its reagent and conditions, plus the strategy for planning a route, changing the carbon chain length, and spotting the conversions that need two steps.
✅ 14 worked sections
🎓 CAIE 9701 syllabus-mapped
⭐ 4.8 rated tutors
What’s on this cheat sheet
Organic Synthesis — Reagent Map
01 · How to plan a route
1 Count the carbons in start and target. Same number? Then no chain step is needed. One more? Go through a nitrile.
2 Identify the functional group change and pick the reagent from the map below.
3 Work backwards from the target when the forward route is not obvious, and always quote reagent and conditions for each step.
02 · From an alkene
| To | Reagent and conditions |
|---|---|
| alkane | H₂, Ni, 150 °C |
| halogenoalkane | HBr, room temp |
| dihalide | Br₂, room temp |
| alcohol | steam, H₃PO₄, 300 °C, 60 atm |
| diol | cold dilute acidified KMnO₄ |
| polymer | high pressure or catalyst |
03 · From a halogenoalkane
| To | Reagent and conditions |
|---|---|
| alcohol | NaOH(aq), warm |
| alkene | KOH in ethanol, hot |
| nitrile (+1 C) | KCN in ethanol, reflux |
| amine | excess NH₃ in ethanol, heat |
04 · From an alcohol
| To | Reagent and conditions |
|---|---|
| aldehyde | K₂Cr₂O₇ / H⁺, distil off |
| carboxylic acid | K₂Cr₂O₇ / H⁺, reflux |
| ketone (from 2°) | K₂Cr₂O₇ / H⁺, reflux |
| alkene | conc. H₂SO₄, 170 °C |
| halogenoalkane | PCl₅, or HCl / ZnCl₂ |
| ester | carboxylic acid, conc. H₂SO₄, reflux |
05 · From a carbonyl
| To | Reagent and conditions |
|---|---|
| alcohol | NaBH₄ or LiAlH₄ |
| carboxylic acid | K₂Cr₂O₇ / H⁺, reflux (aldehyde only) |
| hydroxynitrile (+1 C) | NaCN with dilute acid |
06 · From an acid or nitrile
| Change | Reagent and conditions |
|---|---|
| acid → alcohol | LiAlH₄ in dry ether |
| acid → acyl chloride | PCl₅ |
| acid → ester | alcohol, conc. H₂SO₄, reflux |
| nitrile → acid | dilute HCl, reflux |
| nitrile → amine | LiAlH₄, or H₂ / Ni |
07 · Aromatic routes A2
| Change | Reagent and conditions |
|---|---|
| benzene → nitrobenzene | conc. HNO₃ / conc. H₂SO₄, 55 °C |
| nitrobenzene → phenylamine | Sn / conc. HCl, then NaOH |
| benzene → alkylbenzene | RCl / AlCl₃ |
| methylbenzene → benzoic acid | hot alkaline KMnO₄, then H⁺ |
08 · Changing the chain length
Add one carbon: halogenoalkane + KCN, or carbonyl + HCN. Both give a nitrile group that can then become –COOH or –CH₂NH₂.
Shorten a chain: vigorous oxidation of an alkene, or oxidation of an alkyl side chain on a ring. These are the only routes the syllabus expects.
09 · Worked example — alkene to ketone
Same carbon count, so no nitrile is needed.
1 · HBr, room temperature → 2‑bromopropane
2 · NaOH(aq), warm → propan‑2‑ol
3 · K₂Cr₂O₇ / H⁺, reflux → propanone
Markovnikov puts the group on carbon 2, so the alcohol is secondary and the product is a ketone. Propanoic acid cannot be made from propene at this level — start from propan‑1‑ol instead.
10 · Worked example — chain lengthening
Three carbons from two, so a nitrile step is required.
1 · PCl₅ (or HCl / ZnCl₂) → chloroethane
2 · KCN in ethanol, reflux → propanenitrile
3 · dilute HCl, reflux → propanoic acid
11 · Purification and yield
Liquids: distillation for a volatile product, or a separating funnel followed by drying with anhydrous CaCl₂ or MgSO₄.
Solids: recrystallise from a suitable solvent, filter under reduced pressure, dry, then check purity by melting point — a sharp value at the literature figure means pure.
12 · Tests that identify a group
| Group | Test and result |
|---|---|
| C=C | Br₂(aq) decolourised |
| –OH | PCl₅ → steamy HCl fumes |
| C=O | 2,4‑DNPH → orange ppt |
| –CHO | Tollens’ → silver mirror |
| –COOH | Na₂CO₃ → fizzing |
| CH₃CO– or CH₃CH(OH)– | I₂ / NaOH → yellow ppt |
| halogenoalkane | NaOH then HNO₃ and AgNO₃ → ppt |
13 · Worked example — three steps
Four carbons from three → one nitrile step.
1 · PCl₅ → 1‑chloropropane
2 · KCN in ethanol, reflux → butanenitrile
3 · LiAlH₄ in dry ether → 1‑aminobutane
Reacting the chloropropane with ammonia instead would give propylamine — one carbon short.
Marks lost here
— Giving a reagent without its conditions, or the wrong solvent for substitution against elimination.
— Ignoring the carbon count and proposing a route that cannot change it.
— Choosing an order that puts a directing group on the ring too early.
— Using reflux where the product must be distilled off, so the aldehyde is over‑oxidised.
Get all 25 topic cheat sheets for 9701 Chemistry
One free PDF pack, AS + A Level, straight to WhatsApp.
Organic Synthesis Reagent Map — A Level Chemistry 9701 — Frequently Asked Questions
How do you lengthen a carbon chain in 9701?
Two routes. Add HCN to an aldehyde or ketone to make a hydroxynitrile, or react a halogenoalkane with ethanolic potassium cyanide to make a nitrile. Both add one carbon; the nitrile can then be hydrolysed to a carboxylic acid or reduced to a primary amine.
How should you plan a multi-step synthesis?
Work backwards from the target. Identify its functional group and ask what single reaction could have made it, then repeat until you reach the starting material. Check at each step whether the carbon skeleton has changed — that is usually the constraint that decides the route.
Which conversions cannot be done in one step?
An alkane to an alcohol, a benzene ring to phenylamine, and a ketone to a carboxylic acid all need two or more steps. Recognising these quickly saves time in an exam.
