📐 Edexcel A-Level Chemistry
Organic Synthesis
Mastery Kit
A complete, science-of-learning-powered resource to achieve A* on organic synthesis — reactions, mechanisms, analysis, flashcards, and exam practice.
Topics 6 · 17 · 18
AS + A2 Content
90%+ Target
Spaced Retrieval
Science of Learning: Your Route to A*
Research-backed techniques shown to 2–4× learning efficiency. Apply these to every section of this kit.
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1 — Spaced Retrieval Practice
Don’t re-read notes. Instead, close them and try to recall. The effort of reconstruction strengthens long-term memory and prevents cramming. Revisit each reaction set after 1 day, then 3 days, then 1 week.
→ Use the Flashcard tab: do 10 cards, wait 24h, repeat. Mark difficult cards and return to them twice as often.
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2 — Interleaved Practice
Never drill one reaction type 30 times in a row. Mix alkenes + haloalkanes + carbonyl questions in a single session. Research shows interleaving can triple average exam performance on reaction selection tasks.
→ In the Practice Qs tab, work through them in mixed order — don’t group by type.
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3 — Dual Coding
Pair verbal information with visuals. Every reaction should exist in your memory as both words AND a structural diagram. The Pathway Map tab combines both simultaneously.
→ For each reaction, draw the structural formula from scratch (free recall) before checking your notes.
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4 — Elaborative Interrogation
Ask “WHY?” for every reagent and condition. Why NaBH₄ not LiAlH₄ for a carbonyl? Why reflux for esterification? Understanding the mechanism prevents confusion under pressure.
→ Before memorising a reagent, explain its role to yourself or a peer. If you can’t, you don’t know it yet.
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5 — Chunking by Functional Group
Group all ~50 reactions into 9 functional group “chunks”. Master one chunk fully before adding another — but then interleave them. This builds a flexible schema for designing multi-step routes.
→ Follow the study planner — it sequences chunks optimally then enforces interleaving from Week 5.
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6 — Free Recall Sheets
Every 2–3 days, take a blank sheet and write every reaction you know from memory: starting material → reagents/conditions → product → mechanism type. Then compare to the Reactions tab and correct errors immediately.
→ This 20-minute exercise beats 2 hours of passive re-reading. Errors must be corrected same day.
The A* Formula: What the Exam Actually Needs
Based on Edexcel mark schemes, A* students must do all of these reliably:
✓ REAGENTS & CONDITIONS
Give the exact reagent (not a general one) AND the exact conditions (temperature, catalyst, solvent). Both must be correct for the mark.
✓ MECHANISMS
Curly arrows from bond/lone pair (not an atom). Correct intermediates. Correct partial charges (δ+ δ−). Correct products shown.
✓ MULTI-STEP SYNTHESIS
Plan backwards from target. Match C-chain length. Identify functional group changes. Give reagents for EACH step. Typically 2–4 steps.
✓ ANALYSIS
Link IR, MS, and chemical test observations precisely to functional groups. Distinguish aldehyde vs ketone, primary vs secondary alcohol, etc.
⚠️ COMMON STUDENT ERRORS — Verified From Edexcel Mark Schemes
❌ Writing “heat” without specifying temperature, reflux, or distillation
❌ Confusing NaBH₄ (mild — reduces C=O only) with LiAlH₄ (stronger — also reduces nitriles, esters, carboxylic acids)
❌ For ester hydrolysis: forgetting to specify acid conditions OR base conditions — not just “water and heat”
❌ Forgetting “anhydrous” for Friedel-Crafts — AlCl₃ catalyst is destroyed by water
❌ Drawing curly arrows starting from atom labels — must start from a bond or lone pair
❌ Benzene prefers electrophilic substitution NOT addition (addition would break delocalisation)
❌ Writing KMnO₄ instead of acidified K₂Cr₂O₇ for alcohol/aldehyde oxidation — these are different oxidising agents with different standard uses in Edexcel
❌ Labelling amine from halogenoalkane as AS content — this is A2 (Topic 17/18)
❌ For cyanohydrin: writing “add HCN” without noting CN⁻ is the actual nucleophile (HCN used in situ from KCN + H⁺)
❌ Attempting to oxidise a ketone to a carboxylic acid — ketones resist normal oxidation. Only aldehydes are oxidised to carboxylic acids
Complete Reaction Reference
All Edexcel A-level Chemistry (9CH0) specification reactions for Topics 6, 17 & 18. AS = AS / Year 1 content (Topics 6–7) · A2 = A2 / Year 2 only (Topics 17–18). ⚠️ Grignard reagents appear in Edexcel International A-level (IAL) only, not the UK 9CH0 spec.
⬡ ALKANES — Topic 6
| Starting Material | Product | Reagents | Conditions | Mechanism | Level |
|---|---|---|---|---|---|
| Alkane (C–H bond) | Haloalkane (mixture of products) | Cl₂ or Br₂ | UV light (ultraviolet, photochemical initiation) ⚠️ Limitation: mixture of mono/di/tri-substituted products formed — poor selectivity |
Free Radical Substitution (FRS): initiation → propagation → termination | AS |
| Long-chain alkane | Shorter alkane + alkene (+ H₂) | Thermal: heat only · Catalytic: silica/alumina (zeolite) catalyst | Thermal: very high temperature (~600–700°C), high pressure · Catalytic: ~600°C, zeolite, lower pressure | Cracking (thermal or catalytic) | AS |
⬡ ALKENES — Topic 6
| Starting Material | Product | Reagents | Conditions | Mechanism | Level |
|---|---|---|---|---|---|
| Alkene | Alkane (hydrogenation) | H₂ | Ni catalyst, ~150°C (or Pd/Pt at room temp) | Addition / Reduction | AS |
| Alkene | Dihalogenoalkane | Br₂ (in organic solvent e.g. hexane) or Cl₂ | Room temperature, no UV light needed Also used as test: orange bromine water → colourless | Electrophilic Addition | AS |
| Alkene | Halogenoalkane (mono) | HBr or HCl | Room temperature, pure gas or solution | Electrophilic Addition (Markovnikov’s rule applies to unsymmetrical alkenes) | AS |
| Alkene | Alcohol | Steam (H₂O) | H₃PO₄ catalyst (phosphoric acid), 300°C, 60–65 atm Industrial production of ethanol from ethene | Electrophilic Addition (hydration) | AS |
| Alkene | Diol (1,2-diol) | Cold dilute acidified KMnO₄ (potassium manganate(VII)) | Cold, dilute — purple KMnO₄ decolourises | Oxidation (addition of two OH groups across C=C) | A2 |
| Alkene monomers | Addition polymer | Initiator (e.g. organic peroxide) | High pressure, catalyst — conditions vary by monomer | Addition polymerisation (radical mechanism) | AS |
⬡ HALOGENOALKANES — Topics 6 & 17
| Starting Material | Product | Reagents | Conditions | Mechanism | Level |
|---|---|---|---|---|---|
| Halogenoalkane | Alcohol | NaOH (aqueous) | Heat under reflux (aqueous solvent favours substitution) | Nucleophilic Substitution (SN1 or SN2 depending on substrate) | AS |
| Halogenoalkane | Alkene | KOH dissolved in ethanol (ethanolic KOH) | Heat under reflux (ethanolic solvent favours elimination) ⚠️ Solvent is critical: aqueous → substitution; ethanolic → elimination | Elimination (E2) | AS |
| Halogenoalkane + excess NH₃ | Primary amine | Excess ethanolic ammonia (NH₃) | Sealed tube or pressure vessel, heat ⚠️ Excess NH₃ needed to minimise further substitution to 2°/3° amines | Nucleophilic Substitution | A2 |
| Halogenoalkane | Nitrile (+1 carbon) | KCN in ethanol (ethanolic KCN) | Heat under reflux Carbon chain extended by 1 — key in synthesis routes | Nucleophilic Substitution (CN⁻ is the nucleophile) | A2 |
⬡ ALCOHOLS — Topics 6 & 17
| Starting Material | Product | Reagents | Conditions | Mechanism | Level |
|---|---|---|---|---|---|
| Primary alcohol (1°) | Aldehyde | Acidified K₂Cr₂O₇ (K₂Cr₂O₇ + dilute H₂SO₄), shown as [O] | Warm gently + distil product immediately to prevent further oxidation Orange → green colour change observed | Oxidation | AS |
| Primary alcohol (1°) | Carboxylic acid | Acidified K₂Cr₂O₇ (excess [O]) | Heat under reflux (excess oxidising agent, product not removed) | Oxidation | AS |
| Secondary alcohol (2°) | Ketone | Acidified K₂Cr₂O₇ (represented as [O]) | Heat under reflux or warm Ketone cannot be oxidised further under normal conditions | Oxidation | AS |
| Tertiary alcohol (3°) | No reaction | Any oxidising agent | — | Resistant to oxidation (no H on C bearing OH) | AS |
| Alcohol | Alkene | Conc. H₃PO₄ (preferred) or conc. H₂SO₄ | Heat under reflux, ~170°C (H₂SO₄) or ~170–180°C (H₃PO₄) | Elimination / Dehydration (E1) | AS |
| Alcohol | Chloroalkane | PCl₅ (phosphorus pentachloride) | Room temperature (vigorous — HCl gas evolved and POCl₃ also formed) | Nucleophilic Substitution | AS |
| Alcohol | Bromoalkane | NaBr + conc. H₂SO₄ (or HBr gas) | Heat under reflux | Nucleophilic Substitution | AS |
| Alcohol | Ester | Carboxylic acid + conc. H₂SO₄ (catalyst) | Heat under reflux (reversible equilibrium) | Condensation / Esterification (reversible) | AS |
⬡ CARBONYLS: ALDEHYDES & KETONES — Topic 17
| Starting Material | Product | Reagents | Conditions | Mechanism | Level |
|---|---|---|---|---|---|
| Aldehyde → primary alcohol · Ketone → secondary alcohol | Alcohol | NaBH₄ (sodium tetrahydridoborate / sodium borohydride) | Aqueous ethanol (protic solvent), room temperature | Nucleophilic Addition / Reduction (H⁻ nucleophile from NaBH₄) | A2 |
| Aldehyde / Ketone | Hydroxynitrile (cyanohydrin) | HCN (produced in situ from KCN/NaCN + dilute H₂SO₄) — CN⁻ is the nucleophile | Room temperature, slightly acidic or neutral conditions Chain extended by +1 carbon; product has chiral centre → racemic mixture | Nucleophilic Addition (CN⁻ attacks carbonyl carbon) | A2 |
| Aldehyde (only) | Carboxylic acid | Acidified K₂Cr₂O₇ [O] | Heat under reflux ⚠️ Ketones do NOT oxidise further under normal conditions — this is an aldehyde-only reaction | Oxidation | A2 |
| Aldehyde / Ketone | Yellow/orange 2,4-DNP precipitate | 2,4-dinitrophenylhydrazine solution (Brady’s reagent / 2,4-DNPH) | Room temperature — yellow, orange or red-orange precipitate forms Confirms C=O present; does NOT distinguish aldehyde from ketone | Condensation (nucleophilic addition then elimination of water) | A2 |
| Aldehyde only (NOT ketones) | Tollens’: silver mirror · Fehling’s: brick-red Cu₂O precipitate | Tollens’ reagent (ammoniacal silver nitrate, [Ag(NH₃)₂]⁺) · OR Fehling’s solution (blue Cu²⁺ complex) | Warm gently in water bath Distinguishes aldehyde (positive) from ketone (no reaction) | Oxidation (aldehyde oxidised to carboxylate; Ag⁺ or Cu²⁺ reduced) | A2 |
⬡ CARBOXYLIC ACIDS & DERIVATIVES — Topics 17
| Starting Material | Product | Reagents | Conditions | Mechanism | Level |
|---|---|---|---|---|---|
| Carboxylic acid + alcohol | Ester + water | Conc. H₂SO₄ (catalyst) | Heat under reflux (reversible — equilibrium mixture) | Condensation / Esterification | AS |
| Carboxylic acid | Acyl chloride | PCl₅ (phosphorus pentachloride) or SOCl₂ (thionyl chloride) | Room temperature (vigorous, HCl gas evolved) | Nucleophilic Acyl Substitution | A2 |
| Ester | Carboxylic acid + alcohol | Dilute H₂SO₄ (acid hydrolysis) OR NaOH(aq) (base hydrolysis / saponification) | Heat under reflux · Base hydrolysis is irreversible and goes to completion | Hydrolysis | A2 |
| Acyl chloride + alcohol | Ester + HCl | Alcohol | Room temperature (faster than esterification — goes to completion, no catalyst needed) | Nucleophilic Acyl Substitution | A2 |
| Acyl chloride + NH₃ | Primary amide + HCl | Ammonia (NH₃) | Room temperature (very vigorous — white fumes of NH₄Cl also form) | Nucleophilic Acyl Substitution | A2 |
| Acyl chloride + amine (RNH₂) | Secondary amide + HCl | Primary or secondary amine | Room temperature | Nucleophilic Acyl Substitution | A2 |
⬡ AMINES — Topic 18
| Starting Material | Product | Reagents | Conditions | Mechanism | Level |
|---|---|---|---|---|---|
| Halogenoalkane + excess NH₃ | Primary amine (mainly) | Excess ethanolic ammonia | Sealed tube, heat under pressure ⚠️ Excess NH₃ minimises over-alkylation to 2° and 3° amines, but mixture still forms | Nucleophilic Substitution | A2 |
| Nitrile (R–CN) | Primary amine (R–CH₂NH₂) | LiAlH₄ in dry ether (anhydrous) OR H₂ + Ni catalyst | LiAlH₄: dry ether, then careful aqueous workup · H₂/Ni: high temp and pressure | Reduction | A2 |
| Nitrobenzene | Phenylamine (aniline) | Sn (tin) + conc. HCl | Heat under reflux; then add NaOH to liberate free amine from its salt | Reduction | A2 |
| Amine + acyl chloride | Amide (N-substituted) | Acyl chloride (RCOCl) | Room temperature (vigorous) | Nucleophilic Acyl Substitution | A2 |
⬡ ARENES (BENZENE & DERIVATIVES) — Topic 18 (A2 Only)
| Starting Material | Product | Reagents | Conditions | Mechanism | Level |
|---|---|---|---|---|---|
| Benzene | Nitrobenzene | Conc. HNO₃ + conc. H₂SO₄ (catalyst) | 50°C — do not exceed 55°C to prevent di-nitration Electrophile formed: HNO₃ + 2H₂SO₄ → NO₂⁺ + 2HSO₄⁻ + H₃O⁺ | Electrophilic Substitution (electrophile: NO₂⁺) | A2 |
| Benzene | Halobenzene (e.g. bromobenzene) | Br₂ + FeBr₃ (Lewis acid halogen carrier) · or AlBr₃; use AlCl₃/FeCl₃ for chlorination | Room temperature, anhydrous FeBr₃ is the catalyst — can be made in situ from Fe + Br₂ | Electrophilic Substitution | A2 |
| Benzene | Alkylbenzene | Chloroalkane (RCl) + anhydrous AlCl₃ (Lewis acid catalyst) | Anhydrous, heat under reflux ⚠️ Over-alkylation is a limitation — product is more reactive than benzene | Friedel-Crafts Alkylation (electrophilic substitution; electrophile: R⁺) | A2 |
| Benzene | Aryl ketone (e.g. phenylethanone) | Acyl chloride (RCOCl) + anhydrous AlCl₃ | Anhydrous, heat under reflux (~50°C) Preferred over alkylation: C=O deactivates ring, preventing over-acylation | Friedel-Crafts Acylation (electrophilic substitution; electrophile: RCO⁺) | A2 |
| Benzene | Cyclohexane | H₂ | Ni catalyst, 200°C, 30 atm pressure | Addition / Reduction (ring loses aromaticity) | A2 |
⚠️ IMPORTANT: Grignard Reagents (RMgX) — Edexcel UK (9CH0) vs International A-level (IAL)
Grignard reagents are NOT in the Edexcel UK A-level (9CH0) specification. They appear in the Edexcel International Advanced Level (IAL) — Units 4/5. If you are studying the standard UK A-level (9CH0), you do not need Grignard reactions. If studying IAL, the reactions are: RMgX + methanal → 1° alcohol (+1C); + aldehyde → 2° alcohol; + ketone → 3° alcohol; + CO₂ → carboxylic acid. All require anhydrous ether conditions.
Organic Synthesis Pathway Map
The complete interconversion web — use this to plan multi-step synthesis routes. Master this map by covering it and drawing it from scratch.
FUNCTIONAL GROUP INTERCONVERSION MASTER MAP — Edexcel A-Level
🗺️ HOW TO USE THIS MAP FOR SYNTHESIS QUESTIONS
Step 1: Identify the starting material functional group and the target functional group.
Step 2: Trace a pathway between them — if no direct arrow exists, find a 2–3 step route.
Step 3: Check C-chain length at each step — use nitrile formation to add +1C.
Step 4: Write out each step with exact reagents, conditions, and reaction type.
Step 2: Trace a pathway between them — if no direct arrow exists, find a 2–3 step route.
Step 3: Check C-chain length at each step — use nitrile formation to add +1C.
Step 4: Write out each step with exact reagents, conditions, and reaction type.
Spaced Retrieval Flashcards
Click any card to reveal the answer. Use these in a randomised order — never grouped by type. Re-test on cards you struggled with 24 hours later.
Practice Questions
Mixed-type questions covering AS & A2 organic synthesis. Work through in the order shown (interleaved). Reveal the mark-scheme answer only after attempting.
Q1 — Alkenes & Mechanisms (AS)
4 marks
But-1-ene reacts with hydrogen bromide. (a) State the type of mechanism. (b) Identify the major organic product and explain why it is the major product using Markovnikov’s rule. (c) Give the reagents and conditions for the reverse reaction (product → but-1-ene).
(a) Electrophilic addition [1]
(b) Major product: 2-bromobutane [1]. Markovnikov’s rule: the electrophile (H⁺) adds to the carbon of the double bond with MORE hydrogens; the intermediate 2° carbocation is more stable than the 1° carbocation, so the Br⁻ adds to C-2. [1]
(c) KOH dissolved in ethanol (ethanolic KOH), heat under reflux [1]
(b) Major product: 2-bromobutane [1]. Markovnikov’s rule: the electrophile (H⁺) adds to the carbon of the double bond with MORE hydrogens; the intermediate 2° carbocation is more stable than the 1° carbocation, so the Br⁻ adds to C-2. [1]
(c) KOH dissolved in ethanol (ethanolic KOH), heat under reflux [1]
Q2 — Synthesis Route (AS/A2)
6 marks
Describe how you would convert propan-1-ol into propanoic acid in two different ways. For each, give reagents, conditions, and any intermediate compound formed.
Route 1 (direct oxidation):
Propan-1-ol → propanal (intermediate): acidified K₂Cr₂O₇, warm and distil immediately [1+1]
Propanal → propanoic acid: acidified K₂Cr₂O₇ (excess [O]), heat under reflux [1+1]
Route 2 (via haloalkane → nitrile → acid):
Propan-1-ol → 1-bromopropane: conc. HBr + H₂SO₄ or PCl₅, warm [1]
1-bromopropane → butanenitrile: ethanolic KCN, heat under reflux [1] → then acid hydrolysis to butanoic acid (note: +1C chain!)
Accept: direct from propan-1-ol → propanoic acid using acidified K₂Cr₂O₇ excess, reflux (1-step oxidation) for full credit if conditions clear.
Propan-1-ol → propanal (intermediate): acidified K₂Cr₂O₇, warm and distil immediately [1+1]
Propanal → propanoic acid: acidified K₂Cr₂O₇ (excess [O]), heat under reflux [1+1]
Route 2 (via haloalkane → nitrile → acid):
Propan-1-ol → 1-bromopropane: conc. HBr + H₂SO₄ or PCl₅, warm [1]
1-bromopropane → butanenitrile: ethanolic KCN, heat under reflux [1] → then acid hydrolysis to butanoic acid (note: +1C chain!)
Accept: direct from propan-1-ol → propanoic acid using acidified K₂Cr₂O₇ excess, reflux (1-step oxidation) for full credit if conditions clear.
Q3 — Carbonyl Compounds (A2)
5 marks
A student has two unlabelled bottles, one containing propanal and one containing propanone. Describe two chemical tests that would distinguish between them, giving expected observations for each compound in each test.
Test 1 — Tollens’ reagent (silver mirror test):
Add Tollens’ reagent (ammoniacal silver nitrate) and warm gently in a water bath.
Propanal: silver mirror formed on inside of test tube [1]
Propanone: no change / no silver mirror [1]
Test 2 — Fehling’s solution:
Add Fehling’s solution and heat.
Propanal: brick-red/orange precipitate of Cu₂O forms [1]
Propanone: solution remains blue [1]
Note: 2,4-DNP (Brady’s reagent) gives orange precipitate with BOTH — does NOT distinguish them. [1 for correctly stating this]
Add Tollens’ reagent (ammoniacal silver nitrate) and warm gently in a water bath.
Propanal: silver mirror formed on inside of test tube [1]
Propanone: no change / no silver mirror [1]
Test 2 — Fehling’s solution:
Add Fehling’s solution and heat.
Propanal: brick-red/orange precipitate of Cu₂O forms [1]
Propanone: solution remains blue [1]
Note: 2,4-DNP (Brady’s reagent) gives orange precipitate with BOTH — does NOT distinguish them. [1 for correctly stating this]
Q4 — Benzene Chemistry (A2)
5 marks
Benzene undergoes nitration. (a) Give the reagents and conditions. (b) Write the equation for the formation of the electrophile. (c) Outline the mechanism for the first step of the reaction (formation and attack of electrophile) using curly arrows.
(a) Concentrated HNO₃ and concentrated H₂SO₄ (catalyst); temperature kept below 55°C (at 50°C) [1+1]
(b) HNO₃ + 2H₂SO₄ → NO₂⁺ + 2HSO₄⁻ + H₃O⁺ [1]
(H₂SO₄ protonates HNO₃; loss of water generates nitronium ion NO₂⁺)
(c) Curly arrow from π-bond (C=C ring) to NO₂⁺ electrophile [1]; intermediate shows + charge on ring (arenium ion) [1]; curly arrow from C-H bond to restore aromaticity, releasing H⁺ [implied in description]
(b) HNO₃ + 2H₂SO₄ → NO₂⁺ + 2HSO₄⁻ + H₃O⁺ [1]
(H₂SO₄ protonates HNO₃; loss of water generates nitronium ion NO₂⁺)
(c) Curly arrow from π-bond (C=C ring) to NO₂⁺ electrophile [1]; intermediate shows + charge on ring (arenium ion) [1]; curly arrow from C-H bond to restore aromaticity, releasing H⁺ [implied in description]
Q5 — Multi-Step Synthesis (A2)
8 marks
Starting from ethanol (CH₃CH₂OH), outline the synthesis of butanenitrile (CH₃CH₂CH₂CN). Your answer must include all reagents, conditions, and equations for each step. State the type of reaction at each step.
Step 1: Ethanol → bromoethane
Reagents: Conc. H₂SO₄ + NaBr (or PBr₃); Conditions: warm [1+1]
Type: Nucleophilic Substitution [1]
Step 2: Bromoethane → propanenitrile (CH₃CH₂CN)
Reagents: Ethanolic KCN; Conditions: heat under reflux [1+1]
Type: Nucleophilic Substitution (+1 carbon) [1]
Step 3: Propanenitrile → butanenitrile (+1C again)
Note: To get butanenitrile (4C) from ethanol (2C) requires adding 2 carbons.
Alternative: Use 1-bromopropane as starting material from propan-1-ol, then KCN. [1]
Or: Apply KCN to bromoethane → propanenitrile, then reduce to propylamine — but butanenitrile requires one more C. Full credit for showing correct 3-step route with correct C-counting. [1]
Reagents: Conc. H₂SO₄ + NaBr (or PBr₃); Conditions: warm [1+1]
Type: Nucleophilic Substitution [1]
Step 2: Bromoethane → propanenitrile (CH₃CH₂CN)
Reagents: Ethanolic KCN; Conditions: heat under reflux [1+1]
Type: Nucleophilic Substitution (+1 carbon) [1]
Step 3: Propanenitrile → butanenitrile (+1C again)
Note: To get butanenitrile (4C) from ethanol (2C) requires adding 2 carbons.
Alternative: Use 1-bromopropane as starting material from propan-1-ol, then KCN. [1]
Or: Apply KCN to bromoethane → propanenitrile, then reduce to propylamine — but butanenitrile requires one more C. Full credit for showing correct 3-step route with correct C-counting. [1]
Q6 — Grignard Reagents (A2)
4 marks
A Grignard reagent, CH₃MgBr, reacts with propanal (CH₃CH₂CHO). (a) Give the type of reaction. (b) Name the product after aqueous acid workup. (c) State why anhydrous conditions are essential.
(a) Nucleophilic addition [1]
(b) Butan-2-ol (CH₃CH₂CH(OH)CH₃) — a secondary alcohol [1]
(Grignard adds methyl to C of CHO; acid workup protonates alkoxide; chain = 4C total)
(c) Grignard reagents react vigorously with water/protic solvents — even traces of water destroy the reagent by protonating the carbanion (RMgX + H₂O → RH + Mg(OH)X) [1+1]
(b) Butan-2-ol (CH₃CH₂CH(OH)CH₃) — a secondary alcohol [1]
(Grignard adds methyl to C of CHO; acid workup protonates alkoxide; chain = 4C total)
(c) Grignard reagents react vigorously with water/protic solvents — even traces of water destroy the reagent by protonating the carbanion (RMgX + H₂O → RH + Mg(OH)X) [1+1]
Exam-Style Questions
These mirror actual Edexcel Paper 2 & Paper 3 question styles. Attempt under timed conditions (1.2 min/mark). Reveal answers after attempting.
⬛ AS PAPER 2 STYLE — Topic 6
Question 1: Organic Reactions of Haloalkanes [10 marks]
2-chloropropane can undergo both substitution and elimination reactions with sodium hydroxide.
(a) State the reagents and conditions needed to favour elimination over substitution. Explain why these conditions favour elimination. [3]
(b) Name the organic product of the elimination reaction. [1]
(c) Draw the mechanism for the substitution reaction of 2-chloropropane with aqueous NaOH. Show all curly arrows and relevant partial charges. [4]
(d) Explain the relative rates of hydrolysis of 1-chlorobutane, 1-bromobutane, and 1-iodobutane with AgNO₃(aq). [2]
(a) Ethanolic (alcoholic) KOH; concentrated; heat under reflux [1 each, max 3]. Higher temperature favours breaking the stronger C–H bond; ethanolic solvent generates ethoxide (stronger base); concentrated base promotes the less common elimination pathway. [1 for any valid reason]
(b) Propene [1]
(c) Nucleophilic Substitution (SN2 or SN1):
• δ+ shown on C–Cl carbon [1]
• Curly arrow from lone pair on O of OH⁻ to C [1]
• Curly arrow from C–Cl bond to Cl [1]
• Products: propan-2-ol + Cl⁻ [1]
(d) Rate: iodo > bromo > chloro. The C–I bond has the lowest bond enthalpy so is easiest to break heterolytically in the rate-determining step. The C–Cl bond is strongest so hydrolyses slowest. [1+1]
(b) Propene [1]
(c) Nucleophilic Substitution (SN2 or SN1):
• δ+ shown on C–Cl carbon [1]
• Curly arrow from lone pair on O of OH⁻ to C [1]
• Curly arrow from C–Cl bond to Cl [1]
• Products: propan-2-ol + Cl⁻ [1]
(d) Rate: iodo > bromo > chloro. The C–I bond has the lowest bond enthalpy so is easiest to break heterolytically in the rate-determining step. The C–Cl bond is strongest so hydrolyses slowest. [1+1]
◆ A2 PAPER 2 STYLE — Topic 17 & 18
Question 2: Carbonyl Chemistry & Identification [12 marks]
An unknown compound X has molecular formula C₄H₈O. It decolourises acidified potassium manganate(VII), gives an orange precipitate with 2,4-DNP, but gives no silver mirror with Tollens’ reagent.
(a) Use the observations above to identify the functional group(s) present in X. [3]
(b) Give the name of compound X and draw its displayed formula. [2]
(c) Compound X reacts with NaBH₄. Give the type of reaction and name the organic product. [2]
(d) Describe a two-step synthesis to convert X into a carboxylic acid of the same carbon chain length. Give reagents, conditions, and intermediate. [3]
(e) What additional information from IR spectroscopy would confirm the functional group in X? [2]
(a) 2,4-DNP → carbonyl group (C=O) present [1]; No Tollens’ → not an aldehyde, must be a ketone [1]; Decolourises KMnO₄ → could indicate C=C, but since it’s a ketone (C₄H₈O), this may indicate oxidation of ketone under forcing conditions or presence of enol tautomer — alternatively accept: “the purple colour being lost indicates a reducing species or C=C” [1]
(b) Butanone (methyl ethyl ketone); CH₃COCH₂CH₃ [1+1]
(c) Nucleophilic addition / reduction [1]; Butan-2-ol [1]
(d) Step 1: Butanone → butan-2-ol (NaBH₄, aq. ethanol) [1]
Step 2: Butan-2-ol → butanone → (only ketone, can’t oxidise further to acid easily from here; instead note: to make butanoic acid from a ketone requires a different route)
Better answer: Oxidise using acidified K₂Cr₂O₇ under vigorous conditions — ketones resist further oxidation, so you cannot make butanoic acid directly from butanone in one step [1 for recognising this complication]; alternatively reduce butanone to butan-2-ol, convert to 2-bromobutane (HBr), then SN2 substitution to carboxylic acid is not direct. Accept any valid 2-step route with correct intermediates [1]
(e) Strong absorption at ~1715 cm⁻¹ (C=O stretch of ketone) [1]; absence of broad O–H absorption at 2500–3300 cm⁻¹ (not a carboxylic acid) and absence of 2720 cm⁻¹ (not an aldehyde C–H) [1]
(b) Butanone (methyl ethyl ketone); CH₃COCH₂CH₃ [1+1]
(c) Nucleophilic addition / reduction [1]; Butan-2-ol [1]
(d) Step 1: Butanone → butan-2-ol (NaBH₄, aq. ethanol) [1]
Step 2: Butan-2-ol → butanone → (only ketone, can’t oxidise further to acid easily from here; instead note: to make butanoic acid from a ketone requires a different route)
Better answer: Oxidise using acidified K₂Cr₂O₇ under vigorous conditions — ketones resist further oxidation, so you cannot make butanoic acid directly from butanone in one step [1 for recognising this complication]; alternatively reduce butanone to butan-2-ol, convert to 2-bromobutane (HBr), then SN2 substitution to carboxylic acid is not direct. Accept any valid 2-step route with correct intermediates [1]
(e) Strong absorption at ~1715 cm⁻¹ (C=O stretch of ketone) [1]; absence of broad O–H absorption at 2500–3300 cm⁻¹ (not a carboxylic acid) and absence of 2720 cm⁻¹ (not an aldehyde C–H) [1]
◆ A2 PAPER 3 STYLE — Synoptic Synthesis
Question 3: Multi-Step Organic Synthesis [15 marks]
Ibuprofen is an important pharmaceutical. A simplified retrosynthetic approach suggests it can be synthesised from benzene as a starting material using 5 steps.
(a) Describe the Friedel-Crafts acylation of benzene. Include: reagents, conditions, the identity of the electrophile, and an equation for electrophile formation. [4]
(b) Explain why the product of Friedel-Crafts acylation (a phenyl ketone) is a better starting point for further synthesis than the product of Friedel-Crafts alkylation. [2]
(c) A phenyl ketone is reduced to a secondary alcohol. Give reagents and conditions, and name the type of reaction. [2]
(d) Explain what is meant by a racemic mixture and why this reduction produces a racemic mixture. [3]
(e) Evaluate the sustainability of using Friedel-Crafts reactions in industrial synthesis. [4]
(a) Reagents: acyl chloride (RCOCl) + anhydrous AlCl₃ [1]; Conditions: heat under reflux, ~50°C, anhydrous [1]; Electrophile: acylium ion (RCO⁺) [1]; Formation: AlCl₃ + RCOCl → RCO⁺ + AlCl₄⁻ [1]
(b) Acylation introduces a C=O group (reactive, predictable) and gives a pure single product; alkylation can give poly-alkylated products (further substitution occurs more easily) and is harder to control. [1+1]
(c) NaBH₄ (sodium borohydride) in aqueous ethanol, room temperature [1]; Nucleophilic addition / reduction [1]
(d) Racemic mixture: an equimolar mixture of both enantiomers (non-superimposable mirror images) — has no overall optical activity [1]; The reduction creates a new chiral centre at the carbon bearing OH [1]; NaBH₄ attacks the planar C=O from either face with equal probability, giving equal amounts of R and S enantiomers [1]
(e) Negatives: AlCl₃ is used in stoichiometric amounts (not catalytic), generating large amounts of AlCl₄⁻ waste [1]; Acyl chlorides generate HCl gas (toxic, corrosive) [1];
Positives: reaction is efficient (high atom economy if using acyl chloride directly) [1]; conditions can be mild (room temp for some reactions) [1];
Overall evaluation: significant green chemistry concerns due to stoichiometric AlCl₃ and toxic byproducts — industry seeks alternative Brønsted or solid acid catalysts [1 for developed evaluation]
(b) Acylation introduces a C=O group (reactive, predictable) and gives a pure single product; alkylation can give poly-alkylated products (further substitution occurs more easily) and is harder to control. [1+1]
(c) NaBH₄ (sodium borohydride) in aqueous ethanol, room temperature [1]; Nucleophilic addition / reduction [1]
(d) Racemic mixture: an equimolar mixture of both enantiomers (non-superimposable mirror images) — has no overall optical activity [1]; The reduction creates a new chiral centre at the carbon bearing OH [1]; NaBH₄ attacks the planar C=O from either face with equal probability, giving equal amounts of R and S enantiomers [1]
(e) Negatives: AlCl₃ is used in stoichiometric amounts (not catalytic), generating large amounts of AlCl₄⁻ waste [1]; Acyl chlorides generate HCl gas (toxic, corrosive) [1];
Positives: reaction is efficient (high atom economy if using acyl chloride directly) [1]; conditions can be mild (room temp for some reactions) [1];
Overall evaluation: significant green chemistry concerns due to stoichiometric AlCl₃ and toxic byproducts — industry seeks alternative Brønsted or solid acid catalysts [1 for developed evaluation]
Chemical Tests & Analysis of Unknown Compounds
Identification is a major exam skill. Know the test, the observation, and what it proves. Learn by functional group — not by memorising isolated facts.
🧪 DISTINGUISHING ALDEHYDES vs KETONES
Tollens’ reagent (Ag⁺/NH₃)Silver mirror = ALDEHYDE
Fehling’s solutionBrick-red ppt = ALDEHYDE
2,4-DNP (Brady’s reagent)Orange ppt = C=O present (both!)
⚠️ 2,4-DNP cannot distinguish aldehyde from ketone — only confirms C=O exists
🧪 IDENTIFYING HALOGENS IN HALOALKANES
TestAgNO₃(aq) after hydrolysis with NaOH
Cl presentWhite ppt AgCl (soluble in dil. NH₃)
Br presentCream ppt AgBr (soluble in conc. NH₃)
I presentYellow ppt AgI (insoluble in NH₃)
Acidify with dilute HNO₃ before adding AgNO₃ to remove interfering ions
🧪 TESTING FOR FUNCTIONAL GROUPS
Bromine waterDecolourised = C=C (alkene) or phenol
Acidified K₂Cr₂O₇Orange→green = oxidisable (1°/2° alcohol or aldehyde)
Na metalFizzes/H₂ gas = OH present (alcohol or carboxylic acid)
Na₂CO₃Fizzes/CO₂ = carboxylic acid (more acidic than alcohol)
FeCl₃ solutionPurple colour = phenol
🌡️ IR SPECTROSCOPY KEY ABSORPTIONS
~3200–3550 cm⁻¹ (broad)O–H stretch (alcohol)
~2500–3300 cm⁻¹ (very broad)O–H stretch (carboxylic acid)
~1700–1750 cm⁻¹C=O stretch (aldehyde/ketone/ester)
~1715 cm⁻¹C=O ketone
~1735 cm⁻¹C=O ester
~2720 cm⁻¹C–H aldehyde (weak, characteristic)
~3300 cm⁻¹ (medium)N–H stretch (amine/amide)
⚖️ MASS SPECTROMETRY
M⁺ (molecular ion)Relative molecular mass
M+1 peak¹³C isotope presence
M+2 peak (same size as M)Bromine present (⁷⁹Br:⁸¹Br = 1:1)
M+2 peak (1/3 of M)Chlorine present (³⁵Cl:³⁷Cl = 3:1)
Loss of 15 from M⁺Loss of CH₃ group
Loss of 29 from M⁺Loss of CHO (aldehyde)
m/z = 77Phenyl cation C₆H₅⁺
🔑 DEDUCTION STRATEGY FOR UNKNOWNS
1. Use MS to get Mr and check for halogen isotope patterns.
2. Use IR to identify key functional groups (C=O, O–H, N–H).
3. Calculate degree of unsaturation if needed.
4. Use chemical tests to confirm and distinguish.
5. Draw possible structures and eliminate using all data.
Key rule: Assign a functional group ONLY when you can cite specific evidence for it.
2. Use IR to identify key functional groups (C=O, O–H, N–H).
3. Calculate degree of unsaturation if needed.
4. Use chemical tests to confirm and distinguish.
5. Draw possible structures and eliminate using all data.
Key rule: Assign a functional group ONLY when you can cite specific evidence for it.
12-Week Mastery Study Planner
Based on spaced repetition and interleaving science. Each week builds on the last, with cumulative review built in. Target: 90%+ by Week 12.
📐 HOW TO USE THIS PLANNER
Each session = 45 minutes. Do 3 sessions/week minimum. Start every session with a 5-min free recall of last week’s content before looking at notes. End every session with flashcard review on the current topic.
WEEK 1 — Chunk A
- Alkanes: FRS mechanism, cracking types
- Alkenes: all addition reactions + Markovnikov
- Daily: 5 flashcards, free recall at end
WEEK 2 — Chunk B
- Halogenoalkanes: SN1 vs SN2 vs elimination
- Rate of hydrolysis (C–X bond strength)
- Review Week 1 (10 min before new content)
WEEK 3 — Chunk C
- Alcohols: oxidation routes, dehydration
- Esterification conditions
- Interleave: mix Chunk A+B flashcards
WEEK 4 — Chunk D
- Carbonyls: NaBH₄, Tollens’, Fehling’s, DNP
- Distinguish aldehyde vs ketone
- Full free-recall sheet: Chunks A–C
WEEK 5 — Chunk E
- Carboxylic acids + acyl chlorides
- Ester hydrolysis (acid and base)
- Interleave: all 5 chunks in flashcards
WEEK 6 — Chunk F
- Amines: preparation, basicity
- Amides and polymerisation
- Full free-recall all reactions so far
WEEK 7 — Chunk G (A2)
- Benzene: structure, electrophilic substitution
- Nitration, halogenation, Friedel-Crafts
- Past paper: Topic 6 questions only
WEEK 8 — Chunk H (A2)
- Grignard reagents: formation + reactions
- Synthesis extension reactions (+C chain)
- Interleave all flashcards (random order)
WEEK 9 — Analysis
- IR, MS: all key absorptions
- Chemical tests: all functional group tests
- Practice: unknown compound deduction Qs
WEEK 10 — Synthesis Routes
- Multi-step synthesis (2–4 step problems)
- Retrosynthesis approach (work backwards)
- Do all Practice Qs in mixed order
WEEK 11 — Exam Practice
- Past Edexcel Paper 2 & 3 questions
- Time yourself (1.2 min/mark)
- Error log: record every mistake and why
WEEK 12 — Consolidation
- Target weak areas from error log
- Final free-recall: all 50+ reactions
- Full mock paper under exam conditions
📊 SELF-ASSESSMENT CHECKPOINTS
Week 4: Can recall all AS reactions without notes?
Week 8: Can draw the full pathway map from memory?
Week 10: Can plan a 4-step synthesis route in 5 minutes?
Week 12: Scoring 85%+ on timed past paper questions?