Unit 3 · Organic Chemistry (AS & A Level)
The Complete Cambridge International AS & A Level Chemistry (9701) Guide · Cambridge International AS & A Level Chemistry (9701)Unit 3 · Organic Chemistry (AS & A Level)
- The Complete Cambridge International AS & A Level Chemistry (9701) Guide
- Cambridge International AS & A Level Chemistry (9701)
- 4 sections
Cambridge International does not publish a per-unit weighting for this exam. Exam structure (official): AS Level: Multiple Choice (75 min, 40 questions, 31%) · AS Level Structured Questions (75 min, 46%) · Advanced Practical Skills (120 min, 23%); A Level: Multiple Choice (75 min, 40 questions, 15.5%) · AS Level Structured Questions (75 min, 23%) · Advanced Practical Skills (120 min, 11.5%) · A Level Structured Questions (120 min, 38.5%) · Planning, Analysis And Evaluation (75 min, 11.5%). Be ready to carry the same unit skills and representations into a complete answer on every paper. Organic Chemistry starts by identifying the functional group and the reacting electron pair. That choice controls the reagent, conditions, arrow direction, and expected product.
- How Cambridge International AS & A Level Chemistry (9701) assesses this Cambridge International publishes no per-unit percentage for Cambridge International A Level Chemistry; Paper 1 accounts for 31% of the AS Level total and 15.5% of the A Level total. · AS Level: Multiple Choice (75 min, 40 questions, 31%) · AS Level Structured Questions (75 min, 46%) · Advanced Practical Skills (120 min, 23%) | A Level: Multiple Choice (75 min, 40 questions, 15.5%) · AS Level Structured Questions (75 min, 23%) · Advanced Practical Skills (120 min, 11.5%) · A Level Structured Questions (120 min, 38.5%) · Planning, Analysis And Evaluation (75 min, 11.5%) · show the model with a displayed mechanism with lone pairs, charges, and curly arrows, a synthesis route with every intermediate and condition, a structural formula that makes carbon connectivity explicit, a multistep route with structures, reagents, conditions, and work-up, a nucleophilic acyl substitution mechanism with a tetrahedral intermediate, a proton NMR evidence table linking shift, integration, and splitting
- Key skills Organic Formulas, Functional Groups, Naming, Shapes and Isomerism, Characteristic Organic Reactions and Mechanism Terminology, Hydrocarbons: Alkanes, Alkenes and Addition Polymerisation, Halogenoalkanes: Nucleophilic Substitution and Elimination, Alcohols: Reactions, Classification and Oxidation, Carbonyl Compounds: Aldehydes and Ketones, Carboxylic Acids, Esters, Primary Amines and Nitriles, Organic Synthesis: Multi-Step Routes and Identifying Functional Groups, Arenes: Benzene, Electrophilic Substitution and Directing Effects (A Level), Optical Isomerism and Chirality (A Level), Halogenoarenes, Alcohols and Phenol (A Level), Carboxylic Acids, Esters and Acyl Chlorides (A Level), Amines, Phenylamine and Azo Compounds (A Level), Amides and Amino Acids (A Level), Condensation Polymerisation and Degradable Polymers (A Level), Organic Synthesis: Multi-Step Routes Across All Functional Groups (A Level)
- How to study for Unit 3 This page turns a displayed mechanism with lone pairs, charges, and curly arrows, a synthesis route with every intermediate and condition, a structural formula that makes carbon connectivity explicit, a multistep route with structures, reagents, conditions, and work-up, a nucleophilic acyl substitution mechanism with a tetrahedral intermediate, a proton NMR evidence table linking shift, integration, and splitting into one route: Identify the functional group and mark the electron-rich and electron-poor sites before drawing an arrow or naming a reagent..
- The organizing decision Choose a reaction route by tracking the carbon skeleton, functional-group change, electron source, and conditions at every step.
- What A Level adds Plan a selective organic route in which every reagent, condition, intermediate, electron movement, and work-up leads to the requested product form. Topics: Arenes: Benzene, Electrophilic Substitution and Directing Effects; Optical Isomerism and Chirality; Halogenoarenes, Alcohols and Phenol; Carboxylic Acids, Esters and Acyl Chlorides; Amines, Phenylamine and Azo Compounds; Amides and Amino Acids; Condensation Polymerisation and Degradable Polymers; Organic Synthesis: Multi-Step Routes Across All Functional Groups.
What Cambridge International AS & A Level Chemistry (9701) Unit 3 covers
Use this map to connect each assessed skill to the relationship or representation that makes it visible.
Organic Formulas, Functional Groups, Naming, Shapes and Isomerism
functional group; nucleophile; curly arrow02Characteristic Organic Reactions and Mechanism Terminology
functional group; nucleophile; curly arrow03Hydrocarbons: Alkanes, Alkenes and Addition Polymerisation
functional group; nucleophile; curly arrow04Halogenoalkanes: Nucleophilic Substitution and Elimination
functional group; nucleophile; curly arrow05Alcohols: Reactions, Classification and Oxidation
functional group; nucleophile; curly arrow06Carbonyl Compounds: Aldehydes and Ketones
functional group; nucleophile; curly arrow07Carboxylic Acids, Esters, Primary Amines and Nitriles
functional group; nucleophile; curly arrow08Organic Synthesis: Multi-Step Routes and Identifying Functional Groups
functional group; nucleophile; curly arrow09Arenes: Benzene, Electrophilic Substitution and Directing Effects (A Level)
electrophilic substitution; nucleophilic acyl substitution; chemical shift10Optical Isomerism and Chirality (A Level)
electrophilic substitution; nucleophilic acyl substitution; chemical shift11Halogenoarenes, Alcohols and Phenol (A Level)
electrophilic substitution; nucleophilic acyl substitution; chemical shift12Carboxylic Acids, Esters and Acyl Chlorides (A Level)
electrophilic substitution; nucleophilic acyl substitution; chemical shift13Amines, Phenylamine and Azo Compounds (A Level)
electrophilic substitution; nucleophilic acyl substitution; chemical shift14Amides and Amino Acids (A Level)
electrophilic substitution; nucleophilic acyl substitution; chemical shift15Condensation Polymerisation and Degradable Polymers (A Level)
electrophilic substitution; nucleophilic acyl substitution; chemical shift16Organic Synthesis: Multi-Step Routes Across All Functional Groups (A Level)
electrophilic substitution; nucleophilic acyl substitution; chemical shiftCambridge International does not publish a per-unit weighting for this exam.
Official unit name and weighting: Cambridge International syllabus.
Organic Chemistry
Connect the published share to the unit model
Organic Chemistry starts by identifying the functional group and the reacting electron pair. That choice controls the reagent, conditions, arrow direction, and expected product.
The official information does not assign this domain its own percentage. The five-page sequence teaches mechanisms, synthesis, isomerism, and polymers without suggesting a fixed question count.
Use the 3×3 map to connect structure with transformation. Conserve atoms and charge while making every bond change explicit. A named reagent is not enough unless its condition and the functional-group change are also visible.
Start a mechanism by identifying the electron-rich and electron-poor sites, then add the charges, partial charges, and lone pairs needed to justify movement. Every curved arrow must begin at a bond or lone pair and end where the electron pair is used; show each bond made or broken and any intermediate before checking atoms, charge, and electron count. For synthesis, compare the starting and target carbon skeletons and functional groups, work backward to plausible immediate precursors, and then test a forward sequence for compatible reagents, conditions, selectivity, and work-up. The finished route must include each isolable intermediate and must not let a later reagent destroy a group installed earlier.
For this chain-extension route, audit carbon atoms and electron movement after every reaction arrow. Identify the functional group removed and formed, then decide whether the reagent and condition can make that conversion without damaging another group. Redraw each intermediate before carrying the structure forward, checking normal valence and total charge where a mechanism is shown. Include isolation or work-up whenever it determines which species enters the next step. The synthesis is complete only when the added carbon, every intermediate, and the final functional group all agree with the target.
The decision that organizes this unit
Define the system and choose the route before calculating
Choose a reaction route by tracking the carbon skeleton, functional-group change, electron source, and conditions at every step.
Identify the functional group and mark the electron-rich and electron-poor sites before drawing an arrow or naming a reagent.
Mechanism route and repair branches
Relationships to preserve
- Functional groups is shown through reactive site, reagent, condition.
- Mechanisms is shown through tail at bond or lone pair.
- Synthesis is shown through intermediate and conditions shown.
- Aromatic chemistry is shown through electrophile and substitution.
- Acyl derivatives is shown through addition then elimination.
- Nitrogen chemistry is shown through delocalisation and condition.
Representations to read
- a displayed mechanism with lone pairs, charges, and curly arrows
- a synthesis route with every intermediate and condition
- a structural formula that makes carbon connectivity explicit
- a multistep route with structures, reagents, conditions, and work-up
- a nucleophilic acyl substitution mechanism with a tetrahedral intermediate
- a proton NMR evidence table linking shift, integration, and splitting
Branches to reject
- starting a curly arrow at an atom label instead of a bond or lone pair
- listing reagents without the matching conditions or intermediate
- changing the carbon count without showing where the added or removed carbon goes
- omitting the work-up that determines whether the product is a salt or neutral compound
- drawing an electron-flow arrow without its lone-pair or bond source
- accepting a route that changes or damages the carbon skeleton unintentionally
| Key concept | Why it's hard | What scores |
|---|---|---|
| Functional groups | Similar formulas react differently | Reactive site, reagent, condition |
| Mechanisms | Arrows track pairs | Tail at bond or lone pair |
| Synthesis | Steps may change carbon count | Intermediate and conditions shown |
How Cambridge International AS & A Level Chemistry (9701) assesses Organic Chemistry (AS & A Level)
What a complete response must make visible
Match the task to evidence that a reader can audit, then check the most likely reasoning failure before finalizing the response.
| Task | Evidence to show | Hurdle |
|---|---|---|
| Organic Formulas, Functional Groups, Naming, Shapes and Isomerism | functional group; nucleophile; curly arrow | starting a curly arrow at an atom label instead of a bond or lone pair |
| Characteristic Organic Reactions and Mechanism Terminology | functional group; nucleophile; curly arrow | listing reagents without the matching conditions or intermediate |
| Hydrocarbons: Alkanes, Alkenes and Addition Polymerisation | functional group; nucleophile; curly arrow | changing the carbon count without showing where the added or removed carbon goes |
| Halogenoalkanes: Nucleophilic Substitution and Elimination | functional group; nucleophile; curly arrow | omitting the work-up that determines whether the product is a salt or neutral compound |
| Alcohols: Reactions, Classification and Oxidation | functional group; nucleophile; curly arrow | drawing an electron-flow arrow without its lone-pair or bond source |
| Carbonyl Compounds: Aldehydes and Ketones | functional group; nucleophile; curly arrow | accepting a route that changes or damages the carbon skeleton unintentionally |
| Carboxylic Acids, Esters, Primary Amines and Nitriles | functional group; nucleophile; curly arrow | starting a curly arrow at an atom label instead of a bond or lone pair |
| Organic Synthesis: Multi-Step Routes and Identifying Functional Groups | functional group; nucleophile; curly arrow | listing reagents without the matching conditions or intermediate |
| Arenes: Benzene, Electrophilic Substitution and Directing Effects (A Level) | electrophilic substitution; nucleophilic acyl substitution; chemical shift | changing the carbon count without showing where the added or removed carbon goes |
| Optical Isomerism and Chirality (A Level) | electrophilic substitution; nucleophilic acyl substitution; chemical shift | omitting the work-up that determines whether the product is a salt or neutral compound |
| Halogenoarenes, Alcohols and Phenol (A Level) | electrophilic substitution; nucleophilic acyl substitution; chemical shift | drawing an electron-flow arrow without its lone-pair or bond source |
| Carboxylic Acids, Esters and Acyl Chlorides (A Level) | electrophilic substitution; nucleophilic acyl substitution; chemical shift | accepting a route that changes or damages the carbon skeleton unintentionally |
| Amines, Phenylamine and Azo Compounds (A Level) | electrophilic substitution; nucleophilic acyl substitution; chemical shift | starting a curly arrow at an atom label instead of a bond or lone pair |
| Amides and Amino Acids (A Level) | electrophilic substitution; nucleophilic acyl substitution; chemical shift | listing reagents without the matching conditions or intermediate |
| Condensation Polymerisation and Degradable Polymers (A Level) | electrophilic substitution; nucleophilic acyl substitution; chemical shift | changing the carbon count without showing where the added or removed carbon goes |
| Organic Synthesis: Multi-Step Routes Across All Functional Groups (A Level) | electrophilic substitution; nucleophilic acyl substitution; chemical shift | omitting the work-up that determines whether the product is a salt or neutral compound |
Build nucleophilic addition from electron sources
Read each question as it appears on the exam paper, choose your answer, then tap it to see the feedback.
Practice 1: Build nucleophilic addition from electron sources
Ethanal reacts with cyanide ions and is then treated with dilute acid.
Describe the electron movement in the nucleophilic addition mechanism and state the structural formula of the organic product.
[4]Show lone pairs, charges and curly arrows.
Show the intermediate formed before protonation.
A. An arrow starts at CN⁻ and points to oxygen; the product is CH₃CH₂CN.
❌ Not quite 😭 The electron-deficient site is the carbonyl carbon, not oxygen. This product also omits the hydroxyl group formed when the alkoxide intermediate is protonated.
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B. The cyanide lone pair attacks the carbonyl carbon, the C=O π pair moves to oxygen, and protonation gives CH₃CH(OH)CN.
✅ Correct! 😊 Both arrows begin at electron pairs and the attack avoids giving carbon five bonds. Protonation of the alkoxide gives the hydroxynitrile with one additional carbon.
C. The C=O π pair attacks CN⁻, and dilute acid converts the product into CH₃CO₂H.
❌ Not quite 😭 This reverses nucleophile and electrophile: cyanide supplies the attacking electron pair. Dilute acid protonates the alkoxide here; it does not turn ethanal directly into ethanoic acid.
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D. A curly arrow starts at the carbonyl carbon and points to CN⁻; the product is CH₃CH(OH)CH₃.
❌ Not quite 😭 A curly arrow must start at a bond or lone pair, not an atom label. The proposed product replaces the nitrile group with a methyl group and does not conserve the reacting species.
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Full explanation
- Step 1The polar C=O bond makes the carbonyl carbon electron-poor, while CN⁻ has a lone pair that can act as the electron source.
- Step 2Draw one arrow from the cyanide lone pair to the carbonyl carbon and another from the C=O π bond to oxygen.
- Step 3The resulting alkoxide accepts H⁺ during treatment with dilute acid.
- Step 4Cyanide contributes one carbon, so two-carbon ethanal forms the three-carbon product CH₃CH(OH)CN.
Practice 2: Test a structure for E/Z isomerism
The alkene CH₃CH=C(CH₃)CH₂CH₃ is considered for stereoisomerism.
State whether this alkene shows E/Z isomerism. Justify your answer by referring to the groups attached to each carbon atom of the C=C bond.
[3]Make the relevant carbon connectivity clear.
A. It shows E/Z isomerism because each alkene carbon is attached to two different groups and C=C prevents free rotation.
✅ Correct! 😊 The left alkene carbon has H and CH₃; the right has CH₃ and CH₂CH₃. With two different groups on each carbon and restricted rotation, E/Z forms are possible.
B. It does not show E/Z isomerism because a CH₃ group is attached to each alkene carbon.
❌ Not quite 😭 A matching group across the double bond does not prevent E/Z isomerism. The required test is whether the two groups on each individual alkene carbon differ.
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C. It shows optical isomerism because the C=C bond is a chiral center.
❌ Not quite 😭 A carbon atom in a C=C bond is not a tetrahedral carbon with four different attached groups. Restricted rotation here supports geometric, not optical, isomerism.
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D. It does not show stereoisomerism because all of its bonds can rotate freely.
❌ Not quite 😭 Rotation about the carbon–carbon double bond is restricted. Ignoring that restriction removes the structural reason distinct spatial arrangements can persist.
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Full explanation
- Step 1Locate the C=C bond and inspect the two substituents attached to each alkene carbon separately.
- Step 2The left carbon is bonded to H and CH₃, which are different groups.
- Step 3The right carbon is bonded to CH₃ and CH₂CH₃, which are also different groups.
- Step 4Restricted rotation about C=C therefore allows two geometric arrangements, so the alkene shows E/Z isomerism.
Key terms for Unit 3: Organic Chemistry (AS & A Level)
Models, uses, and boundaries
- Mechanism Map
- Every arrow starts at electrons and ends where they are used. Use this mechanism map when the question calls for the relationship described here.
- Nucleophilic Addition
- The overall equation preserves atoms and charge. Use this nucleophilic addition when the question calls for the relationship described here.
- Synthesis
- The sequence exposes carbon-count growth. Use this synthesis when the question calls for the relationship described here.
- Isomer Check
- Connectivity distinguishes structural isomers. Use this isomer check when the question calls for the relationship described here.
- Polymer
- The repeat unit retains every substituent. Use this polymer when the question calls for the relationship described here.
- Organic Map
- Structure and conditions jointly control selectivity. Use this organic map when the question calls for the relationship described here.
- Aromatic Route
- The carbon skeleton is preserved across two transformations. Use this aromatic route when the question calls for the relationship described here.
- Acylation
- The second amine accounts for proton transfer. Use this acylation when the question calls for the relationship described here.
- Nmr Audit
- Four constraints prevent one peak deciding structure. Use this nmr audit when the question calls for the relationship described here.
- Peptide Link
- Condensation identifies linkage and water. Use this peptide link when the question calls for the relationship described here.
Cambridge International AS & A Level Chemistry (9701) Unit 3 FAQ
How much of Cambridge International AS & A Level Chemistry (9701) does Unit 3 carry?
Cambridge International does not publish a per-unit weighting for this exam.
What is the first move on a Organic Chemistry (AS & A Level) problem?
Identify the functional group and mark the electron-rich and electron-poor sites before drawing an arrow or naming a reagent.
Which relationships should I preserve?
Functional groups is shown through reactive site, reagent, condition. Mechanisms is shown through tail at bond or lone pair. Synthesis is shown through intermediate and conditions shown. Aromatic chemistry is shown through electrophile and substitution. Acyl derivatives is shown through addition then elimination. Nitrogen chemistry is shown through delocalisation and condition.
Which representations should I practice?
Practice moving among a displayed mechanism with lone pairs, charges, and curly arrows, a synthesis route with every intermediate and condition, a structural formula that makes carbon connectivity explicit, a multistep route with structures, reagents, conditions, and work-up, a nucleophilic acyl substitution mechanism with a tetrahedral intermediate, a proton NMR evidence table linking shift, integration, and splitting.
What error should I check before submitting an answer?
Check for starting a curly arrow at an atom label instead of a bond or lone pair; listing reagents without the matching conditions or intermediate; changing the carbon count without showing where the added or removed carbon goes; omitting the work-up that determines whether the product is a salt or neutral compound; drawing an electron-flow arrow without its lone-pair or bond source; accepting a route that changes or damages the carbon skeleton unintentionally.
Evidence workshop
Continue from the free model into complete practice
The full unit guide continues with the chapter’s worked examples, figures, scoring tables, and answer checks.
- Build nucleophilic addition from electron sources
- Plan a route that adds one carbon
- Distinguish connectivity, geometry, and chirality
- Map monomer bonds into repeat units
Full unit practice. Open the complete guide for the full evidence workshop and synthesis.
Related Cambridge International AS & A Level Chemistry (9701) unit guides
Cambridge International AS & A Level Chemistry (9701) Exam Guide & Review
The whole exam and its official unit sequence.01Physical Chemistry (AS & A Level)
Cambridge International does not publish a per-unit weighting for this exam.02Inorganic Chemistry (AS & A Level)
Cambridge International does not publish a per-unit weighting for this exam.04Analysis (AS & A Level)
Cambridge International does not publish a per-unit weighting for this exam.How to study Cambridge International AS & A Level Chemistry (9701) Unit 3
Start with the organizing decision
Before solving, restate the decision in operational terms: Choose a reaction route by tracking the carbon skeleton, functional-group change, electron source, and conditions at every step.. Your first written move should be to Identify the functional group and mark the electron-rich and electron-poor sites before drawing an arrow or naming a reagent..
Practice the same idea in several representations
Rotate through a displayed mechanism with lone pairs, charges, and curly arrows, a synthesis route with every intermediate and condition, a structural formula that makes carbon connectivity explicit, a multistep route with structures, reagents, conditions, and work-up, a nucleophilic acyl substitution mechanism with a tetrahedral intermediate, a proton NMR evidence table linking shift, integration, and splitting. Use each representation to practice Organic Formulas, Functional Groups, Naming, Shapes and Isomerism, Characteristic Organic Reactions and Mechanism Terminology, Hydrocarbons: Alkanes, Alkenes and Addition Polymerisation, Halogenoalkanes: Nucleophilic Substitution and Elimination, Alcohols: Reactions, Classification and Oxidation, Carbonyl Compounds: Aldehydes and Ketones, Carboxylic Acids, Esters, Primary Amines and Nitriles, Organic Synthesis: Multi-Step Routes and Identifying Functional Groups, Arenes: Benzene, Electrophilic Substitution and Directing Effects (A Level), Optical Isomerism and Chirality (A Level), Halogenoarenes, Alcohols and Phenol (A Level), Carboxylic Acids, Esters and Acyl Chlorides (A Level), Amines, Phenylamine and Azo Compounds (A Level), Amides and Amino Acids (A Level), Condensation Polymerisation and Degradable Polymers (A Level), Organic Synthesis: Multi-Step Routes Across All Functional Groups (A Level), and explain what stays invariant when the surface form changes.
Turn each error into a repair check
After every attempt, audit the response for starting a curly arrow at an atom label instead of a bond or lone pair; listing reagents without the matching conditions or intermediate; changing the carbon count without showing where the added or removed carbon goes; omitting the work-up that determines whether the product is a salt or neutral compound; drawing an electron-flow arrow without its lone-pair or bond source; accepting a route that changes or damages the carbon skeleton unintentionally. Then redo only the first step that made the reasoning diverge, keeping units, direction, and model conditions visible.
Confirm current course details in the official Cambridge International syllabus for the 2025-2027 administration.
Where to go next
Return to the Cambridge International AS & A Level Chemistry (9701) to see every unit and plan your revision.