Chemistry study notes
Organic Chemistry
Read structures, reason through electron movement, and connect functional groups with the conditions that transform them.
A-Level 9476 (2026-2027)
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34 topicsA formula should tell you exactly which atoms are connected
Move between molecular, displayed, condensed, skeletal and three-dimensional representations.
Recognise the functional group before choosing a reaction
The same atom, such as nitrogen or oxygen, behaves differently in different bonding environments.
Hybrid orbitals form the sigma framework; unhybridised p orbitals form pi bonding
The local bonding pattern predicts tetrahedral, planar or linear geometry.
Isomers can differ in connectivity or in arrangement around a fixed framework
First compare which atoms are joined, then consider restricted rotation.
Chirality is non-superimposability on a mirror image
A tetrahedral centre with four different groups is a common cause, but molecular symmetry still matters.
Name the change and track where the electrons begin
Reaction classes describe the net change; mechanisms explain the individual electron movements.
Look for accessible electron-rich and electron-poor sites
Bond polarity, delocalisation and access explain why similar-looking compounds react differently.
Radical substitution is a chain reaction
Initiation makes radicals; propagation regenerates a radical; termination removes them.
An alkene donates its pi electrons to an electrophile
For bromine in a non-aqueous solvent, a bromonium intermediate is opened by bromide.
Aromatic substitution restores the delocalised ring
Benzene first forms a non-aromatic intermediate, then loses a proton to recover aromatic stabilisation.
SN2 forms and breaks bonds in one concerted step
Backside approach makes steric access and inversion central to the mechanism.
SN1 forms a carbocation before the nucleophile attacks
Carbocation stability controls ionisation; a planar intermediate loses the original stereochemical information.
Cyanide attacks the carbonyl carbon, then oxygen is protonated
The carbonyl becomes a tetrahedral hydroxynitrile centre and the carbon chain gains one carbon.
An alkene offers a reactive pi bond that an alkane lacks
Reagent and conditions determine whether the double bond adds, reduces or oxidatively breaks.
Hot oxidation reveals what was attached to each double-bond carbon
Cut C=C into two carbonyl-containing fragments, then account for further oxidation.
The ring and side-chain respond to different conditions
State the catalyst, light condition and temperature before predicting where substitution occurs.
Combustion products have different environmental effects
A catalytic converter reduces several pollutants but does not remove carbon dioxide emissions.
An aqueous nucleophile substitutes; hot ethanolic base favours elimination
Solvent, reagent and temperature select different products from the same carbon skeleton.
A covalently attached halogen must first be released before an ionic halide test
Hydrolysis distinguishes reactivity; silver nitrate identifies the released halide.
The carbon bearing OH determines the oxidation product
Distillation removes an aldehyde; reflux keeps it with oxidant long enough to form an acid.
Use a structural pattern for iodoform, and delocalisation for phenol
An OH group alone does not guarantee a positive iodoform test or phenol-like acidity.
First detect a carbonyl, then distinguish its class and methyl-carbonyl unit
No single test provides the complete structure.
Carboxylic acids are stabilised by their delocalised conjugate bases
Oxidation and nitrile hydrolysis make the group; substituents tune its acidity.
Choose between acid-base reaction and changing the acyl group
Salt formation leaves the carbon skeleton intact; reduction and substitution transform the functional group.
An acyl chloride reacts readily with water, alcohols, phenols and amines
Its polar carbonyl and leaving chloride make it more reactive than an alkyl or aryl chloride.
Acid hydrolysis is reversible; alkaline hydrolysis traps the carboxylate
Use the medium to decide whether the acid or its salt is the product.
Track every carbon when preparing an amine
Nitrile and amide reduction keep the original carbonyl or nitrile carbon in the product chain.
Basicity depends on how available the nitrogen lone pair is
Gas-phase alkyl donation and aqueous solvation answer different comparisons.
An amide nitrogen is electronically coupled to its carbonyl
Delocalisation suppresses ordinary basicity; hydrolysis and reduction break different parts of the group.
An amino acid can donate and accept protons
Its dominant charged form depends on pH; zero net charge does not mean no internal charges.
The repeat unit must preserve the correct bonds and functional groups
Addition opens a multiple bond; condensation joins functional groups while losing a small molecule.
Proteins are condensation polymers of alpha-amino acids
A peptide bond is an amide bond between the carbonyl carbon of one amino acid and nitrogen of another.
A hydrolysable link helps degradation, but conditions still determine the rate
Chemical structure, processing and collection systems all affect a material's useful life and environmental cost.
Build a route by changing one functional group at a time
Check carbon count, conditions, competing groups and the final chemical form.
Scope and references
Learning outcomes and sources
11. Organic Chemistry. Use the outcome map to find the explanation for a particular syllabus requirement.
See the learning outcome map
11.1(a) Interpret, name and represent the specified organic families.
- (i) Alkanes, alkenes, arenes
- (ii) Halogenoalkanes, halogenoarenes
- (iii) Alcohols, phenols
- (iv) Aldehydes, ketones
- (v) Carboxylic acids, acyl chlorides, esters
- (vi) Amines, amides, amino acids, nitriles
- General, molecular, empirical, structural, displayed and skeletal formulae; unambiguous aromatic representation
A formula should tell you exactly which atoms are connectedRecognise the functional group before choosing a reaction
11.1(b) Describe carbon hybridisation in the reference molecules.
- sp3 in ethane
- sp2 in ethene and benzene
- sp in ethyne
Hybrid orbitals form the sigma framework; unhybridised p orbitals form pi bonding
11.1(c) Explain the reference molecular shapes and bond angles.
- Ethane, ethene, benzene, ethyne
- Sigma and pi carbon-carbon bonds
- Tetrahedral, trigonal planar and linear geometry
Hybrid orbitals form the sigma framework; unhybridised p orbitals form pi bonding
11.1(d) Predict shape and angles in analogous molecules.
- Transfer local hybridisation and sigma/pi reasoning to unfamiliar structures
Hybrid orbitals form the sigma framework; unhybridised p orbitals form pi bonding
11.2(a) Describe constitutional isomerism.
- Same molecular formula, different connectivity
- Skeleton, position and functional-group examples
Isomers can differ in connectivity or in arrangement around a fixed framework
11.2(b) Explain cis-trans alkene isomerism.
- Restricted rotation caused by pi bonding
- Two different groups on each double-bond carbon
- E/Z nomenclature not required
Isomers can differ in connectivity or in arrangement around a fixed framework
11.2(c) Identify a chiral centre.
- Tetrahedral centre with four different groups
- Compare whole substituent groups
11.2(d) Assess molecular chirality using centres and symmetry.
- Presence/absence of chiral centres
- Plane of symmetry
- Chiral-centre count alone is insufficient
11.2(e) Connect optical activity with chiral molecules.
- Rotation of plane-polarised light
- Racemic cancellation and limits of an inactive observation
11.2(f) Compare enantiomer physical properties.
- Identical ordinary physical properties in an achiral environment
- Opposite optical rotations under matching conditions
- Diastereomer terminology not required
11.2(g) Compare enantiomer chemical properties.
- Identical with achiral environments/reagents
- Different interactions with another chiral molecule
11.2(h) Relate stereoisomerism to biological properties.
- Chiral recognition, for example in drug action
- Receptor/enzyme selectivity
11.2(i) Deduce possible isomers from a molecular formula.
- Systematic enumeration
- Constitutional and relevant stereoisomer possibilities
- Avoid duplicate rotated/relabelled drawings
Isomers can differ in connectivity or in arrangement around a fixed framework
11.2(j) Identify stereochemical features from structures.
- Chiral centres
- Cis-trans possibilities
- Use wedge/hash conventions for enantiomer drawings
Isomers can differ in connectivity or in arrangement around a fixed frameworkChirality is non-superimposability on a mirror image
11.3(a) Use the specified reaction terminology.
- (i) Functional group
- (ii) Primary, secondary, tertiary, quaternary substitution
- (iii) Homolytic/heterolytic fission
- (iv) Carbocation
- (v) Free radical
- (vi) Electrophile/Lewis acid and nucleophile/Lewis base
- (vii) Addition, substitution, elimination, condensation, hydrolysis
- (viii) Oxidation and reduction; [O]/[H] acceptable
Recognise the functional group before choosing a reactionName the change and track where the electrons begin
11.3(b) Use the specified structural-reactivity concepts.
- (i) Delocalisation
- (ii) Electron donation/withdrawal
- (iii) Steric hindrance
11.3(c) Explain alkane unreactivity.
- Strong nearly non-polar sigma bonds
- General unreactivity towards polar reagents
11.3(d) Explain alkene reactivity towards electrophiles.
- Accessible pi electron density
- Electron-pair donation
Look for accessible electron-rich and electron-poor sitesAn alkene donates its pi electrons to an electrophile
11.3(e) Compare benzene and alkene reactivity through delocalisation.
- (i) Relative electrophilic reactivity
- (ii) Benzene preference for substitution over addition
Look for accessible electron-rich and electron-poor sitesAromatic substitution restores the delocalised ring
11.3(f) Interpret halogenoalkane reactivity, especially hydrolysis.
- Relative C-Cl, C-Br, C-I strengths
- Compare otherwise similar substrates/conditions
Look for accessible electron-rich and electron-poor sitesAn aqueous nucleophile substitutes; hot ethanolic base favours elimination
11.3(g) Explain chlorobenzene resistance to nucleophilic substitution.
- Halogen lone-pair delocalisation
- Partial C-Cl double-bond character
- Steric/geometric hindrance from the aromatic framework
11.3(h) Explain carbonyl reactivity towards nucleophiles.
- Polar C=O and electrophilic carbon
- Hydrogen cyanide as the named example
Look for accessible electron-rich and electron-poor sitesCyanide attacks the carbonyl carbon, then oxygen is protonated
11.3(i) Apply reaction and reactivity concepts to mechanisms.
- Relate organic structure, bonding, electron effects and steric effects to reaction pathways
Name the change and track where the electrons beginLook for accessible electron-rich and electron-poor sites
11.3(j) Track electron flow in polar mechanisms.
- Electron-rich to electron-poor
- Curly-arrow source and destination
- Pair arrows distinguished from single-electron fishhooks
Name the change and track where the electrons beginLook for accessible electron-rich and electron-poor sites
11.3(k) Describe the free-radical substitution mechanism.
- Ethane with chlorine
- Initiation under UV
- Two propagation steps
- Termination reactions
- Radical/electron bookkeeping
11.3(l) Describe electrophilic addition of bromine to ethene.
- Br2 in CCl4
- Polarisation, electron-pair movement, bromide attack
- Bromonium intermediate and 1,2-dibromoethane product
11.3(m) Describe aromatic electrophilic substitution.
- (i) Monobromination of benzene
- AlBr3 activation and catalyst regeneration
- Sigma complex and proton loss
- (ii) Loss then restoration of pi delocalisation
11.3(n) Explain both nucleophilic-substitution mechanisms.
- (i) SN1 and carbocation stability
- (ii) SN2 and steric hindrance
- Electron arrows, intermediate versus transition state, simple rate laws
SN1 forms a carbocation before the nucleophile attacksSN2 forms and breaks bonds in one concerted step
11.3(o) Describe cyanide nucleophilic addition to carbonyl compounds.
- Aldehydes and ketones with HCN
- Carbon-end attack by CN-
- C=O electron movement, alkoxide protonation and cyanide regeneration
Cyanide attacks the carbonyl carbon, then oxygen is protonated
11.4(a) Describe alkane chemistry using ethane.
- (i) Combustion
- (ii) Cl2 and Br2 radical substitution, UV at room temperature
Radical substitution is a chain reactionAn alkene offers a reactive pi bond that an alkane lacks
11.4(b) Describe alkene chemistry using ethene and analogous structures.
- (i) Steam/H3PO4, HX gas, aqueous or CCl4 halogen addition
- (ii) H2/Ni reduction
- (iii) Cold alkaline manganate(VII) to diols
- (iv) Hot acidified manganate(VII) cleavage and double-bond-position deduction
An alkene offers a reactive pi bond that an alkane lacksHot oxidation reveals what was attached to each double-bond carbonAn alkene donates its pi electrons to an electrophileBuild a route by changing one functional group at a time
11.4(c) Apply and explain Markovnikov addition.
- Unsymmetrical alkenes with hydrogen halides
- Major/minor products
- Relative carbocation stability
An alkene donates its pi electrons to an electrophileAn alkene offers a reactive pi bond that an alkane lacks
11.4(d) Describe the specified aromatic-ring reactions.
- Benzene and methylbenzene
- (i) Cl2/AlCl3 and Br2/AlBr3; Lewis acid catalysts
- (ii) Concentrated HNO3/H2SO4; 30 C methylbenzene, 50 C benzene; Bronsted acid catalyst
- (iii) Friedel-Crafts alkylation with halogenoalkane and AlCl3/AlBr3
The ring and side-chain respond to different conditionsAromatic substitution restores the delocalised ring
11.4(e) Describe alkyl-side-chain chemistry using methylbenzene.
- (i) Cl2 or Br2, UV at room temperature
- (ii) Hot alkaline KMnO4 then dilute acid, or hot acidified KMnO4, to benzoic acid
11.4(f) Predict ring versus side-chain halogenation.
- Use light and catalyst conditions to distinguish radical and electrophilic pathways
11.4(g) Predict substitution positions in monosubstituted arenes.
- 2/4 versus 3 direction
- Electronic effect distinguished from activation and steric effects
11.4(h) Explain environmental consequences of hydrocarbon use.
- (i) Engine CO, NOx, unburnt hydrocarbons and catalytic removal
- (ii) Enhanced-greenhouse gases
- Distinguish warming, ozone depletion and local pollution
11.5(a) Describe the specified halogenoalkane reactions.
- (i) Bromoethane: NaOH(aq)/heat hydrolysis; KCN/ethanol/heat to nitrile; NH3/ethanol/heat/pressure to primary amine
- (ii) 2-bromopropane: NaOH/ethanol/heat elimination
- Predict analogous products and track carbon count
An aqueous nucleophile substitutes; hot ethanolic base favours eliminationBuild a route by changing one functional group at a time
11.5(b) Explain substitution stereochemistry for optically active substrates.
- (i) SN2 inversion
- (ii) SN1 racemisation through a planar carbocation
SN2 forms and breaks bonds in one concerted stepSN1 forms a carbocation before the nucleophile attacks
11.5(c) Distinguish organic halogen compounds experimentally.
- (i) Different halogenoalkanes
- (ii) Halogenoalkanes versus halogenoarenes
- Hydrolysis followed by halide-ion tests
A covalently attached halogen must first be released before an ionic halide test
11.5(d) Relate fluoroalkane uses to relative inertness.
- Fluoroalkanes and fluorohalogenoalkanes
- Strong C-F bonds and useful stability
A covalently attached halogen must first be released before an ionic halide test
11.5(e) Distinguish CFC and replacement environmental effects.
- CFC ozone impact
- HFC and HCFC significant environmental impacts
- Detailed ozone-depletion mechanisms not required
A covalently attached halogen must first be released before an ionic halide test
11.6(a) Describe alcohol reactions using ethanol.
- (i) Combustion
- (ii) HX or PCl5 to halogenoalkanes
- (iii) Sodium
- (iv) Acidified K2Cr2O7, heat/distillation to carbonyl; primary alcohol with acidified KMnO4 or K2Cr2O7 under reflux to acid
- (v) Concentrated H3PO4 and heat dehydration
The carbon bearing OH determines the oxidation productBuild a route by changing one functional group at a time
11.6(b) Distinguish primary, secondary and tertiary alcohols.
- Mild oxidation
- Product identity as well as oxidant colour change
11.6(c) Infer the iodoform-active alcohol unit.
- CH3CH(OH)- group, including ethanol
- Warm alkaline aqueous iodine
- Yellow tri-iodomethane
Use a structural pattern for iodoform, and delocalisation for phenol
11.6(d) Describe phenol chemistry.
- (i) Bases
- (ii) Sodium
- (iii) Dilute HNO3 to 2-/4-nitrophenol; aqueous Br2 to 2,4,6-tribromophenol
Use a structural pattern for iodoform, and delocalisation for phenol
11.6(e) Explain relative aqueous acidity of water, phenol and ethanol.
- Bronsted-Lowry interpretation
- Conjugate-base delocalisation and electron donation
Use a structural pattern for iodoform, and delocalisation for phenol
11.7(a) Interconvert alcohols and carbonyl compounds.
- Primary alcohol/aldehyde
- Secondary alcohol/ketone
- LiAlH4 or H2/Ni reduction
The carbon bearing OH determines the oxidation productBuild a route by changing one functional group at a time
11.7(b) Describe HCN addition to aldehydes and ketones.
- KCN catalyst
- Hydroxynitrile products
- Analogous structures and carbon count
Cyanide attacks the carbonyl carbon, then oxygen is protonated
11.7(c) Detect carbonyl compounds with 2,4-DNPH.
- Hydrazone precipitate
- Aldehyde/ketone scope
First detect a carbonyl, then distinguish its class and methyl-carbonyl unit
11.7(d) Distinguish aldehydes and ketones using test evidence.
- Warm Fehling and Tollens tests
- Ease of oxidation
- Named aldehyde/ketone comparisons and test limitations
First detect a carbonyl, then distinguish its class and methyl-carbonyl unit
11.7(e) Infer a methyl-carbonyl unit from iodoform.
- CH3CO-
- Warm alkaline iodine
- Ethanal, propanone and phenylethanone examples
First detect a carbonyl, then distinguish its class and methyl-carbonyl unit
11.8(a) Prepare carboxylic acids by oxidation and hydrolysis.
- Primary alcohols and aldehydes: acidified KMnO4/K2Cr2O7 under reflux
- Nitriles: dilute acid and heat or dilute alkali/heat then acidification
Carboxylic acids are stabilised by their delocalised conjugate basesThe carbon bearing OH determines the oxidation productBuild a route by changing one functional group at a time
11.8(b) Describe four carboxylic-acid transformations.
- (i) Salts with metals, alkalis, carbonates
- (ii) Alcohol/concentrated H2SO4/heat to ester; ethyl ethanoate
- (iii) PCl5 to acyl chloride; ethanoyl chloride
- (iv) LiAlH4 reduction to primary alcohol; ethanol
Choose between acid-base reaction and changing the acyl groupBuild a route by changing one functional group at a time
11.8(c) Explain carboxylic-acid and chloroethanoic-acid acidity.
- Carboxylate delocalisation
- Chlorine electron withdrawal
- Number and proximity of substituents
Carboxylic acids are stabilised by their delocalised conjugate bases
11.8(d) Describe acyl-chloride hydrolysis.
- Water to carboxylic acid and HCl
- Ease under ordinary conditions
An acyl chloride reacts readily with water, alcohols, phenols and amines
11.8(e) Describe acyl-chloride condensation reactions.
- Alcohols
- Phenols
- Primary amines
- Correct ester/amide connectivity and HCl accounting
An acyl chloride reacts readily with water, alcohols, phenols and amines
11.8(f) Compare acyl, alkyl and aryl chloride hydrolysis.
- Carbonyl electrophilicity and leaving group
- Saturated-carbon substitution
- Aryl delocalisation and steric/geometric restriction
An acyl chloride reacts readily with water, alcohols, phenols and amines
11.8(g) Prepare an ester from an acyl chloride.
- Phenyl benzoate from benzoyl chloride and phenol/phenoxide
An acyl chloride reacts readily with water, alcohols, phenols and amines
11.8(h) Describe acid and base ester hydrolysis.
- Aqueous acid or alkali and heat
- Acid versus carboxylate products
- Ethyl ethanoate and analogous ester deductions
Acid hydrolysis is reversible; alkaline hydrolysis traps the carboxylateBuild a route by changing one functional group at a time
11.9(a) Prepare the specified amines.
- Ethylamine: amide/LiAlH4 and nitrile/LiAlH4 or H2/Ni reduction
- Phenylamine: nitrobenzene/Sn/concentrated HCl/heat then NaOH(aq)
- Carbon-count and salt-form accounting
Track every carbon when preparing an amineBuild a route by changing one functional group at a time
11.9(b) Describe amine salt formation.
- Protonation with acids
- Alkylamine and phenylamine examples
11.9(c) Explain primary, secondary and tertiary amine gas-phase basicity.
- Lewis-base interpretation
- Alkyl electron donation
- Gas-phase scope
11.9(d) Compare aqueous ammonia, ethylamine and phenylamine basicity.
- Ethyl electron donation
- Phenylamine lone-pair delocalisation
- Aqueous medium distinguished from gaseous trends
11.9(e) Describe phenylamine with aqueous bromine.
- 2,4,6-Tribromophenylamine
- Decolourisation and white precipitate
- Ring activation and directing effect
11.9(f) Form amides from primary amines and acyl chlorides.
- RNH2 and R'COCl condensation
- N-substituent preserved
- HCl/excess-amine accounting
11.9(g) Explain amide neutrality.
- Nitrogen lone pair delocalised towards carbonyl
- Reduced availability for proton acceptance
11.9(h) Describe amide reactions using ethanamide.
- (i) Aqueous acid or alkali and heat hydrolysis
- (ii) LiAlH4 reduction to amine
- Medium-dependent nitrogen and carboxylic products
An amide nitrogen is electronically coupled to its carbonylBuild a route by changing one functional group at a time
11.9(i) Describe amino-acid acid-base properties.
- Aminoethanoic acid
- Zwitterion and protonation state
- Response to added acid/base
11.10(a) Recognise polymers as macromolecules built from monomers.
- Average relative molecular mass at least 1000 or at least 100 repeat units
- Chain-length distributions
The repeat unit must preserve the correct bonds and functional groups
11.10(b) Distinguish addition and condensation polymerisation.
- Poly(alkenes)
- Polyesters
- Polyamides
- Repeat-unit and monomer reconstruction
The repeat unit must preserve the correct bonds and functional groups
11.10(c) Describe protein formation by condensation.
- Alpha-amino acid monomers
- Peptide/amide bonds
- Residues and sequence
11.10(d) Describe protein hydrolysis.
- Aqueous acid or aqueous alkali and heat
- Correct amino-acid product forms
11.10(e) Explain difficulty biodegrading poly(alkenes).
- Chemical inertness of the carbon backbone
- Distinguish fragmentation from degradation
A hydrolysable link helps degradation, but conditions still determine the rate
11.10(f) Relate polyester/polyamide degradation to hydrolysis.
- Hydrolysable ester and amide links
- General biodegradability and condition-dependent rates
A hydrolysable link helps degradation, but conditions still determine the rate
11.10(g) Evaluate plastic recycling and finite resources.
- Economic factors
- Environmental factors
- Social factors
A hydrolysable link helps degradation, but conditions still determine the rate
- SEAB H2 Chemistry 9476, examination 2026
Topic 11, printed pages 23-32. The preamble, all ten subsections, all 76 outcome groups, named examples, mechanisms, precise nitration temperatures and exclusions inspected.
- SEAB H2 Chemistry 9476, examination 2027
Current 9476 course reference; this course is independently mapped rather than inheriting the outgoing 9729 organic inventory.
- Grail: H2 Organic Chemistry Summary 2026
Background comparison of reaction families and reagent tables. Explanations, examples and figures here are original; shorthand and mechanistic claims were checked against the syllabus and chemical reasoning.
- Grail: VJC Isomerism Lecture Notes, 2025
Constitutional-enumeration text and pages 6-8 on centres, symmetry and stereoisomer drawing consulted; page 7 inspected visually. The complete C4H8 search and butane-2,3-diol symmetry example here use original wording and diagrams.
- Grail: RI Halogen Derivatives, 2023
PDF pages 11-17 visually inspected for substitution arrows, transition-state conventions, inversion and two-face attack. The water-attack and chiral-substrate teaching figures here are original; current 9476 determines scope.
- Georgia Tech: Formation of halohydrins
University mechanism reference checked for bromonium formation and water as a competing nucleophile in aqueous bromination.
- OpenStax Organic Chemistry: Halohydrins from alkenes
Publisher reference checked for the solvent distinction between dibromide formation and aqueous halohydrin formation; no source figure or wording reproduced.