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Edexcel International A Level Chemistry

Topic 18
Arenes

Topic 18 follows Transition Metals in Unit 5. It covers the structure of benzene: the Kekulé and delocalised models, the overlap of p orbitals into a π system, and the thermochemical, X-ray diffraction and infrared evidence for the delocalised ring; why benzene resists bromination compared with alkenes; the reactions of benzene with oxygen, bromine, a nitrating mixture, fuming sulfuric acid and the Friedel–Crafts reagents; the electrophilic substitution mechanisms for halogenation, nitration and Friedel–Crafts reactions, including the generation of each electrophile; and the reaction of phenol with bromine water.

Exam Unit
Unit 5
WCH15/01 – IAL
Specification Points
18.1 – 18.6
19 points covered
Sub-topics
8 lessons
Revision notes available
Exam Board
Edexcel IAL
Pearson International

Revision Notes

8 revision notes, in the order the specification teaches them.

A benzene ring with delocalised electrons
1

Structure and Bonding in Benzene

The structure and bonding of benzene: the Kekulé and delocalised models, p-orbital overlap, the π system and how benzene is represented.

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A ring of alternating bonds beside a real delocalised ring
2

Evidence for the Structure of Benzene

The evidence for the structure of benzene: hydrogenation enthalpies, delocalisation energy, bond lengths, infrared data and resistance to addition.

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An electrophile replacing a hydrogen on a benzene ring
3

Electrophilic Substitution in Benzene

Electrophilic substitution in benzene: substitution versus addition, the general mechanism and the delocalised intermediate.

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A benzene ring carrying a nitro group
4

Nitration of Benzene

The nitration of benzene: reagents and conditions, generation of NO₂⁺, the mechanism and the role of sulfuric acid.

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A benzene ring with one halogen and a halogen carrier
5

Halogenation of Benzene

The halogenation of benzene: the catalyst, generation of the halogen electrophile and the electrophilic substitution mechanism.

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A benzene ring gaining a new carbon group
6

Friedel–Crafts Alkylation and Acylation

Friedel–Crafts alkylation and acylation of benzene: AlCl₃ catalyst, the electrophile and the mechanism.

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A methyl side chain on a ring beside a purple solution
7

Other Reactions of Benzene

The combustion of benzene, sulfonation, with a reaction map of the arene chemistry.

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A phenol molecule with a white precipitate
8

Phenol and Bromine Water

Phenol: the activated ring, bromination to 2,4,6-tribromophenol, compared with benzene.

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Summary Map

Download, print and revise the key facts of this topic at a glance.

Summary maps

Download, print and revise the key facts of this topic at a glance.

Illustration of a summary map: compounds joined by reaction arrows
Summary map · PDF

Benzene Map

Edexcel International A Level Chemistry · Unit 5 · Topic 18

Every reaction on one A4 page: reagents, conditions and reaction type for each arrow, colour coded, with the key tests.

Download the map6 reactions · A4 portrait · print ready
Illustration of a summary map: compounds joined by reaction arrows
Summary map · PDF

Benzene Structure Map

Edexcel International A Level Chemistry · Unit 5 · Topic 18A Benzene: Structure and Stability

The whole section on one A4 page: the Kekulé and delocalised models, bond lengths, hydrogenation, bromine water, isomers and infrared.

Download the map6 key ideas + a data table · A4 portrait · print ready
Illustration of a summary map: compounds joined by reaction arrows
Summary map · PDF

Substitution and Phenol Map

Edexcel International A Level Chemistry · Unit 5 · Topic 18B Electrophilic Substitution and Phenol

The whole section on one A4 page: the mechanism, nitration, halogenation, Friedel-Crafts reactions, combustion, sulfonation and phenol.

Download the map6 key ideas + a data table · A4 portrait · print ready

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Written, drawn and worked exam practice on this topic.

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Revision Game

Match reagents to products, free, with your board's reagents and conditions.

Illustration of memory game cards, two turned face up as a matching pairFree

Revision Game: Arenes

Turn the cards over two at a time: match reagents to what they make, and find how each product is made.

A free memory game on the reactions in this topic, with your board's reagents, conditions and spec points.

  • Two ways to playMatch each set of reagents to what the reaction makes, or see a product and find the reactant and reagents that make it.
  • Drawn the way the exam draws themEvery structure is drawn in ChemDraw, with the reagents and conditions your exam board asks for.
  • It countsRounds earn XP and keep your streak going, and every correct match shows in your KASP analytics, apart from your marks.

Study Cards

Pick a deck, then turn each card to check what you remember.

Specification

Every specification point in this topic, in the exam board's own words. Rate how confident you are with each one.

Official Pearson Edexcel IAL documentsSpecification (opens the Pearson Edexcel IAL website in a new tab)Data booklet (opens the Pearson Edexcel IAL website in a new tab)

Self-assessment · 19 points

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18.1

  1. a

    be able to use thermochemical data as evidence for the structure and stability of the benzene ring

    Revise
  2. b

    be able to use X-ray diffraction data as evidence for the structure and stability of the benzene ring

    Revise
  3. c

    be able to use infrared data as evidence for the structure and stability of the benzene ring

    Revise
  4. d

    know acceptable representations of benzene structure in equations and mechanisms

    Revise

18.2

  1. a

    understand that the delocalised model of benzene involves overlap of p-orbitals

    Revise
  2. b

    understand that overlap of p-orbitals forms π-bonds in benzene

    Revise

18.3

  1. a

    understand why benzene is resistant to bromination compared to alkenes

    Revise
  2. b

    understand benzene resistance to bromination in terms of delocalisation of π-bonds compared with localised alkene π-bond electron density

    Revise

18.4

  1. i

    know the following reactions of benzene, limited to: oxygen in air (combustion to form a smoky flame)

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  2. ii

    know the following reactions of benzene, limited to: bromine, in the presence of a catalyst

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  3. iii

    know the following reactions of benzene, limited to: a mixture of concentrated nitric and sulfuric acids

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  4. iv

    know the following reactions of benzene, limited to: fuming sulfuric acid

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  5. v a

    know the Friedel-Crafts alkylation reaction of benzene with halogenoalkanes using aluminium chloride as catalyst

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  6. v b

    know the Friedel-Crafts acylation reaction of benzene with acyl chlorides using aluminium chloride as catalyst

    Revise

18.5

  1. a

    understand electrophilic substitution mechanism of benzene in halogenation, including generation of the electrophile

    Revise
  2. b

    understand electrophilic substitution mechanism of benzene in nitration, including generation of the electrophile

    Revise
  3. c

    understand electrophilic substitution mechanism of benzene in Friedel-Crafts reactions, including generation of the electrophile

    Revise

18.6

  1. a

    understand the reaction of phenol with bromine water

    Revise
  2. b

    understand why phenol reacts more readily with bromine water than benzene

    Revise