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AQA A Level Chemistry

Reactions of Alkenes

Alkenes react because the carbon-carbon double bond contains an electron-rich pi bond. These pages separate the key addition reactions and chemical tests so students can revise reagents, conditions, products and observations clearly.

Exam Paper
Paper 2
7405/2
Specification Points
3.3.4.2
1 point covered
Sub-topics
5 lessons
Revision notes available
Exam Board
AQA
AQA 7405

Revision Notes

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

A halogen molecule approaching a carbon-carbon double bond
1

Halogens

Revise the addition reactions of alkenes with halogens, including how the C=C bond reacts with Br₂ and Cl₂.

Start revising
A hydrogen halide molecule approaching a carbon-carbon double bond
2

Hydrogen Halide

Learn how hydrogen halides add across the C=C bond and how major products can form with unsymmetrical alkenes.

Start revising
An orange test tube beside a colourless one, the bromine water test
3

Bromine Water

Review the bromine water test for unsaturation, including the colour change from orange to colourless.

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A double bond beside a bottle of concentrated acid
4

Sulfuric Acid

Learn how concentrated sulfuric acid adds across the C=C bond to form an alkyl hydrogensulfate, and how hydrolysis then gives an alcohol.

Start revising
A steam cloud and water molecule beside a double bond
5

Steam

Learn how steam adds to alkenes to produce alcohols, including the acid-catalysed mechanism.

Start revising

Summary Map

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

Summary map

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

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

Alkenes Map

AQA A Level Chemistry · 3.3.4 Alkenes

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

Download the map5 reactions · A4 portrait · print ready

© 2026 Online Learning System. For personal study: printing is allowed; editing, copying and redistribution are not.

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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: Alkenes

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 AQA documentsSpecification (opens the AQA website in a new tab)Data booklet (opens the AQA website in a new tab)

Self-assessment · 22 points

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3.3.4.1

  1. i

    know that alkenes are unsaturated hydrocarbons

    Revise
  2. ii a

    know that bonding in alkenes involves a double covalent bond

    Revise
  3. ii b

    know that bonding in alkenes involves a centre of high electron density

    Revise

3.3.4.2

  1. i a

    know the electrophilic addition reaction of alkenes with HBr

    Revise
  2. i b

    know the electrophilic addition reaction of alkenes with H2SO4

    Revise
  3. i c

    know the electrophilic addition reaction of alkenes with Br2

    Revise
  4. ii

    know the use of bromine water to test for unsaturation

    Revise
  5. iii a

    outline the electrophilic addition mechanism for reactions of alkenes with HBr

    Revise
  6. iii b

    outline the electrophilic addition mechanism for reactions of alkenes with H2SO4

    Revise
  7. iii c

    outline the electrophilic addition mechanism for reactions of alkenes with Br2

    Revise
  8. iv a

    explain the formation of major and minor products in addition reactions of unsymmetrical alkenes

    Revise
  9. iv b

    explain the formation of products in addition reactions of unsymmetrical alkenes by reference to the relative stability of primary carbocation intermediates

    Revise
  10. iv c

    explain the formation of products in addition reactions of unsymmetrical alkenes by reference to the relative stability of secondary carbocation intermediates

    Revise
  11. iv d

    explain the formation of products in addition reactions of unsymmetrical alkenes by reference to the relative stability of tertiary carbocation intermediates

    Revise

3.3.4.3

  1. i

    know that addition polymers are formed from alkenes and substituted alkenes

    Revise
  2. ii

    know the repeating unit of addition polymers and IUPAC rules for naming them

    Revise
  3. iii a

    draw the repeating unit from a monomer structure

    Revise
  4. iii b

    draw the repeating unit from a section of the polymer chain

    Revise
  5. iv

    draw the structure of the monomer from a section of the polymer chain

    Revise
  6. v

    explain why addition polymers are unreactive

    Revise
  7. vi

    explain the nature of intermolecular forces between molecules of polyalkenes

    Revise
  8. vii

    know the typical uses of poly(chloroethene) (PVC) and how its properties can be modified using a plasticiser

    Revise