Reactions of Alkanes
Use this landing page to move quickly between the main alkane reaction revision pages for AQA A Level Chemistry AQA 3.3.2. These pages break free radical substitution into the overall mechanism, initiation, propagation, termination and further substitution so students can revise the radical chain process step by step.
Choose a Reactions of Alkanes Page
Alkanes are relatively unreactive because C-C and C-H bonds are strong and essentially non-polar. Their key organic reaction in this section is free radical substitution with halogens, which occurs through a chain mechanism involving initiation, propagation and termination steps.
Key idea: Free radical substitution depends on homolytic bond fission and radical chain reactions. Initiation forms radicals, propagation keeps the chain going and termination removes radicals by combining them.
Free Radical Substitution
Revise the overall reaction type, why radicals are formed and how halogenation replaces a hydrogen atom in an alkane.
Start revisingInitiation
Learn how ultraviolet light causes homolytic fission of a halogen molecule to form two reactive halogen radicals.
Start revisingPropagation
Review the two repeating steps that produce the organic product and regenerate a radical so the chain reaction continues.
Start revisingTermination
Revise how two radicals combine to form a stable molecule, removing radicals and stopping that part of the chain.
Start revisingFurther Substitution
Learn how substitution can continue to form mixtures of products when more hydrogen atoms are replaced by halogen atoms.
Start revisingHow to Use These Pages
Start with the free radical substitution overview to understand the complete mechanism. Then revise initiation, propagation and termination separately before finishing with further substitution. For each page, practise writing curly half-arrow radical equations and identifying which step of the mechanism is being shown.
Exam focus: Be able to write initiation, propagation and termination equations for alkane halogenation, use radical dots correctly and explain why a mixture of substituted products can form.
Master Introduction to Organic Chemistry and Alkanes for AQA A Level Chemistry
Continue from these free revision notes into the full 3.3.1 and 3.3.2 Introduction to Organic Chemistry and Alkanes course. The six guided video lessons are ready now; the AQA MCQ bank, teacher-marked short-answer questions, supplementary lessons and KASP spec-point report are being written, and the course opens for enrolment as soon as they are complete.
Guided video teaching
Learn the chemistry and exam technique through structured video lessons with worked examples and walkthroughs.
Instant MCQ feedback
Auto-marked MCQ quizzes provide immediate diagnostic feedback for every answer choice.
Teacher-marked SAQs
Submit written exam responses and receive chemistry specialist feedback with improvement guidance.
Progress tracking
Identify strengths and weaknesses across the full 3.3.1 and 3.3.2 specification with targeted reporting.
See how the course works
Click play to start the course preview animation.
Some ionic radii are shown.
| Ion | Ionic radius / nm |
|---|---|
| Na+ | 0.102 |
| K+ | 0.138 |
| F− | 0.133 |
| Cl− | 0.180 |
Which compound has the strongest ionic bonding?
Explain why the metallic bonding in magnesium is much stronger than that in sodium.
Copyright notice: This revision page, including its written explanations, layout and teaching sequence, is produced for Online Learning System by Dr. Mohammed Al-Fatah. It is intended for student revision and may not be copied, redistributed or republished without permission.
Keep this note — free
Save your progress across every AQA topic. A free account remembers which topics you have covered, saves your question scores, and syncs across your phone and laptop.
- Track every topic you have finished
- Keep your practice-question scores
- No payment, no card, free forever
Already registered? Log in