Reactions of Alkanes
Use this landing page to move quickly between the main alkane reaction revision pages for Topic 4. Each card links to a focused page covering free radical substitution and the individual mechanism stages students need to understand.
Choose a Reactions of Alkanes Page
Alkanes are relatively unreactive because they contain strong non-polar C–C and C–H bonds. Their key reaction in Topic 4 is free radical substitution, where ultraviolet light generates radicals that replace hydrogen atoms with halogen atoms.
Key idea: Free radical substitution is a chain reaction. Initiation produces radicals, propagation forms products while regenerating radicals, and termination removes radicals by combining them.
Free Radical Substitution
Revise the overall reaction between alkanes and halogens, including substitution, UV light and halogenoalkane formation.
Initiation
Learn how ultraviolet light breaks the halogen-halogen bond by homolytic fission to produce reactive halogen radicals.
Propagation
Review the two propagation steps where radicals react with alkane molecules and regenerate new radicals to continue the chain.
Termination
Revise how two radicals combine to form a stable molecule, removing radicals and stopping the chain reaction.
Further Substitution
Learn why more than one hydrogen atom can be replaced, leading to mixtures of halogenated organic products.
How to Use These Pages
Start with the overview page on free radical substitution to understand the reaction type. Then work through initiation, propagation and termination in order. Finish with further substitution so you can explain why alkane halogenation can produce a mixture of products.
Exam focus: Learn the role of UV light, use curly arrows correctly for homolytic fission, include radical dots, and distinguish clearly between initiation, propagation and termination equations.
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.