Alkanes
The free-radical chlorination of methane proceeds through which of the following sequence of elementary steps?
Select the correct option:
Solution
Initiation → Propagation → Termination
Free-radical halogenation is a chain reaction that proceeds in three stages. (1) Initiation: UV light or heat homolytically cleaves the Cl–Cl bond to give two Cl• radicals. (2) Propagation: Cl• abstracts H from CH₄ to give CH₃• + HCl; then CH₃• reacts with Cl₂ to give CH₃Cl + Cl•, regenerating the radical and continuing the chain. (3) Termination: two radicals combine (e.g., Cl• + Cl• → Cl₂, or CH₃• + Cl• → CH₃Cl) consuming radicals and ending the chain. The correct order is therefore Initiation → Propagation → Termination.
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More alkanes Practice Questions
Arrange the following alkyl halides in decreasing order of reactivity towards SN2 reaction: CH3I, CH...
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About This Question
- Subject
- chemistry
- Chapter
- hydrocarbons
- Topic
- alkanes
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
Initiation → Propagation → Termination
Free-radical halogenation is a chain reaction that proceeds in three stages. (1) Initiation: UV light or heat homolytically cleaves the Cl–Cl bond to give two Cl• radicals. (2) Propagation: Cl• abstracts H from CH₄ to give CH₃• + HCl; then CH₃• reacts with Cl₂ to give CH₃Cl + Cl•, regenerating the radical and continuing the chain. (3) Termination: two radicals combine (e.g., Cl• + Cl• → Cl₂, or CH₃• + Cl• → CH₃Cl) consuming radicals and ending the chain. The correct order is therefore Initiation → Propagation → Termination.
This easy difficulty chemistry question is from the chapter hydrocarbons, covering the topic of alkanes. It appeared in the 2025 exam.
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