Question 1
Multiple choiceHard1 markThe alkane shown reacts with under UV light. Which sequence shows initiation followed by the two propagation steps in which one H atom at C2 is replaced by Cl? A dot denotes one unpaired electron.
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Answer: C. UV light causes homolytic fission of producing two chlorine radicals. A chlorine radical abstracts H from C2, forming and This radical reacts with to form and regenerate sustaining the chain. A: abstracts H at a terminal carbon, so the product is 1-chloropropane. B: uses radical–radical combination, a termination step that consumes the radicals rather than regenerating one. D: shows heterolytic fission, producing ions rather than the radicals needed to initiate the chain. Remember: a propagation step consumes one radical and produces another.