alleryThe C–X bond enthalpies follow the order:
AC–F < C–Cl < C–Br < C–I
BAll bond enthalpies are equal
CC–I > C–Br > C–F > C–Cl
DC–F > C–Cl > C–Br > C–I (decreases down the group)
Answer & Solution
Correct answer: D. C–F > C–Cl > C–Br > C–I (decreases down the group)
**Bond enthalpy decreases down the group**: C–F (452) > C–Cl (351) > C–Br (293) > C–I (234 kJ/mol).
**Reason:** bond length **increases** down the group as halogen size grows → weaker bond.
C–I is the weakest, so iodide is the best leaving group.
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