alleryAmong alkyl halides, the order of reactivity towards nucleophilic substitution (for the same R group) is:
AR-F > R-Cl > R-Br > R-I
BR-I > R-Br > R-Cl > R-F
CR-Cl > R-Br > R-I > R-F
DAll have identical reactivity
Answer & Solution
Correct answer: B. R-I > R-Br > R-Cl > R-F
**R-I > R-Br > R-Cl > R-F**.
**Two reasons:** (i) **bond enthalpy decreases I > Br > Cl > F** (easier to break)
(ii) **iodide is a better leaving group** because of polarisability/larger size — more stable as a free anion.
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