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Reactivity of haloalkanes in SN2 by leaving group:
AI > Br > Cl > F (iodide is best leaving group; F⁻ is poor)
BF best
CAll same
DF > Cl
Answer & Solution
Correct answer: A. I > Br > Cl > F (iodide is best leaving group; F⁻ is poor)
Leaving group ability in SN2: better LG = lower basicity (weak conjugate base = stable). I⁻ (weak base) is best LG, F⁻ is poor (F⁻ basicity higher in some media). Hence R-I > R-Br > R-Cl > R-F in SN2 reactivity.
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