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The order of reactivity of alcohols with a given haloacid (HCl, HBr, HI) is:
AAllylic = Benzylic only
BPrimary > Secondary > Tertiary
CTertiary > Secondary > Primary (3° > 2° > 1°)
DPrimary = Secondary = Tertiary
Answer & Solution
Correct answer: C. Tertiary > Secondary > Primary (3° > 2° > 1°)
Reactivity with HX follows **3° > 2° > 1°**. Mechanism is SN1 — proceeds via a **carbocation**, and tertiary carbocations are most stable. Primary alcohols + HCl need **ZnCl₂ catalyst** (Lucas reagent); tertiary alcohols react at room temp without catalyst.
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