alcohols

Question

The order of reactivity of alcohols with HCl-ZnCl₂ (Lucas reagent) is:

RankGuru · Accepted Answer

The **Lucas Test** distinguishes between primary, secondary, and tertiary alcohols using a mixture of concentrated $HCl$ and anhydrous $ZnCl_2$.
- The reaction follows an **$S_N1$ mechanism** through a carbocation intermediate.
- **Reactivity Order**: $3^\circ$ (Tertiary) $> 2^\circ$ (Secondary) $> 1^\circ$ (Primary).
- **Observation**:
1. **$3^\circ$ Alcohols**: Form turbidity (alkyl chloride) **immediately**.
2. **$2^\circ$ Alcohols**: Form turbidity in **5-10 minutes**.
3. **$1^\circ$ Alcohols**: Do not produce turbidity at room temperature; reaction occurs only upon heating.

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alcohols

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