Alcohols
The order of reactivity of alcohols with HCl-ZnCl₂ (Lucas reagent) is:
Select the correct option:
Solution
3° > 2° > 1°
The Lucas Test distinguishes between primary, secondary, and tertiary alcohols using a mixture of concentrated HCl and anhydrous ZnCl2.
- The reaction follows an SN1 mechanism through a carbocation intermediate.
- Reactivity Order: 3∘ (Tertiary) >2∘ (Secondary) >1∘ (Primary).
- Observation:
- 3∘ Alcohols: Form turbidity (alkyl chloride) immediately.
- 2∘ Alcohols: Form turbidity in 5-10 minutes.
- 1∘ Alcohols: Do not produce turbidity at room temperature; reaction occurs only upon heating.
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About This Question
- Subject
- chemistry
- Chapter
- organic compounds containing oxygen
- Topic
- alcohols
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
3° > 2° > 1°
The Lucas Test distinguishes between primary, secondary, and tertiary alcohols using a mixture of concentrated HCl and anhydrous ZnCl2.
- The reaction follows an SN1 mechanism through a carbocation intermediate.
- Reactivity Order: 3∘ (Tertiary) >2∘ (Secondary) >1∘ (Primary).
- Observation:
- 3∘ Alcohols: Form turbidity (alkyl chloride) immediately.
- 2∘ Alcohols: Form turbidity in 5-10 minutes.
- 1∘ Alcohols: Do not produce turbidity at room temperature; reaction occurs only upon heating.
This easy difficulty chemistry question is from the chapter organic compounds containing oxygen, covering the topic of alcohols. It appeared in the 2025 exam.
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