Question

Primary, secondary and tertiary alcohols can be distinguished by:

• A. Lucas test
• B. Fehling's test
• C. Tollens' test
• D. Hinsberg's test

Hint:

{Lucas Test Memory Trick:} 3° alcohol → Instant cloudiness 2° alcohol → Slow cloudiness 1° alcohol → No cloudiness (cold conditions)

Answer 1

The Correct Option is A

Concept: The
Lucas test is used to distinguish between primary, secondary, and tertiary alcohols based on their reactivity with Lucas reagent (conc. HCl + anhydrous ZnCl\(_2\)). Reaction: Alcohol \( \rightarrow \) Alkyl chloride (insoluble, turbidity appears)
Step 1: Basis of differentiation. The rate of formation of turbidity differs:

• Tertiary alcohol → Immediate turbidity
• Secondary alcohol → Turbidity in few minutes
• Primary alcohol → No turbidity at room temperature

Step 2: Eliminate incorrect options.

• Fehling's test → For aldehydes
• Tollens' test → For aldehydes
• Hinsberg's test → For amines

Step 3: Final answer. \[ \therefore \text{Correct answer = Lucas test} \]