An organic compound (A) (molecular formula C₆H₁₂O₂) was hydrolysed with dil. H₂SO₄ to give a carboxylic acid (B) and an alcohol (C). ‘C’ gives white turbidity immediately when treated with anhydrous ZnCl₂ and conc. HCl. The organic compound (A) is :

Solution

Chemistry ma’am · 3 steps

Instant Lucas turbidity means a tertiary alcohol, so pick the ester whose alcohol part is tert-butyl.

1. Ester hydrolysis. All four options are esters of formula C₆H₁₂O₂. Dilute acid splits an ester RCOOR' into the acid RCOOH and the alcohol R'OH. So alcohol C comes from the group on the single-bonded oxygen.
2. Read the Lucas test. Anhydrous ZnCl₂ and conc. HCl turn the alcohol into an insoluble alkyl chloride through a carbocation, and this chloride makes the mixture cloudy. A tertiary carbocation is the most stable, so a tertiary alcohol turns cloudy at once. A secondary alcohol takes about 5 minutes, and a primary alcohol shows no turbidity at room temperature.

   Option	Ester	Alcohol C	Type	Lucas test
   (a)	sec-butyl ethanoate	butan-2-ol	2°	turbid in about 5 min
   (b)	propyl propanoate	propan-1-ol	1°	no turbidity at room temperature
   (c)	isobutyl ethanoate	2-methylpropan-1-ol	1°	no turbidity at room temperature
   (d)	tert-butyl ethanoate	2-methylpropan-2-ol, (CH₃)₃COH	3°	turbid immediately

3. So. Only (d) gives a tertiary alcohol. Hydrolysis gives ethanoic acid (B) and tert-butyl alcohol (C), which turns cloudy at once, so A is tert-butyl ethanoate.

The idea to keep. In the Lucas test, turbidity tracks carbocation stability: tertiary turns cloudy at once, secondary in about 5 minutes, primary not at room temperature. For an ester, check the alkyl group on the oxygen.

Answer from the NTA final answer key. Solution by PrepWiser.