Reaction of Grignard reagent, C₂H₅MgBr with C₈H₈O followed by hydrolysis gives compound "A" which reacts instantly with Lucas reagent to give compound B, C₁₀H₁₃Cl. The Compound B is :

Solution

Chemistry ma’am · 5 steps

Read C8H8O as acetophenone: the ethyl Grignard turns it into a tertiary alcohol, and Cl takes the OH's place.

1. Identify C8H8O. C₈H₈O has 5 degrees of unsaturation: 4 for a benzene ring and 1 for a C=O. The compound that fits and gives an instant Lucas result later is acetophenone, C₆H₅COCH₃.
2. Grignard addition. The ethyl group of C₂H₅MgBr adds to the carbonyl carbon. Hydrolysis then gives A, 2-phenylbutan-2-ol, where one carbon carries OH, CH₃, C₂H₅ and C₆H₅.

   C₆H₅COCH₃ →(1. C₂H₅MgBr, 2. H₃O⁺) C₆H₅C(OH)(CH₃)C₂H₅ →(conc. HCl, ZnCl₂) C₆H₅C(Cl)(CH₃)C₂H₅

3. Why instant. A is a tertiary and benzylic alcohol. Its carbocation is very stable, so the Lucas reagent turns it cloudy at once. The Cl goes onto the same carbon that held the OH.
4. Check formula. B has 6 + 1 + 1 + 2 = 10 carbons and 5 + 3 + 5 = 13 hydrogens, so it is C₁₀H₁₃Cl, as given.
5. So. B is 2-chloro-2-phenylbutane, where Cl, CH₃, C₂H₅ and phenyl are all on one carbon. That is option (c).

The idea to keep. A Grignard reagent on a ketone always gives a tertiary alcohol. Only tertiary or benzylic alcohols react instantly with Lucas reagent, and the Cl sits exactly where the OH was.

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