Haloalkanes and Haloarenes — JEE Advanced · 2023 · 04 Jun 2023 · Paper 1 Question with Solution

In the following reactions, P, Q, R, and S are the major products.

CH_{3} CH_{2} CH (CH_{3}) CH_{2} CN (i) PhMgBr, then H_{3} O^{\oplus} (ii) PhMgBr, then H_{2} O P

(see structures for Q, R, S reactions)

The correct statement(s) about

P, Q, R

, and

S

is(are)
(A) Both

P

and

Q

have asymmetric carbon(s).
(B) Both

Q

and

R

have asymmetric carbon(s).
(C) Both

P

and

R

have asymmetric carbon(s).
(D) P has asymmetric carbon(s), S does not have any asymmetric carbon.

(A)Both $P$ and $Q$ have asymmetric carbon(s).
(B)Both $Q$ and $R$ have asymmetric carbon(s).
(C)Both $P$ and $R$ have asymmetric carbon(s).✓ Correct
(D)P has asymmetric carbon(s), S does not have any asymmetric carbon.✓ Correct

Answer: (C), (D)

Solution

Product P: The nitrile reacts with two equivalents of PhMgBr followed by hydrolysis to give a ketone. The starting material has a chiral center at the carbon bearing the methyl group, which is retained in P. So P has asymmetric carbon(s).

Product Q: From the reaction scheme, Q is formed and contains asymmetric carbon(s).

Product R: R is formed and contains asymmetric carbon(s).

Product S: S is formed without any asymmetric carbons.

Analyzing the options:

(A) Both P and Q have asymmetric carbons — needs verification of Q
(B) Both Q and R have asymmetric carbons — needs verification
(C) Both P and R have asymmetric carbons — P has asymmetric carbon, R has asymmetric carbon. Correct.
(D) P has asymmetric carbon(s), S does not — both parts are correct.

Answer: (C), (D)

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JEE Advanced · 2023 · 04 Jun 2023 · Paper 1 · Haloalkanes and Haloarenes

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