JEE Advanced 2023 · Paper 1 · Chemistry Q2

ChemistryMultiple correct+4 / -2Question 36 of 51

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

The correct statement(s) about P, Q, R, and S is(are)

Both P and Q have asymmetric carbon(s).

Both Q and R have asymmetric carbon(s).

Both P and R have asymmetric carbon(s).

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

Answer and worked solution

Official answer: C, D

The products.

P: PhMgBr adds to the nitrile; hydrolysis gives the ketone $\ce{CH3CH2CH(CH3)CH2COPh}$ . A second PhMgBr gives $\ce{CH3CH2CH(CH3)CH2C(OH)Ph2}$ .
Q: Friedel-Crafts acylation gives acetophenone; PhMgBr then gives $\ce{Ph2C(OH)CH3}$ .
R: The cadmium reagent gives the ketone $\ce{CH3CH2COCH2Ph}$ ; PhMgBr then gives $\ce{CH3CH2C(OH)(Ph)CH2Ph}$ .
S: The steps run $\ce{PhCH2CH(OH)Ph}$ → $\ce{PhCH2COPh}$ → cyanohydrin $\ce{PhCH2C(OH)(CN)Ph}$ . Hot $\ce{H2SO4}$ then dehydrates it and hydrolyses the nitrile, giving $\ce{PhCH=C(Ph)COOH}$ .

Asymmetric carbons.

P: yes. The $\ce{CH(CH3)}$ carbon carries H, $\ce{CH3}$ , $\ce{C2H5}$ and $\ce{CH2C(OH)Ph2}$ .
Q: no. The carbinol carbon has two phenyls.
R: yes. The carbinol carbon carries OH, Ph, $\ce{C2H5}$ and $\ce{CH2Ph}$ .
S: no. It is an alkene acid with no $sp^3$ stereocentre.

So (C) and (D) are correct. (A) and (B) fail because Q is achiral.

JEE Advanced 2023 · Paper 1, Chemistry question 2