Question
The R/S configuration of C - 2 and C - 3 in the given molecule will be :
This question was previously asked in
CUET PG 2026 Agri-Business Management Question Paper (25-Mar-2026) (Shift 2)
The correct answer is
(2S, 3R)
To determine the R/S configuration of C-2 and C-3 in the given molecule, we need to assign priorities to the substituents attached to each chiral center based on the Cahn-Ingold-Prelog (CIP) priority rules and then apply the sequence rule.
- Identify the chiral centers: In the given molecule, both C-2 and C-3 are chiral centers.
- Assign priorities: According to the CIP rules, the priorities are assigned based on the atomic number of the atoms directly attached to the chiral center. The higher the atomic number, the higher the priority.
- C-2 Configuration:
- At C-2, the substituents are CH3 (methyl), H (hydrogen), Cl (chlorine), and CH2CH3 (ethyl).
- Priority is assigned as follows: Cl > CH2CH3 > CH3 > H.
- Arrange with the lowest priority group (H) pointing away.
- The sequence Cl → CH2CH3 → CH3 is clockwise, which corresponds to the S configuration.
- C-3 Configuration:
- At C-3, the substituents are CH3 (methyl), H (hydrogen), Cl (chlorine), and CH2CH3 (ethyl).
- Priority is the same: Cl > CH2CH3 > CH3 > H.
- Arrange with the lowest priority group (H) pointing away.
- The sequence Cl → CH2CH3 → CH3 is counterclockwise, which corresponds to the R configuration.
Thus, the configuration of C-2 and C-3 is (2S, 3R).
This reasoning leads us to the correct answer: (2S, 3R).
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