Chemistry - STEREO ISOMERISM Question with Solution | TestHub

Numbering: Number the parent carbon chain starting from the principal functional group ($-CHO$ as C-1), which makes the two chiral centers C-2 and C-3.

Configuration at C-2: Assign priorities using Cahn-Ingold-Prelog (CIP) rules: $-OH$ (1) > $-CHO$ (2) > C-3 (3) > $-H$ (4). The lowest priority group ($-H$) is on the dash, and the path $1\to 2\to 3$ goes clockwise, giving 2R.

Configuration at C-3: Assign priorities: $-OH$ (1) > C-2 (2) > $-Et$ (3) > $-Me$ (4). The lowest priority group ($-Me$) is on the wedge, and the path $1\to 2\to 3$ goes clockwise, which inverts to 3S.

Final Answer: Combining both chiral centers gives the configuration (2R, 3S), matching Option (B).