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GATE 2023 CY – Question 49

Organic Chemistry · Stereochemistry: Chirality and symmetry of organic molecules with or without chiral centres and determination of their absolute configurations and optical purity. Relative stereochemistry in compounds having more than one stereogenic centre. Homotopic, enantiotopic and diastereotopic atoms, groups and faces. Conformational analysis of acyclic and cyclic compounds. Geometrical isomerism and optical isomerism. Configurational and conformational effects, atropisomerism, and neighbouring group participation on reactivity and selectivity/specificity. Stereoselective and stereospecific synthesis. Enantiomeric excess. · 2 marks · Multiple select

The stereoisomer(s) of G giving the depicted product is(are)

Diagram for GATE 2023 CY question 49
  1. Structure A
  2. Structure B
  3. Structure C
  4. Structure D

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Show answer and explanation

Correct answer: (A) Structure A; (C) Structure C

Explanation

Lewis acid activates the OH group and promotes acidic Peterson elimination. The required stereoelectronic arrangement removes OH and SiMe3 anti-periplanar. Newman projection about their adjacent C–C bond maps the stereoisomers A and C to the depicted E/Z alkene; B/D give the other geometry. **Select A, C**; rotation alone cannot change relative configuration.