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UPSC Combined Geo-Scientist

Chemist

  • 2 objective papers
  • 120 questions each
  • 2 h per paper
  • 100 + 300 marks

Prelims Paper II covers chemistry.

UPSC Combined Geo-Scientist, Prelims · 2025 · Paper II, Chemistry · Q87 of 120

Geo-Scientist Prelims 2025 Chemistry Q87: The Fischer projection formula and its corresponding zig-zag…

QuestionStereochemistry / Fischer and zig-zag projections

The Fischer projection formula and its corresponding zig-zag projection for the erythro configuration of the following compound are respectively :

UPSC Combined Geo-Scientist Prelims 2025 Paper II (Chemistry), Q87: figure printed with the question
UPSC Combined Geo-Scientist Prelims 2025 Paper II (Chemistry), Q87: answer options as printed
  1. (a) Fischer: HO and CH₃HN both on the left (H's on the right), Ar on top, CH₃ at bottom; zig-zag: OH wedged at C1, NHCH₃ hashed at C2 with CH₃ continuing the chain
  2. (b) Fischer: HO and CH₃HN both on the left (H's on the right); zig-zag: OH wedged at C1, NHCH₃ in the chain at C2 with CH₃ hashed
  3. (c) Fischer: H–C–OH (OH right) over CH₃HN–C–H (NHCH₃ left); zig-zag: OH wedged at C1, NHCH₃ hashed at C2 with CH₃ continuing the chain
  4. (d) Fischer: H–C–OH (OH right) over CH₃HN–C–H (NHCH₃ left); zig-zag: OH wedged at C1, NHCH₃ in the chain at C2 with CH₃ hashed

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