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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 · 2020 · Paper II, Chemistry · Q97 of 120

Geo-Scientist Prelims 2020 Chemistry Q97: Two compounds [X] and [Y] are given below:

QuestionStereochemistry / Newman projections

Two compounds [X] and [Y] are given below:

UPSC Combined Geo-Scientist Prelims 2020 Paper II (Chemistry), Q97: figure printed with the question

The relationship between [X] and [Y] is:

  1. (a) Identical
  2. (b) Diastereomers
  3. (c) Enantiomers
  4. (d) Constitutional isomers

Answer: (c) Enantiomers

Both are butan-2-ol. On the stereocentre, H and the ethyl carbon keep their places while OH and CH₃ swap between [X] and [Y]. One swap = inverted configuration → enantiomers → (c).

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