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UPSC Civil Services (Mains)

Chemistry optional

  • 2 papers
  • 250 marks each
  • 3 h per paper
  • 5 of 8 questions, Q1 and Q5 compulsory

Paper II covers organic chemistry and spectroscopy.

UPSC Civil Services (Mains), Chemistry optional · 2023 · Paper II

Q2(a)(i). Aromatic, antiaromatic or non-aromatic by the Hückel rule

Question

Based on Hückel rule, predict the above compounds as aromatic, antiaromatic and non-aromatic. [structures (A), (B), (C) given in the paper]

Answer in brief

(A) Cyclopentadiene: non-aromatic. (B) 1-Methylborole: antiaromatic. (C) 1-Methylphosphole: aromatic.

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Topic notes: aromaticity (Hückel rule, antiaromaticity, annulenes, azulene, tropolone, fulvene, sydnones), with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversHückel rulearomaticityantiaromaticityborolephosphole

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