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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 · 2021 · Paper II

Q5(b)(i). Three para-substituted styrenes in anionic polymerisation

Question

Arrange the monomers I (p-methylstyrene), II (p-nitrostyrene) and III (p-methoxystyrene) in order of decreasing ability to undergo anionic polymerisation. [structures given in the paper]

Answer in brief

II > I > III (p-NO₂ > p-CH₃ > p-OCH₃).

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Topic notes: polymers: polymerisation, Ziegler–Natta and molar mass, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversanionic polymerisationsubstituted styrenebenzylic carbanionHammett sigmaelectron-withdrawing group

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