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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)(ii). Structures and configurations of natural and synthetic rubber

Question

Draw the structures of synthetic rubber and natural rubber and discuss their configurations.

Answer in brief

Natural rubber is cis-1,4-polyisoprene (all Z); synthetic rubbers are 1,4-polydienes such as neoprene (mainly trans) and Buna-S (mixed cis and trans units).

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The full model answer

As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.

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

Coversnatural rubbercis-1,4-polyisoprenegutta-perchaneopreneBuna-SZiegler–Natta

All parts of Question 5