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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 · 2022 · Paper II

Q5(b). Photolysis of 2-methylcyclohexanone in solution

Question

Write down the products obtained after photolysis of 2-methylcyclohexanone in solution phase. Explain the formation of products.

Answer in brief

Norrish type I cleavage of the C-1–C-2 bond gives an acyl–alkyl biradical; hydrogen transfer then gives hept-5-enal (major) and a ketene trapped by solvent as heptanoic acid or its ester; CO loss is minor.

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Topic notes: organic photochemistry and Norrish reactions, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversNorrish type Iα-cleavagephotolysis2-methylcyclohexanonebiradicalketene

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