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UPSC Combined Geo-Scientist

Chemist

  • 3 descriptive papers
  • 200 marks each
  • 3 h per paper

Mains Paper III covers analytical and organic chemistry.

UPSC Combined Geo-Scientist, Mains · 2023 · Mains Paper III

Q7(c). Photochemical ring opening of 8-methyl-1-decalone: Norrish Type II

Question

Predict the mechanism of the following photochemical conversion. Name the reaction and give justification. [Structures of the ketone and its photoproduct (hν) given in the paper]

Answer in brief

Norrish Type II reaction (photoelimination): the excited C=O abstracts a γ-hydrogen, the 1,4-biradical breaks its α–β bond, and the enol formed goes to the ketone.

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

CoversNorrish Type IIphotochemistry of ketonesγ-hydrogen abstraction1,4-biradicalphotoelimination

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