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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(c). Acetophenone with SeO₂; benzoic acid with Na in liquid NH₃

Question

Predict the product(s) and suggest a mechanism in each of the following chemical transformations: I. Acetophenone with SeO₂. II. Benzoic acid with Na, NH₃ and C₂H₅OH.

Answer in brief

I. Phenylglyoxal, C₆H₅COCHO (α-CH₃ oxidised to CHO); II. cyclohexa-2,5-diene-1-carboxylic acid (1,4-dihydrobenzoic acid) by Birch reduction.

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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: reagents for oxidation, reduction and hydroboration, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversRiley oxidationselenium dioxidephenylglyoxalBirch reductionbenzoic aciddissolving metal reduction

All parts of Question 5