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Indian Forest Service (Mains)

Chemistry optional

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

Paper II covers organic chemistry and spectroscopy.

Indian Forest Service (Mains), Chemistry optional · 2024 · Paper II

Q2(a)(ii). Kinetic and thermodynamic enolates

Question

Predict the reactive species from the drawn unsymmetrical ketone with (i) LDA at −78 °C and (ii) alkoxide, and explain the control. [structure given in the paper]

Answer in brief

LDA at low temperature usually gives the less substituted kinetic enolate; reversible alkoxide conditions favour the more substituted thermodynamic enolate.

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Topic notes: methods of studying mechanisms (isotopic labelling, crossover, trapping, kinetic isotope effect, kinetic and thermodynamic control), with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverskinetic enolatethermodynamic enolateLDA −78 °Ckinetic vs thermodynamic controldirected aldol

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