Indian Forest Service (Mains)
Chemistry optional
- 2 papers
- 200 marks each
- 3 h per paper
Paper II covers organic chemistry and spectroscopy.
All topics
Paper II, organic chemistry and spectroscopy
Pericyclic reactions: every question, 2021 to 2025
16 parts worth 105 marks have been set on this unit in UPSC IFoS Chemistry Paper II from 2021 to 2025. Each one opens on its own page with the question, the answer in brief and the key points.
Syllabus
Classification and examples; Woodward-Hoffmann rules: electrocyclic reactions, cycloaddition reactions [2+2 and 4+2] and sigmatropic shifts [1, 3; 3, 3 and 1, 5], FMO approach.
Notes: Pericyclic reactions (full notes) · short notes
2025
- Q1(g) Two thermal electrocyclic steps5 marks Answered
- Q2(d) Thermal oxygen–sulfur interchange10 marks Question only
2024
- Q1(g) Photochemical alkyl migration5 marks Answered
- Q3(c)(i) Endo selectivity in a Diels–Alder reaction10 marks Question only
- Q3(c)(ii) Electrocyclic closure of an E,Z diene5 marks Question only
2023
- Q1(g) A double oxy-Cope rearrangement5 marks Answered
- Q3(f) Six-pi electrocyclic switching10 marks Question only
- Q4(c) Regioselective Diels–Alder addition5 marks Question only
2022
- Q3(b) Steric control of Diels–Alder reactivity5 marks Answered
- Q4(e) Thermal–photochemical–thermal switching5 marks Question only
2021
- Q1(b) Photochemical hydrogen migration in a diene5 marks Answered
- Q2(a) Thermal closure of octatriene10 marks Answered
- Q4(a)(i) Cyclopentadiene and methyl acrylate5 marks Question only
- Q4(a)(ii) Tetraphenylcyclopentadienone cycloaddition5 marks Question only
- Q5(c) Vinylcyclopropane rearrangement5 marks Answered
- Q7(b) Ireland–Claisen rearrangement of an allylic acetate10 marks Question only