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.
Reaction mechanisms: every question, 2021 to 2025
6 parts worth 50 marks have been set on this unit in UPSC CSE 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.
General methods (both kinetic and non-kinetic) of study of mechanism of organic reactions: isotopic method, cross-over experiment, intermediate trapping, stereochemistry; energy of activation; thermodynamic control and kinetic control of reactions.
Notes: Methods of studying reaction mechanisms: isotopes, crossover, trapping, kinetic isotope effect (full notes) · short notes
Notes: Stereochemistry and conformational analysis: R/S, E/Z, Fischer and Newman projections, cyclohexane (full notes) · short notes
2025
- Q4(c)(ii) Kinetic and thermodynamic enolates trapped with D₂O10 marks Question only
2024
- Q2(a)(i) kH/kD = 7.1 for 2-phenylethyl bromide with ethoxide10 marks Question only
- Q4(b)(i) Crossover experiment for the Claisen rearrangement10 marks Question only
2023
- Q2(a)(ii) Primary and secondary kinetic isotope effects5 marks Answered
- Q2(a)(iii) Enolates of butan-2-one: NaOMe versus LDA5 marks Answered
2021
- Q1(a) Origin of the CN group in RCOO⁻ + BrCN10 marks Answered
UPSC Civil Services (Main) Chemistry Paper II: Model Answers 2021 to 2025
- All eight questions of each paper, with the question printed above its answer
- Mechanisms drawn out and labelled on the scheme
- Topic-wise weightage and a topic-wise index