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.
Reactions and rearrangements: every question, 2021 to 2025
26 parts worth 275 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.
(a) Pinacol-pinacolone, Hofmann, Beckmann, Baeyer-Villiger, Favorskii, Fries, Claisen, Cope, Stevens and Wagner-Meerwein rearrangements. (b) Aldol condensation, Claisen condensation, Dieckmann, Perkin, Knoevenagel, Wittig, Clemmensen, Wolff-Kishner, Cannizzaro and von Richter reactions; Stobbe, benzoin and acyloin condensations; Fischer indole synthesis, Skraup synthesis, Bischler-Napieralski, Sandmeyer, Reimer-Tiemann and Reformatsky reactions.
Notes: Molecular rearrangements (full notes) · short notes
Notes: Carbonyl additions and condensations (full notes) · short notes
2025
- Q2(a) Ester shift with sodium ethoxide; cyclisation of an epoxy-diene15 marks Question only
- Q2(c) Products of four reactions20 marks Question only
- Q3(a)(i) Products of two reactions10 marks Answered
2024
- Q1(d) Name and reagent for five conversions10 marks Answered
- Q2(b)(i) Benzaldehyde with diethyl malonate and pyridine10 marks Question only
- Q2(c)(i) Products of three reactions15 marks Question only
- Q2(c)(ii) 2-Methylpent-2-enoic acid by the Reformatsky reaction5 marks Question only
- Q4(c)(i) Major products of three rearrangements10 marks Question only
- Q4(c)(ii) Chlorodifluoromethyl phenyl ketone with Ac₂O / AcONa10 marks Question only
- Q8(b)(i) Ring opening of 2,2-dimethylcyclopropanone by methoxide10 marks Answered
2023
- Q1(e)(i) 2-Chloro-6-methylcyclohexanone with methoxide5 marks Answered
- Q1(e)(ii) Name reaction that gives nitrogen as a by-product5 marks Answered
- Q4(b) Cyclic benzylammonium salt with NaNH₂ / NH₃10 marks Question only
- Q4(c)(i) Crossed aldol: butanone and acetaldehyde10 marks Question only
- Q4(c)(ii) Benzonitrile from benzene10 marks Question only
2022
- Q1(c) The reaction that is not a condensation, and its mechanism10 marks Answered
- Q1(d) Acid-catalysed rearrangement of two phenyl-substituted 1,2-diols10 marks Answered
- Q2(a) Products X and Y in three reactions15 marks Question only
- Q2(c)(i) Matching three heterocycle syntheses; mechanism of the indole synthesis10 marks Question only
- Q2(c)(ii) L-Dopa from L-tyrosine10 marks Question only
- Q4(c) Phenol to coumarin20 marks Answered
2021
- Q1(b) Benzyltrimethylammonium salt with sodium amide at low and at high temperature10 marks Answered
- Q3(a)(i) 1-(Hydroxydiphenylmethyl)cyclopentanol with conc. H₂SO₄10 marks Answered
- Q3(a)(ii) 1-Acetyl-1-chloro-4-methylcyclohexane with ethoxide10 marks Answered
- Q4(c)(i) A Wittig reaction and a Fischer indole synthesis10 marks Question only
- Q4(c)(ii) Pairs that give an α,β-unsaturated carbonyl compound with base5 marks Question only
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