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.
All years
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Paper II, organic chemistry and spectroscopy
Question paper, 2025
UPSC Civil Services (Mains), Chemistry optional. 16 pages, as issued by UPSC.
Every question of 2025, one page each48 parts in 8 questions, with the question as text and the key points of its answer
Question 1 50 marks
Question 2 50 marks
Question 3 50 marks
- 3(a)(i)Products of two reactions10 marks
- 3(a)(ii)Ketone A from isobutanol alone5 marks
- 3(b)(i)Cyclopropane from tert-butyl chloroacetate and ethyl acrylate10 marks
- 3(b)(ii)Structures of C and D5 marks
- 3(c)(i)Missing reagents and intermediate10 marks
- 3(c)(ii)Photolysis of the α-diazoketone in methanol10 marks
Question 4 50 marks
- 4(a)(i)Molecular weight of poly(p-hydroxybenzoic acid)7 marks
- 4(a)(ii)Structure of the polymer3 marks
- 4(a)(iii)Precursor of natural rubber5 marks
- 4(b)(i)Nylon 6 and nylon 6,6 compared5 marks
- 4(b)(ii)Preparing syndiotactic polystyrene5 marks
- 4(b)(iii)Salient features of the α-helix5 marks
- 4(c)(i)Two dichlorides with NaN₃: neighbouring sulfur10 marks
- 4(c)(ii)Kinetic and thermodynamic enolates trapped with D₂O10 marks
Question 5 50 marks
Question 6 50 marks
- 6(a)(i)Products and intermediates of two reductions10 marks
- 6(a)(ii)Role of NMO in catalytic dihydroxylation5 marks
- 6(b)Three numericals15 marks
- 6(c)(i)Benzene to fulvene by light5 marks
- 6(c)(ii)Quantum yield of photobromination5 marks
- 6(c)(iii)Photolysis of 4,5-dimethylhexan-2-one5 marks
- 6(c)(iv)A, B and C from the mixed ketones5 marks
Question 7 50 marks
- 7(a)(i)Two UV bands of acetone5 marks
- 7(a)(ii)λmax by the Woodward–Fieser rules10 marks
- 7(b)(i)Diels–Alder reactivity of four dienes10 marks
- 7(b)(ii)2-Methoxybutadiene with acrylonitrile5 marks
- 7(c)(i)Rearrangement of a cis-divinylcyclopropane10 marks
- 7(c)(ii)Mode of ring closure in two electrocyclic reactions10 marks
Question 8 50 marks
- 8(a)(i)Coupling constants of the lettered protons5 marks
- 8(a)(ii)Chemical shifts of Hᵃ and Hᵇ5 marks
- 8(a)(iii)Number of ¹H NMR signals5 marks
- 8(b)(i)Structure of the halogenated ester10 marks
- 8(b)(ii)C₆H₁₂ alkenes with peaks at m/z 42 and 565 marks
- 8(c)(i)Characteristic fragment ions10 marks
- 8(c)(ii)Structure of C₄H₅NO₂10 marks