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
Pages 1 and 2 of 26 
Pages 3 and 4 of 26 
Pages 5 and 6 of 26
Pages 7 and 8 of 26 Pages 9 and 10 of 26 Pages 11 and 12 of 26 Pages 13 and 14 of 26 Pages 15 and 16 of 26 Pages 17 and 18 of 26 Pages 19 and 20 of 26 Pages 21 and 22 of 26 Pages 23 and 24 of 26 Pages 25 and 26 of 26 
Paper II, organic chemistry and spectroscopy
Solution, 2023
UPSC Civil Services (Mains), Chemistry optional. 26 pages. Questions 1, 2, 3, 5 and 8 are answered.
Every question of 2023, one page each50 parts in 8 questions, with the question as text and the key points of its answer
Question 1 50 marks
- 1(a)(i)Acidity of cyclopentadiene5 marks
- 1(a)(ii)Hydrogen exchange in cyclopropyl and cyclopropenyl ketones5 marks
- 1(b)(i)IUPAC name with stereodescriptors5 marks
- 1(b)(ii)Dimerisation ability of three triarylmethyl-type radicals5 marks
- 1(c)Methyl iodide with sodium azide: DMF against methanol10 marks
- 1(d)Photochemical electrocyclic closure of two cyclonona-1,3-dienes10 marks
- 1(e)(i)2-Chloro-6-methylcyclohexanone with methoxide5 marks
- 1(e)(ii)Name reaction that gives nitrogen as a by-product5 marks
Question 2 50 marks
- 2(a)(i)Aromatic, antiaromatic or non-aromatic by the Hückel rule5 marks
- 2(a)(ii)Primary and secondary kinetic isotope effects5 marks
- 2(a)(iii)Enolates of butan-2-one: NaOMe versus LDA5 marks
- 2(b)(i)Hydrolysis of bis(2-chloroethyl) sulfide and of 1,5-dichloropentane5 marks
- 2(b)(ii)Both glycosyl bromides give the β-glycoside5 marks
- 2(b)(iii)Ketene, hν, then cis-but-2-ene10 marks
- 2(c)(i)Acetolysis of 2-(cyclopent-3-enyl)ethyl tosylate10 marks
- 2(c)(ii)Indole: electrophilic substitution at C-3, not C-25 marks
Question 3 50 marks
Question 4 50 marks
- 4(a)(i)Norbornene with D–Br5 marks
- 4(a)(ii)Relative rates of bromination in methanol5 marks
- 4(a)(iii)Hydroboration–oxidation of a tetrasubstituted alkene10 marks
- 4(b)Cyclic benzylammonium salt with NaNH₂ / NH₃10 marks
- 4(c)(i)Crossed aldol: butanone and acetaldehyde10 marks
- 4(c)(ii)Benzonitrile from benzene10 marks
Question 5 50 marks
- 5(a)Number of ¹H NMR signals in (A) and (B)10 marks
- 5(b)C=C stretch of methylenecyclopropane and methylenecyclobutane10 marks
- 5(c)Acetylene to neoprene; why rubber perishes in air10 marks
- 5(d)LiAlH₄ reduction of camphor: OH cis to the bridge10 marks
- 5(e)Photolysis of acetone: vapour phase and room temperature10 marks
Question 6 50 marks
- 6(a)(i)Energy change of HCl + D₂ → DCl + HD10 marks
- 6(a)(ii)C=O bands of butyric acid, its ethyl ester and its anhydride5 marks
- 6(b)(i)Products A, B and C10 marks
- 6(b)(ii)Tacticity: isotactic, syndiotactic and atactic polymers5 marks
- 6(c)(i)Structure of C₁₆H₂₅NO from IR and ¹H NMR10 marks
- 6(c)(ii)Order of chemical shift of the lettered protons10 marks
Question 7 50 marks
- 7(a)2′-Deoxycytidine-3′-monophosphate; acidity; duplex stability; G≡C pairing15 marks
- 7(b)(i)Vapour-phase photolysis of cyclopentanone10 marks
- 7(b)(ii)Direct and benzophenone-sensitised photolysis of 1,3-butadiene5 marks
- 7(c)(i)Structures of (A), (B), (C), (D) and (E)10 marks
- 7(c)(ii)Osmate ester from cyclohexene; oxidation state and geometry of osmium5 marks
- 7(c)(iii)D-Mannitol: cyclohexylidene ketal, then HIO₄5 marks
Question 8 50 marks
- 8(a)(i)Doxepin: site of ionisation, m/z 58 ion and metastable ion10 marks
- 8(a)(ii)Ketone C₇H₁₂O with λmax = 249 nm5 marks
- 8(b)(i)Microwave activity; rotational constants of CO10 marks
- 8(b)(ii)Expected J(Ha–Hb) in three alkenes5 marks
- 8(c)(i)Keto and enol percentages of acetylacetone from integration10 marks
- 8(c)(ii)Two isomeric amides C₅H₁₁NO by mass spectrometry5 marks
- 8(c)(iii)Fundamental vibrations of CO₂ and their IR activity5 marks
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Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
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Printed copy and Kindle
UPSC Civil Services (Main) Chemistry Paper II: Model Answers 2021 to 2025
The book has all five years of Paper II in one volume, with every question printed above its answer, mechanisms labelled on the scheme, the topic-wise weightage of marks and a topic-wise index.