UPSC Civil Services (Mains), Chemistry optional · 2022 · Paper II
Q2(a). Products X and Y in three reactions
Question
Predict the products X and Y in the following reactions: (i) (1) O₃, (2) H₂O₂ gives X + Y; (ii) PBr₃, Br₂ gives X; (iii) Br₂/hν at 127 °C gives X + Y. [structures of the three substrates given in the paper]
Model answer
The free solution for 2022 answers questions 1, 4, 5, 6 and 8, the ones picked in its time plan. Question 2 is answered in full in the Chemistry Paper II, 2021 to 2025 book, with every part of every paper.
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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
CoversozonolysisHell–Volhard–Zelinsky reactionradical brominationselectivity of brominationoxidative work-up
All parts of Question 2
- 2(a) Products X and Y in three reactions15 marks
- 2(b)(i) 2,2-Dimethyltetrahydrofuran with one equivalent of HI5 marks
- 2(b)(ii) 1,2-Dihydronaphthalene with NBS, then sodium ethoxide5 marks
- 2(b)(iii) Alkenes from 2-chloro-2,3-dimethylpentane with sodium ethoxide5 marks
- 2(c)(i) Matching three heterocycle syntheses; mechanism of the indole synthesis10 marks
- 2(c)(ii) L-Dopa from L-tyrosine10 marks