Indian Forest Service (Mains), Chemistry optional · 2024 · Paper II

Q7(b)(ii). Woodward–Fieser estimates for two tetraenes

5 marks
Topic: Principles of spectroscopy and applications in structure elucidation
Question only

Question

Estimate the absorption maxima for the two drawn steroidal conjugated polyenes. [structures of two steroidal tetraenes given in the paper]

Model answer

The free solution for 2024 answers questions 1, 2, 4, 5 and 8, the ones picked in its time plan. This part is not answered on the site yet. New answers are announced on Telegram.

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Topic notes: UV spectroscopy and Woodward–Fieser rules, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversWoodward-Fieser rulesλmax calculationconjugated polyeneshomoannular dienesteroid UV

All parts of Question 7

7(a)(i) Hydroboration followed by carbonylation5 marks
7(a)(ii) Thermal organoborane isomerization5 marks
7(b)(i) UV bands of a ketone and an enone10 marks
7(b)(ii) Woodward–Fieser estimates for two tetraenes5 marks
7(c) Identification of an amino ester15 marks