UPSC Combined Geo-Scientist, Mains · 2026 · Mains Paper III
Q9(a). Diels–Alder of a quinone; ring opening and cycloaddition of a cyclobutene
Question
Draw the major products formed in the following reactions and describe the process involved: (i) 2-methyl-5-methoxy-1,4-benzoquinone + 1-methoxybuta-1,3-diene, heat → X; (ii) 1-methoxy-2-(phenylthio)cyclobutene, heat → Y; Y + maleic anhydride, heat → Z.
Model answer
The free solution for 2026 answers the questions picked in its time plan. Question 9 is answered in full in the Book Edition of the 2026 solutions of Geo-Scientist Chemistry Paper III.
CoversDiels–Alder, electrocyclic ring openingDiels–Alder of a quinonering opening and cycloaddition of a cyclobutene
All parts of Question 9
- 9(a) Diels–Alder of a quinone; ring opening and cycloaddition of a cyclobutene10 marks
- 9(b) Ionone mass spectrum; HWE, DIBAL-H and Sharpless sequence10 marks
- 9(c) Ziegler–Natta polymerisation of ethylene10 marks