Indian Forest Service (Mains), Chemistry optional · 2025 · Paper II
Q8(c). Metalation of thiophene
Question
Why does thiophene metalate as readily as furan despite sulfur being less electronegative?
Answer in brief
α Deprotonation is favoured by sulfur's polarisability and stabilisation of the adjacent carbanion, together with coordination/aggregation effects of the metal reagent.
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The full model answer
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Coversmetalation of thiophenen-BuLi lithiationthiophene vs furanα-carbanion stabilisationpolarisability of sulfur
All parts of Question 8
- 8(a)(i) CO rotational constant and bond length10 marks
- 8(a)(ii) Isotopic change in rotational constant5 marks
- 8(b)(i) Isotope exchange and zero-point energy10 marks
- 8(b)(ii) Hot-band population in iodine10 marks
- 8(c) Metalation of thiophene5 marks