Q8(b)(i). Ring opening of 2,2-dimethylcyclopropanone by methoxide
2,2-Dimethylcyclopropanone undergoes ring opening when attacked by methoxide ion, and the product has the following spectral data: IR (ν, cm⁻¹): 1740, 1160; ¹H NMR (δ): 3.6 (3H, s), 1.2 (9H, s); Mass (m/z): 116, 85, 59, 31. Deduce the structure of the product with reasons. Write down the structure of another possible product.
Answer in brief
Product: methyl 2,2-dimethylpropanoate (methyl pivalate), (CH₃)₃C–COOCH₃. Other possible product: methyl 3-methylbutanoate.
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CoverscyclopropanoneFavorskii rearrangementmethyl pivalatespectral structure deductioncarbanion stability
All parts of Question 8
- 8(a) Assignment of four C=O stretching bands15 marks
- 8(b)(i) Ring opening of 2,2-dimethylcyclopropanone by methoxide10 marks
- 8(b)(ii) Order of J(Ha–Hb)5 marks
- 8(c)(i) Two alkenes from 2-chloro-2,3-dimethylbutane10 marks
- 8(c)(ii) Fragmentation of diethyl ether5 marks
- 8(c)(iii) Bond length of HCl from its moment of inertia5 marks