Q8(c)(i). Two alkenes from 2-chloro-2,3-dimethylbutane
2-Chloro-2,3-dimethylbutane on dehydrohalogenation can give two products. Explain how the two can be distinguished using ¹H NMR and IR spectral data.
Answer in brief
Products: 2,3-dimethylbut-2-ene (A, Saytzeff) and 2,3-dimethylbut-1-ene (B, Hofmann). A shows one NMR singlet and no alkene bands in IR; B shows four sets of signals and =CH₂ bands.
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CoversdehydrohalogenationSaytzeff ruleHofmann product2,3-dimethylbut-2-eneIR and NMR distinction
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