= Solution
\Image[/past-exam-of-the-chemistry-course-of-the-year-3-of-the-natural-sciences-course-of-the-university-of-cambridge/2022/paper-3-q39-ring-assignments.png]
{title=Cyclohexene assignments with explicit ambiguity for the overlapping allylic methylenes}
Number ring positions $r_1$ through $r_6$ around the ring, with $r_1=r_2$ the double bond. These auxiliary ring-position labels are distinct from the printed carbon-signal numbers.
* \b[$r_1$:] quaternary <alkene> <carbon> \b[4], attached to the OCH$_2$ side chain.
* \b[$r_2$:] <alkene> CH \b[8], proton \b[E].
* \b[$r_3$:] allylic CH$_2$, one of <carbon> signals \b[14/15]; its protons are \b[K and one of G/H/I].
* \b[$r_4$:] methine \b[12], proton \b[L], attached to the tertiary-alcohol <carbon> 10.
* \b[$r_5$:] CH$_2$ \b[17], protons \b[J and M].
* \b[$r_6$:] the other allylic CH$_2$ \b[15/14], carrying the remaining \b[two of G/H/I].
The <HSQC> pairs J and M with 17 and places L on 12. It also places K and one unresolved member of G/H/I on one of the closely spaced allylic carbons, with the other two G/H/I protons on the other. <COSY> connects the vinylic E to the adjacent allylic part and connects the methine L to its neighboring methylenes; <HMBC> links F to the substituted <alkene> end and the gem-dimethyl group to the methine end.
The printed overlap does not justify a unique assignment of every G/H/I letter or a forced 14-versus-15 assignment to those two ring positions. The drawing retains those alternatives explicitly. In the half-chair, L is pseudoaxial; the resolved large/small couplings are consistent with pseudoaxial/pseudoequatorial methylene partners, but exact axial letter labels within the overlapped group remain uncertain.
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