Question

In the above compound, the number of \(^1H\) NMR signals is

Hint:

When dealing with bicyclic or symmetric molecules, find the symmetry elements first to simplify the problem to one repeating unit.

Answer 1

{Step 1: Understanding the Concept:}
Chemical equivalence in NMR is determined by the symmetry of the molecule. Each unique environment of protons produces one signal.
{Step 2: Detailed Explanation:}
The molecule is 1,1'-bi(cyclohex-1-en-1-yl). It has a \(C_2\) axis or a center of inversion, making both rings identical. We analyze unique protons in one ring:
1. Vinyl proton (C2-H): Adjacent to the connecting bond. (Signal 1)
2. Allylic protons (C3-\(H_2\)): Adjacent to the vinyl proton. (Signal 2)
3. Homoallylic protons (C4-\(H_2\)): (Signal 3)
4. Homoallylic protons (C5-\(H_2\)): In a different environment than C4. (Signal 4)
5. Allylic protons (C6-\(H_2\)): Adjacent to the quaternary carbon. (Signal 5)
{Step 3: Final Answer:}
The number of signals is 5.