How many peaks would there be in H1 NMR of ethene?

Since the bonds can't rotate, would there be 2 peaks? Likewise, how many peaks would there be in *trans*-but-2-ene and *cis*-but-2-ene?




You need to consider whether the protons in ethene are chemically equivalent, magnetically equivalent, or both. The lewis structure of ethene:


[![Lewis structure of ethene](https://i.stack.imgur.com/rROox.png)](https://i.stack.imgur.com/rROox.png)


Because of the *symmetry* of the planar ethene molecule, all H atoms are chemically and magnetically equivalent. The spin system is therefore **A$\_4$**. The signal is *not* split because the environment is the same for all H atoms. The signal would therefore be a single peak. Compared to an "average" methyl group, the ethylene protons are less shielded, and would appear at a higher chemical shift than methyl groups.


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