Question

How many unique 'H NMR signals exist in the spectrum for the following compound? Number 3 Incorrect There are fewer unique proton signals than you have indicated. Consider the plane of symmetry perpendicular to the screen and containing the double bond. Which protons are equivalent because of the symmetry?

Answer 1

There are only two unique signals. It depends on the total no.of hydrogen present with the different environment around them.

If we look carefully, the two methyl groups have a total of 6 hydrogens, but all 6 will give the same signal because there's a plane of symmetry and there are two carbons attached to end carbon of C=C, they both will give the same signal. Whereas the central carbon did not have any hydrogens. Hence there are a total of two unique signals.

H H Hн Н

IN the diagram, all hydrogens present in a circle will have the same frequency.