1H-NMR spectrum.?

Question

The structures of two compounds and the measured approximate ratio of 1H-NMR spectrum signal areas for one of the compounds are shown on the left.

Select which compound was responsible for the 1H-NMR spectrum.



Ratio of 1H-NMR spectrum signal areas = 33:33:33
1,3-cyclopentdiene
or
pentane


Ratio of 1H-NMR spectrum signal areas = 43:29:29
1-florocyclohextriene
or
hexane

Answer 1

1,3- cyclopentadiene has a plane of symmetry perpendicular to the plane of the ring, passing from C-5 and the middle of the C2-C3 bond. Thus you have 3 types of H, with a ratio of
2:2:2 =1:1:1

For pentane CH3CH2-CH2-CH2CH3 the plane of symmetry passes through C3, so you have again 3 types of H with ratio
6:4:2= 3:2:1

So the spectrum with 33:33:33 =1:1:1 corresponds to cyclopentadiene


1-fluoro-cyclohexatriene, is actually fluoro-benzene. You have a plane of symmetry passing through C1 and C4, so you have 3 types of H with ratio 2:2:1

For hexane CH3CH2CH2-CH2CH2CH3, so you see that the symmetry is such that we have 3 types of H with ratio 6:4:4=3:2:2 = 1.5:1:1

43:29:29 =1.48:1:1 so it is hexane.

Answer 2

I did not see the spectrum , But i suppose it is the second compound since in the first the sufaces would be equivalent